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2020-09-29bpf: Move prog->aux->linked_prog and trampoline into bpf_link on attachToke Høiland-Jørgensen7-253/+289
In preparation for allowing multiple attachments of freplace programs, move the references to the target program and trampoline into the bpf_tracing_link structure when that is created. To do this atomically, introduce a new mutex in prog->aux to protect writing to the two pointers to target prog and trampoline, and rename the members to make it clear that they are related. With this change, it is no longer possible to attach the same tracing program multiple times (detaching in-between), since the reference from the tracing program to the target disappears on the first attach. However, since the next patch will let the caller supply an attach target, that will also make it possible to attach to the same place multiple times. Signed-off-by: Toke Høiland-Jørgensen <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-29bpf/preload: Make sure Makefile cleans up after itself, and add .gitignoreToke Høiland-Jørgensen2-0/+6
The Makefile in bpf/preload builds a local copy of libbpf, but does not properly clean up after itself. This can lead to subsequent compilation failures, since the feature detection cache is kept around which can lead subsequent detection to fail. Fix this by properly setting clean-files, and while we're at it, also add a .gitignore for the directory to ignore the build artifacts. Fixes: d71fa5c9763c ("bpf: Add kernel module with user mode driver that populates bpffs.") Signed-off-by: Toke Høiland-Jørgensen <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-28bpf: Add bpf_seq_printf_btf helperAlan Maguire2-2/+3
A helper is added to allow seq file writing of kernel data structures using vmlinux BTF. Its signature is long bpf_seq_printf_btf(struct seq_file *m, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags); Flags and struct btf_ptr definitions/use are identical to the bpf_snprintf_btf helper, and the helper returns 0 on success or a negative error value. Suggested-by: Alexei Starovoitov <[email protected]> Signed-off-by: Alan Maguire <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-28bpf: Bump iter seq size to support BTF representation of large data structuresAlan Maguire1-2/+2
BPF iter size is limited to PAGE_SIZE; if we wish to display BTF-based representations of larger kernel data structures such as task_struct, this will be insufficient. Suggested-by: Alexei Starovoitov <[email protected]> Signed-off-by: Alan Maguire <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-28bpf: Add bpf_snprintf_btf helperAlan Maguire2-0/+5
A helper is added to support tracing kernel type information in BPF using the BPF Type Format (BTF). Its signature is long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags); struct btf_ptr * specifies - a pointer to the data to be traced - the BTF id of the type of data pointed to - a flags field is provided for future use; these flags are not to be confused with the BTF_F_* flags below that control how the btf_ptr is displayed; the flags member of the struct btf_ptr may be used to disambiguate types in kernel versus module BTF, etc; the main distinction is the flags relate to the type and information needed in identifying it; not how it is displayed. For example a BPF program with a struct sk_buff *skb could do the following: static struct btf_ptr b = { }; b.ptr = skb; b.type_id = __builtin_btf_type_id(struct sk_buff, 1); bpf_snprintf_btf(str, sizeof(str), &b, sizeof(b), 0, 0); Default output looks like this: (struct sk_buff){ .transport_header = (__u16)65535, .mac_header = (__u16)65535, .end = (sk_buff_data_t)192, .head = (unsigned char *)0x000000007524fd8b, .data = (unsigned char *)0x000000007524fd8b, .truesize = (unsigned int)768, .users = (refcount_t){ .refs = (atomic_t){ .counter = (int)1, }, }, } Flags modifying display are as follows: - BTF_F_COMPACT: no formatting around type information - BTF_F_NONAME: no struct/union member names/types - BTF_F_PTR_RAW: show raw (unobfuscated) pointer values; equivalent to %px. - BTF_F_ZERO: show zero-valued struct/union members; they are not displayed by default Signed-off-by: Alan Maguire <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-28bpf: Move to generic BTF show support, apply it to seq files/stringsAlan Maguire1-102/+905
generalize the "seq_show" seq file support in btf.c to support a generic show callback of which we support two instances; the current seq file show, and a show with snprintf() behaviour which instead writes the type data to a supplied string. Both classes of show function call btf_type_show() with different targets; the seq file or the string to be written. In the string case we need to track additional data - length left in string to write and length to return that we would have written (a la snprintf). By default show will display type information, field members and their types and values etc, and the information is indented based upon structure depth. Zeroed fields are omitted. Show however supports flags which modify its behaviour: BTF_SHOW_COMPACT - suppress newline/indent. BTF_SHOW_NONAME - suppress show of type and member names. BTF_SHOW_PTR_RAW - do not obfuscate pointer values. BTF_SHOW_UNSAFE - do not copy data to safe buffer before display. BTF_SHOW_ZERO - show zeroed values (by default they are not shown). Signed-off-by: Alan Maguire <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-28bpf: Provide function to get vmlinux BTF informationAlan Maguire1-6/+12
It will be used later for BPF structure display support Signed-off-by: Alan Maguire <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-28bpf: verifier: refactor check_attach_btf_id()Toke Høiland-Jørgensen2-87/+118
The check_attach_btf_id() function really does three things: 1. It performs a bunch of checks on the program to ensure that the attachment is valid. 2. It stores a bunch of state about the attachment being requested in the verifier environment and struct bpf_prog objects. 3. It allocates a trampoline for the attachment. This patch splits out (1.) and (3.) into separate functions which will perform the checks, but return the computed values instead of directly modifying the environment. This is done in preparation for reusing the checks when the actual attachment is happening, which will allow tracing programs to have multiple (compatible) attachments. This also fixes a bug where a bunch of checks were skipped if a trampoline already existed for the tracing target. Fixes: 6ba43b761c41 ("bpf: Attachment verification for BPF_MODIFY_RETURN") Fixes: 1e6c62a88215 ("bpf: Introduce sleepable BPF programs") Acked-by: Andrii Nakryiko <[email protected]> Signed-off-by: Toke Høiland-Jørgensen <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-28bpf: change logging calls from verbose() to bpf_log() and use log pointerToke Høiland-Jørgensen2-28/+28
In preparation for moving code around, change a bunch of references to env->log (and the verbose() logging helper) to use bpf_log() and a direct pointer to struct bpf_verifier_log. While we're touching the function signature, mark the 'prog' argument to bpf_check_type_match() as const. Also enhance the bpf_verifier_log_needed() check to handle NULL pointers for the log struct so we can re-use the code with logging disabled. Acked-by: Andrii Nakryiko <[email protected]> Signed-off-by: Toke Høiland-Jørgensen <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-28bpf: disallow attaching modify_return tracing functions to other BPF programsToke Høiland-Jørgensen1-0/+5
From the checks and commit messages for modify_return, it seems it was never the intention that it should be possible to attach a tracing program with expected_attach_type == BPF_MODIFY_RETURN to another BPF program. However, check_attach_modify_return() will only look at the function name, so if the target function starts with "security_", the attach will be allowed even for bpf2bpf attachment. Fix this oversight by also blocking the modification if a target program is supplied. Fixes: 18644cec714a ("bpf: Fix use-after-free in fmod_ret check") Fixes: 6ba43b761c41 ("bpf: Attachment verification for BPF_MODIFY_RETURN") Acked-by: Andrii Nakryiko <[email protected]> Signed-off-by: Toke Høiland-Jørgensen <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-28bpf: sockmap: Enable map_update_elem from bpf_iterLorenz Bauer1-1/+1
Allow passing a pointer to a BTF struct sock_common* when updating a sockmap or sockhash. Since BTF pointers can fault and therefore be NULL at runtime we need to add an additional !sk check to sock_map_update_elem. Since we may be passed a request or timewait socket we also need to check sk_fullsock. Doing this allows calling map_update_elem on sockmap from bpf_iter context, which uses BTF pointers. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-28bpf, cpumap: Remove rcpu pointer from cpu_map_build_skb signatureLorenzo Bianconi1-3/+2
Get rid of bpf_cpu_map_entry pointer in cpu_map_build_skb routine signature since it is no longer needed. Signed-off-by: Lorenzo Bianconi <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Link: https://lore.kernel.org/bpf/33cb9b7dc447de3ea6fd6ce713ac41bca8794423.1601292015.git.lorenzo@kernel.org
2020-09-28bpf: Enable BPF_PROG_TEST_RUN for raw_tracepointSong Liu1-1/+1
Add .test_run for raw_tracepoint. Also, introduce a new feature that runs the target program on a specific CPU. This is achieved by a new flag in bpf_attr.test, BPF_F_TEST_RUN_ON_CPU. When this flag is set, the program is triggered on cpu with id bpf_attr.test.cpu. This feature is needed for BPF programs that handle perf_event and other percpu resources, as the program can access these resource locally. Signed-off-by: Song Liu <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Acked-by: John Fastabend <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-25bpf, verifier: Remove redundant var_off.value ops in scalar known reg casesJohn Fastabend1-4/+2
In BPF_AND and BPF_OR alu cases we have this pattern when the src and dst tnum is a constant. 1 dst_reg->var_off = tnum_[op](dst_reg->var_off, src_reg.var_off) 2 scalar32_min_max_[op] 3 if (known) return 4 scalar_min_max_[op] 5 if (known) 6 __mark_reg_known(dst_reg, dst_reg->var_off.value [op] src_reg.var_off.value) The result is in 1 we calculate the var_off value and store it in the dst_reg. Then in 6 we duplicate this logic doing the op again on the value. The duplication comes from the the tnum_[op] handlers because they have already done the value calcuation. For example this is tnum_and(). struct tnum tnum_and(struct tnum a, struct tnum b) { u64 alpha, beta, v; alpha = a.value | a.mask; beta = b.value | b.mask; v = a.value & b.value; return TNUM(v, alpha & beta & ~v); } So lets remove the redundant op calculation. Its confusing for readers and unnecessary. Its also not harmful because those ops have the property, r1 & r1 = r1 and r1 | r1 = r1. Signed-off-by: John Fastabend <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-25bpf: Change bpf_sk_storage_*() to accept ARG_PTR_TO_BTF_ID_SOCK_COMMONMartin KaFai Lau1-2/+2
This patch changes the bpf_sk_storage_*() to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will work with the pointer returned by the bpf_skc_to_*() helpers also. A micro benchmark has been done on a "cgroup_skb/egress" bpf program which does a bpf_sk_storage_get(). It was driven by netperf doing a 4096 connected UDP_STREAM test with 64bytes packet. The stats from "kernel.bpf_stats_enabled" shows no meaningful difference. The sk_storage_get_btf_proto, sk_storage_delete_btf_proto, btf_sk_storage_get_proto, and btf_sk_storage_delete_proto are no longer needed, so they are removed. Signed-off-by: Martin KaFai Lau <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Lorenz Bauer <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-25bpf: Enable bpf_skc_to_* sock casting helper to networking prog typeMartin KaFai Lau1-2/+32
There is a constant need to add more fields into the bpf_tcp_sock for the bpf programs running at tc, sock_ops...etc. A current workaround could be to use bpf_probe_read_kernel(). However, other than making another helper call for reading each field and missing CO-RE, it is also not as intuitive to use as directly reading "tp->lsndtime" for example. While already having perfmon cap to do bpf_probe_read_kernel(), it will be much easier if the bpf prog can directly read from the tcp_sock. This patch tries to do that by using the existing casting-helpers bpf_skc_to_*() whose func_proto returns a btf_id. For example, the func_proto of bpf_skc_to_tcp_sock returns the btf_id of the kernel "struct tcp_sock". These helpers are also added to is_ptr_cast_function(). It ensures the returning reg (BPF_REF_0) will also carries the ref_obj_id. That will keep the ref-tracking works properly. The bpf_skc_to_* helpers are made available to most of the bpf prog types in filter.c. The bpf_skc_to_* helpers will be limited by perfmon cap. This patch adds a ARG_PTR_TO_BTF_ID_SOCK_COMMON. The helper accepting this arg can accept a btf-id-ptr (PTR_TO_BTF_ID + &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON]) or a legacy-ctx-convert-skc-ptr (PTR_TO_SOCK_COMMON). The bpf_skc_to_*() helpers are changed to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will accept pointer obtained from skb->sk. Instead of specifying both arg_type and arg_btf_id in the same func_proto which is how the current ARG_PTR_TO_BTF_ID does, the arg_btf_id of the new ARG_PTR_TO_BTF_ID_SOCK_COMMON is specified in the compatible_reg_types[] in verifier.c. The reason is the arg_btf_id is always the same. Discussion in this thread: https://lore.kernel.org/bpf/[email protected]/ The ARG_PTR_TO_BTF_ID_ part gives a clear expectation that the helper is expecting a PTR_TO_BTF_ID which could be NULL. This is the same behavior as the existing helper taking ARG_PTR_TO_BTF_ID. The _SOCK_COMMON part means the helper is also expecting the legacy SOCK_COMMON pointer. By excluding the _OR_NULL part, the bpf prog cannot call helper with a literal NULL which doesn't make sense in most cases. e.g. bpf_skc_to_tcp_sock(NULL) will be rejected. All PTR_TO_*_OR_NULL reg has to do a NULL check first before passing into the helper or else the bpf prog will be rejected. This behavior is nothing new and consistent with the current expectation during bpf-prog-load. [ ARG_PTR_TO_BTF_ID_SOCK_COMMON will be used to replace ARG_PTR_TO_SOCK* of other existing helpers later such that those existing helpers can take the PTR_TO_BTF_ID returned by the bpf_skc_to_*() helpers. The only special case is bpf_sk_lookup_assign() which can accept a literal NULL ptr. It has to be handled specially in another follow up patch if there is a need (e.g. by renaming ARG_PTR_TO_SOCKET_OR_NULL to ARG_PTR_TO_BTF_ID_SOCK_COMMON_OR_NULL). ] [ When converting the older helpers that take ARG_PTR_TO_SOCK* in the later patch, if the kernel does not support BTF, ARG_PTR_TO_BTF_ID_SOCK_COMMON will behave like ARG_PTR_TO_SOCK_COMMON because no reg->type could have PTR_TO_BTF_ID in this case. It is not a concern for the newer-btf-only helper like the bpf_skc_to_*() here though because these helpers must require BTF vmlinux to begin with. ] Signed-off-by: Martin KaFai Lau <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: John Fastabend <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-25bpf: Move the PTR_TO_BTF_ID check to check_reg_type()Martin KaFai Lau1-29/+31
check_reg_type() checks whether a reg can be used as an arg of a func_proto. For PTR_TO_BTF_ID, the check is actually not completely done until the reg->btf_id is pointing to a kernel struct that is acceptable by the func_proto. Thus, this patch moves the btf_id check into check_reg_type(). "arg_type" and "arg_btf_id" are passed to check_reg_type() instead of "compatible". The compatible_reg_types[] usage is localized in check_reg_type() now. The "if (!btf_id) verbose(...); " is also removed since it won't happen. Signed-off-by: Martin KaFai Lau <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Lorenz Bauer <[email protected]> Acked-by: John Fastabend <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-23Revert "bpf: Fix potential call bpf_link_free() in atomic context"Alexei Starovoitov1-2/+6
This reverts commit 31f23a6a181c81543b10a1a9056b0e6c7ef1c747. This change made many selftests/bpf flaky: flow_dissector, sk_lookup, sk_assign and others. There was no issue in the code. Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-23Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-nextDavid S. Miller9-235/+510
Alexei Starovoitov says: ==================== pull-request: bpf-next 2020-09-23 The following pull-request contains BPF updates for your *net-next* tree. We've added 95 non-merge commits during the last 22 day(s) which contain a total of 124 files changed, 4211 insertions(+), 2040 deletions(-). The main changes are: 1) Full multi function support in libbpf, from Andrii. 2) Refactoring of function argument checks, from Lorenz. 3) Make bpf_tail_call compatible with functions (subprograms), from Maciej. 4) Program metadata support, from YiFei. 5) bpf iterator optimizations, from Yonghong. ==================== Signed-off-by: David S. Miller <[email protected]>
2020-09-23bpf: Explicitly size compatible_reg_typesLorenz Bauer1-2/+1
Arrays with designated initializers have an implicit length of the highest initialized value plus one. I used this to ensure that newly added entries in enum bpf_reg_type get a NULL entry in compatible_reg_types. This is difficult to understand since it requires knowledge of the peculiarities of designated initializers. Use __BPF_ARG_TYPE_MAX to size the array instead. Suggested-by: Alexei Starovoitov <[email protected]> Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-22Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netDavid S. Miller2-12/+7
Two minor conflicts: 1) net/ipv4/route.c, adding a new local variable while moving another local variable and removing it's initial assignment. 2) drivers/net/dsa/microchip/ksz9477.c, overlapping changes. One pretty prints the port mode differently, whilst another changes the driver to try and obtain the port mode from the port node rather than the switch node. Signed-off-by: David S. Miller <[email protected]>
2020-09-21bpf: Use a table to drive helper arg type checksLorenz Bauer1-74/+109
The mapping between bpf_arg_type and bpf_reg_type is encoded in a big hairy if statement that is hard to follow. The debug output also leaves to be desired: if a reg_type doesn't match we only print one of the options, instead printing all the valid ones. Convert the if statement into a table which is then used to drive type checking. If none of the reg_types match we print all options, e.g.: R2 type=rdonly_buf expected=fp, pkt, pkt_meta, map_value Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Hoist type checking for nullable arg typesLorenz Bauer1-34/+30
check_func_arg has a plethora of weird if statements with empty branches. They work around the fact that *_OR_NULL argument types should accept a SCALAR_VALUE register, as long as it's value is 0. These statements make it difficult to reason about the type checking logic. Instead, skip more detailed type checking logic iff the register is 0, and the function expects a nullable type. This allows simplifying the type checking itself. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Check ARG_PTR_TO_SPINLOCK register type in check_func_argLorenz Bauer1-14/+14
Move the check for PTR_TO_MAP_VALUE to check_func_arg, where all other checking is done as well. Move the invocation of process_spin_lock away from the register type checking, to allow a future refactoring. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Set meta->raw_mode for pointers close to useLorenz Bauer1-1/+5
If we encounter a pointer to memory, we set meta->raw_mode depending on the type of memory we point at. What isn't obvious is that this information is only used when the next memory size argument is encountered. Move the assignment closer to where it's used, and add a comment that explains what is going on. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Make context access check genericLorenz Bauer1-3/+4
Always check context access if the register we're operating on is PTR_TO_CTX, rather than relying on ARG_PTR_TO_CTX. This allows simplifying the arg_type checking section of the function. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Make reference tracking genericLorenz Bauer1-16/+10
Instead of dealing with reg->ref_obj_id individually for every arg type that needs it, rely on the fact that ref_obj_id is zero if the register is not reference tracked. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Make BTF pointer type checking genericLorenz Bauer1-18/+20
Perform BTF type checks if the register we're working on contains a BTF pointer, rather than if the argument is for a BTF pointer. This is easier to understand, and allows removing the code from the arg_type checking section of the function. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Allow specifying a BTF ID per argument in function protosLorenz Bauer4-43/+27
Function prototypes using ARG_PTR_TO_BTF_ID currently use two ways to signal which BTF IDs are acceptable. First, bpf_func_proto.btf_id is an array of IDs, one for each argument. This array is only accessed up to the highest numbered argument that uses ARG_PTR_TO_BTF_ID and may therefore be less than five arguments long. It usually points at a BTF_ID_LIST. Second, check_btf_id is a function pointer that is called by the verifier if present. It gets the actual BTF ID of the register, and the argument number we're currently checking. It turns out that the only user check_arg_btf_id ignores the argument, and is simply used to check whether the BTF ID has a struct sock_common at it's start. Replace both of these mechanisms with an explicit BTF ID for each argument in a function proto. Thanks to btf_struct_ids_match this is very flexible: check_arg_btf_id can be replaced by requiring struct sock_common. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Check scalar or invalid register in check_helper_mem_accessLorenz Bauer1-13/+11
Move the check for a NULL or zero register to check_helper_mem_access. This makes check_stack_boundary easier to understand. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21btf: Make btf_set_contains take a const pointerLorenz Bauer1-1/+1
bsearch doesn't modify the contents of the array, so we can take a const pointer. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-21bpf: Fix sysfs export of empty BTF sectionTony Ambardar1-3/+3
If BTF data is missing or removed from the ELF section it is still exported via sysfs as a zero-length file: root@OpenWrt:/# ls -l /sys/kernel/btf/vmlinux -r--r--r-- 1 root root 0 Jul 18 02:59 /sys/kernel/btf/vmlinux Moreover, reads from this file succeed and leak kernel data: root@OpenWrt:/# hexdump -C /sys/kernel/btf/vmlinux|head -10 000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000cc0 00 00 00 00 00 00 00 00 00 00 00 00 80 83 b0 80 |................| 000cd0 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000ce0 00 00 00 00 00 00 00 00 00 00 00 00 57 ac 6e 9d |............W.n.| 000cf0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 002650 00 00 00 00 00 00 00 10 00 00 00 01 00 00 00 01 |................| 002660 80 82 9a c4 80 85 97 80 81 a9 51 68 00 00 00 02 |..........Qh....| 002670 80 25 44 dc 80 85 97 80 81 a9 50 24 81 ab c4 60 |.%D.......P$...`| This situation was first observed with kernel 5.4.x, cross-compiled for a MIPS target system. Fix by adding a sanity-check for export of zero-length data sections. Fixes: 341dfcf8d78e ("btf: expose BTF info through sysfs") Signed-off-by: Tony Ambardar <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Acked-by: John Fastabend <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/b38db205a66238f70823039a8c531535864eaac5.1600417359.git.Tony.Ambardar@gmail.com
2020-09-21bpf: Fix potential call bpf_link_free() in atomic contextMuchun Song1-6/+2
The in_atomic() macro cannot always detect atomic context, in particular, it cannot know about held spinlocks in non-preemptible kernels. Although, there is no user call bpf_link_put() with holding spinlock now, be on the safe side, so we can avoid this in the future. Signed-off-by: Muchun Song <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Acked-by: Song Liu <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-19bpf: Use hlist_add_head_rcu when linking to local_storageMartin KaFai Lau1-1/+1
The local_storage->list will be traversed by rcu reader in parallel. Thus, hlist_add_head_rcu() is needed in bpf_selem_link_storage_nolock(). This patch fixes it. This part of the code has recently been refactored in bpf-next and this patch makes changes to the new file "bpf_local_storage.c". Instead of using the original offending commit in the Fixes tag, the commit that created the file "bpf_local_storage.c" is used. A separate fix has been provided to the bpf tree. Fixes: 450af8d0f6be ("bpf: Split bpf_local_storage to bpf_sk_storage") Signed-off-by: Martin KaFai Lau <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Acked-by: Song Liu <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-17bpf: Add abnormal return checks.Alexei Starovoitov1-19/+48
LD_[ABS|IND] instructions may return from the function early. bpf_tail_call pseudo instruction is either fallthrough or return. Allow them in the subprograms only when subprograms are BTF annotated and have scalar return types. Allow ld_abs and tail_call in the main program even if it calls into subprograms. In the past that was not ok to do for ld_abs, since it was JITed with special exit sequence. Since bpf_gen_ld_abs() was introduced the ld_abs looks like normal exit insn from JIT point of view, so it's safe to allow them in the main program. Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-17bpf: allow for tailcalls in BPF subprograms for x64 JITMaciej Fijalkowski1-4/+17
Relax verifier's restriction that was meant to forbid tailcall usage when subprog count was higher than 1. Also, do not max out the stack depth of program that utilizes tailcalls. Signed-off-by: Maciej Fijalkowski <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-17bpf, x64: rework pro/epilogue and tailcall handling in JITMaciej Fijalkowski3-7/+51
This commit serves two things: 1) it optimizes BPF prologue/epilogue generation 2) it makes possible to have tailcalls within BPF subprogram Both points are related to each other since without 1), 2) could not be achieved. In [1], Alexei says: "The prologue will look like: nop5 xor eax,eax  // two new bytes if bpf_tail_call() is used in this // function push rbp mov rbp, rsp sub rsp, rounded_stack_depth push rax // zero init tail_call counter variable number of push rbx,r13,r14,r15 Then bpf_tail_call will pop variable number rbx,.. and final 'pop rax' Then 'add rsp, size_of_current_stack_frame' jmp to next function and skip over 'nop5; xor eax,eax; push rpb; mov rbp, rsp' This way new function will set its own stack size and will init tail call counter with whatever value the parent had. If next function doesn't use bpf_tail_call it won't have 'xor eax,eax'. Instead it would need to have 'nop2' in there." Implement that suggestion. Since the layout of stack is changed, tail call counter handling can not rely anymore on popping it to rbx just like it have been handled for constant prologue case and later overwrite of rbx with actual value of rbx pushed to stack. Therefore, let's use one of the register (%rcx) that is considered to be volatile/caller-saved and pop the value of tail call counter in there in the epilogue. Drop the BUILD_BUG_ON in emit_prologue and in emit_bpf_tail_call_indirect where instruction layout is not constant anymore. Introduce new poke target, 'tailcall_bypass' to poke descriptor that is dedicated for skipping the register pops and stack unwind that are generated right before the actual jump to target program. For case when the target program is not present, BPF program will skip the pop instructions and nop5 dedicated for jmpq $target. An example of such state when only R6 of callee saved registers is used by program: ffffffffc0513aa1: e9 0e 00 00 00 jmpq 0xffffffffc0513ab4 ffffffffc0513aa6: 5b pop %rbx ffffffffc0513aa7: 58 pop %rax ffffffffc0513aa8: 48 81 c4 00 00 00 00 add $0x0,%rsp ffffffffc0513aaf: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) ffffffffc0513ab4: 48 89 df mov %rbx,%rdi When target program is inserted, the jump that was there to skip pops/nop5 will become the nop5, so CPU will go over pops and do the actual tailcall. One might ask why there simply can not be pushes after the nop5? In the following example snippet: ffffffffc037030c: 48 89 fb mov %rdi,%rbx (...) ffffffffc0370332: 5b pop %rbx ffffffffc0370333: 58 pop %rax ffffffffc0370334: 48 81 c4 00 00 00 00 add $0x0,%rsp ffffffffc037033b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) ffffffffc0370340: 48 81 ec 00 00 00 00 sub $0x0,%rsp ffffffffc0370347: 50 push %rax ffffffffc0370348: 53 push %rbx ffffffffc0370349: 48 89 df mov %rbx,%rdi ffffffffc037034c: e8 f7 21 00 00 callq 0xffffffffc0372548 There is the bpf2bpf call (at ffffffffc037034c) right after the tailcall and jump target is not present. ctx is in %rbx register and BPF subprogram that we will call into on ffffffffc037034c is relying on it, e.g. it will pick ctx from there. Such code layout is therefore broken as we would overwrite the content of %rbx with the value that was pushed on the prologue. That is the reason for the 'bypass' approach. Special care needs to be taken during the install/update/remove of tailcall target. In case when target program is not present, the CPU must not execute the pop instructions that precede the tailcall. To address that, the following states can be defined: A nop, unwind, nop B nop, unwind, tail C skip, unwind, nop D skip, unwind, tail A is forbidden (lead to incorrectness). The state transitions between tailcall install/update/remove will work as follows: First install tail call f: C->D->B(f) * poke the tailcall, after that get rid of the skip Update tail call f to f': B(f)->B(f') * poke the tailcall (poke->tailcall_target) and do NOT touch the poke->tailcall_bypass Remove tail call: B(f')->C(f') * poke->tailcall_bypass is poked back to jump, then we wait the RCU grace period so that other programs will finish its execution and after that we are safe to remove the poke->tailcall_target Install new tail call (f''): C(f')->D(f'')->B(f''). * same as first step This way CPU can never be exposed to "unwind, tail" state. Last but not least, when tailcalls get mixed with bpf2bpf calls, it would be possible to encounter the endless loop due to clearing the tailcall counter if for example we would use the tailcall3-like from BPF selftests program that would be subprogram-based, meaning the tailcall would be present within the BPF subprogram. This test, broken down to particular steps, would do: entry -> set tailcall counter to 0, bump it by 1, tailcall to func0 func0 -> call subprog_tail (we are NOT skipping the first 11 bytes of prologue and this subprogram has a tailcall, therefore we clear the counter...) subprog -> do the same thing as entry and then loop forever. To address this, the idea is to go through the call chain of bpf2bpf progs and look for a tailcall presence throughout whole chain. If we saw a single tail call then each node in this call chain needs to be marked as a subprog that can reach the tailcall. We would later feed the JIT with this info and: - set eax to 0 only when tailcall is reachable and this is the entry prog - if tailcall is reachable but there's no tailcall in insns of currently JITed prog then push rax anyway, so that it will be possible to propagate further down the call chain - finally if tailcall is reachable, then we need to precede the 'call' insn with mov rax, [rbp - (stack_depth + 8)] Tail call related cases from test_verifier kselftest are also working fine. Sample BPF programs that utilize tail calls (sockex3, tracex5) work properly as well. [1]: https://lore.kernel.org/bpf/[email protected]/ Suggested-by: Alexei Starovoitov <[email protected]> Signed-off-by: Maciej Fijalkowski <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-17bpf: Limit caller's stack depth 256 for subprogs with tailcallsMaciej Fijalkowski1-0/+29
Protect against potential stack overflow that might happen when bpf2bpf calls get combined with tailcalls. Limit the caller's stack depth for such case down to 256 so that the worst case scenario would result in 8k stack size (32 which is tailcall limit * 256 = 8k). Suggested-by: Alexei Starovoitov <[email protected]> Signed-off-by: Maciej Fijalkowski <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-17bpf: rename poke descriptor's 'ip' member to 'tailcall_target'Maciej Fijalkowski2-9/+11
Reflect the actual purpose of poke->ip and rename it to poke->tailcall_target so that it will not the be confused with another poke target that will be introduced in next commit. While at it, do the same thing with poke->ip_stable - rename it to poke->tailcall_target_stable. Signed-off-by: Maciej Fijalkowski <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-17bpf: propagate poke descriptors to subprogramsMaciej Fijalkowski1-3/+63
Previously, there was no need for poke descriptors being present in subprogram's bpf_prog_aux struct since tailcalls were simply not allowed in them. Each subprog is JITed independently so in order to enable JITing subprograms that use tailcalls, do the following: - in fixup_bpf_calls() store the index of tailcall insn onto the generated poke descriptor, - in case when insn patching occurs, adjust the tailcall insn idx from bpf_patch_insn_data, - then in jit_subprogs() check whether the given poke descriptor belongs to the current subprog by checking if that previously stored absolute index of tail call insn is in the scope of the insns of given subprog, - update the insn->imm with new poke descriptor slot so that while JITing the proper poke descriptor will be grabbed This way each of the main program's poke descriptors are distributed across the subprograms poke descriptor array, so main program's descriptors can be untracked out of the prog array map. Add also subprog's aux struct to the BPF map poke_progs list by calling on it map_poke_track(). In case of any error, call the map_poke_untrack() on subprog's aux structs that have already been registered to prog array map. Signed-off-by: Maciej Fijalkowski <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]>
2020-09-15Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpfDavid S. Miller2-12/+7
Alexei Starovoitov says: ==================== pull-request: bpf 2020-09-15 The following pull-request contains BPF updates for your *net* tree. We've added 12 non-merge commits during the last 19 day(s) which contain a total of 10 files changed, 47 insertions(+), 38 deletions(-). The main changes are: 1) docs/bpf fixes, from Andrii. 2) ld_abs fix, from Daniel. 3) socket casting helpers fix, from Martin. 4) hash iterator fixes, from Yonghong. ==================== Signed-off-by: David S. Miller <[email protected]>
2020-09-15bpf: Add BPF_PROG_BIND_MAP syscallYiFei Zhu1-0/+63
This syscall binds a map to a program. Returns success if the map is already bound to the program. Signed-off-by: YiFei Zhu <[email protected]> Signed-off-by: Stanislav Fomichev <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Cc: YiFei Zhu <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-15bpf: Mutex protect used_maps array and countYiFei Zhu2-8/+23
To support modifying the used_maps array, we use a mutex to protect the use of the counter and the array. The mutex is initialized right after the prog aux is allocated, and destroyed right before prog aux is freed. This way we guarantee it's initialized for both cBPF and eBPF. Signed-off-by: YiFei Zhu <[email protected]> Signed-off-by: Stanislav Fomichev <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Cc: YiFei Zhu <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-15bpf: Fix a rcu warning for bpffs map pretty-printYonghong Song1-1/+3
Running selftest ./btf_btf -p the kernel had the following warning: [ 51.528185] WARNING: CPU: 3 PID: 1756 at kernel/bpf/hashtab.c:717 htab_map_get_next_key+0x2eb/0x300 [ 51.529217] Modules linked in: [ 51.529583] CPU: 3 PID: 1756 Comm: test_btf Not tainted 5.9.0-rc1+ #878 [ 51.530346] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.el7.centos 04/01/2014 [ 51.531410] RIP: 0010:htab_map_get_next_key+0x2eb/0x300 ... [ 51.542826] Call Trace: [ 51.543119] map_seq_next+0x53/0x80 [ 51.543528] seq_read+0x263/0x400 [ 51.543932] vfs_read+0xad/0x1c0 [ 51.544311] ksys_read+0x5f/0xe0 [ 51.544689] do_syscall_64+0x33/0x40 [ 51.545116] entry_SYSCALL_64_after_hwframe+0x44/0xa9 The related source code in kernel/bpf/hashtab.c: 709 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key) 710 { 711 struct bpf_htab *htab = container_of(map, struct bpf_htab, map); 712 struct hlist_nulls_head *head; 713 struct htab_elem *l, *next_l; 714 u32 hash, key_size; 715 int i = 0; 716 717 WARN_ON_ONCE(!rcu_read_lock_held()); In kernel/bpf/inode.c, bpffs map pretty print calls map->ops->map_get_next_key() without holding a rcu_read_lock(), hence causing the above warning. To fix the issue, just surrounding map->ops->map_get_next_key() with rcu read lock. Fixes: a26ca7c982cb ("bpf: btf: Add pretty print support to the basic arraymap") Reported-by: Alexei Starovoitov <[email protected]> Signed-off-by: Yonghong Song <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Cc: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-10objtool: Rename frame.h -> objtool.hJulien Thierry1-1/+1
Header frame.h is getting more code annotations to help objtool analyze object files. Rename the file to objtool.h. [ jpoimboe: add objtool.h to MAINTAINERS ] Signed-off-by: Julien Thierry <[email protected]> Signed-off-by: Josh Poimboeuf <[email protected]>
2020-09-08sysctl: Convert to iter interfacesMatthew Wilcox (Oracle)1-1/+1
Using the read_iter/write_iter interfaces allows for in-kernel users to set sysctls without using set_fs(). Also, the buffer is a string, so give it the real type of 'char *', not void *. [AV: Christoph's fixup folded in] Signed-off-by: Matthew Wilcox (Oracle) <[email protected]> Signed-off-by: Christoph Hellwig <[email protected]> Signed-off-by: Al Viro <[email protected]>
2020-09-08bpf: Permit map_ptr arithmetic with opcode add and offset 0Yonghong Song1-0/+4
Commit 41c48f3a98231 ("bpf: Support access to bpf map fields") added support to access map fields with CORE support. For example, struct bpf_map { __u32 max_entries; } __attribute__((preserve_access_index)); struct bpf_array { struct bpf_map map; __u32 elem_size; } __attribute__((preserve_access_index)); struct { __uint(type, BPF_MAP_TYPE_ARRAY); __uint(max_entries, 4); __type(key, __u32); __type(value, __u32); } m_array SEC(".maps"); SEC("cgroup_skb/egress") int cg_skb(void *ctx) { struct bpf_array *array = (struct bpf_array *)&m_array; /* .. array->map.max_entries .. */ } In kernel, bpf_htab has similar structure, struct bpf_htab { struct bpf_map map; ... } In the above cg_skb(), to access array->map.max_entries, with CORE, the clang will generate two builtin's. base = &m_array; /* access array.map */ map_addr = __builtin_preserve_struct_access_info(base, 0, 0); /* access array.map.max_entries */ max_entries_addr = __builtin_preserve_struct_access_info(map_addr, 0, 0); max_entries = *max_entries_addr; In the current llvm, if two builtin's are in the same function or in the same function after inlining, the compiler is smart enough to chain them together and generates like below: base = &m_array; max_entries = *(base + reloc_offset); /* reloc_offset = 0 in this case */ and we are fine. But if we force no inlining for one of functions in test_map_ptr() selftest, e.g., check_default(), the above two __builtin_preserve_* will be in two different functions. In this case, we will have code like: func check_hash(): reloc_offset_map = 0; base = &m_array; map_base = base + reloc_offset_map; check_default(map_base, ...) func check_default(map_base, ...): max_entries = *(map_base + reloc_offset_max_entries); In kernel, map_ptr (CONST_PTR_TO_MAP) does not allow any arithmetic. The above "map_base = base + reloc_offset_map" will trigger a verifier failure. ; VERIFY(check_default(&hash->map, map)); 0: (18) r7 = 0xffffb4fe8018a004 2: (b4) w1 = 110 3: (63) *(u32 *)(r7 +0) = r1 R1_w=invP110 R7_w=map_value(id=0,off=4,ks=4,vs=8,imm=0) R10=fp0 ; VERIFY_TYPE(BPF_MAP_TYPE_HASH, check_hash); 4: (18) r1 = 0xffffb4fe8018a000 6: (b4) w2 = 1 7: (63) *(u32 *)(r1 +0) = r2 R1_w=map_value(id=0,off=0,ks=4,vs=8,imm=0) R2_w=invP1 R7_w=map_value(id=0,off=4,ks=4,vs=8,imm=0) R10=fp0 8: (b7) r2 = 0 9: (18) r8 = 0xffff90bcb500c000 11: (18) r1 = 0xffff90bcb500c000 13: (0f) r1 += r2 R1 pointer arithmetic on map_ptr prohibited To fix the issue, let us permit map_ptr + 0 arithmetic which will result in exactly the same map_ptr. Signed-off-by: Yonghong Song <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
2020-09-04Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski4-6/+6
We got slightly different patches removing a double word in a comment in net/ipv4/raw.c - picked the version from net. Simple conflict in drivers/net/ethernet/ibm/ibmvnic.c. Use cached values instead of VNIC login response buffer (following what commit 507ebe6444a4 ("ibmvnic: Fix use-after-free of VNIC login response buffer") did). Signed-off-by: Jakub Kicinski <[email protected]>
2020-09-03Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netLinus Torvalds1-1/+1
Pull networking fixes from David Miller: 1) Use netif_rx_ni() when necessary in batman-adv stack, from Jussi Kivilinna. 2) Fix loss of RTT samples in rxrpc, from David Howells. 3) Memory leak in hns_nic_dev_probe(), from Dignhao Liu. 4) ravb module cannot be unloaded, fix from Yuusuke Ashizuka. 5) We disable BH for too lokng in sctp_get_port_local(), add a cond_resched() here as well, from Xin Long. 6) Fix memory leak in st95hf_in_send_cmd, from Dinghao Liu. 7) Out of bound access in bpf_raw_tp_link_fill_link_info(), from Yonghong Song. 8) Missing of_node_put() in mt7530 DSA driver, from Sumera Priyadarsini. 9) Fix crash in bnxt_fw_reset_task(), from Michael Chan. 10) Fix geneve tunnel checksumming bug in hns3, from Yi Li. 11) Memory leak in rxkad_verify_response, from Dinghao Liu. 12) In tipc, don't use smp_processor_id() in preemptible context. From Tuong Lien. 13) Fix signedness issue in mlx4 memory allocation, from Shung-Hsi Yu. 14) Missing clk_disable_prepare() in gemini driver, from Dan Carpenter. 15) Fix ABI mismatch between driver and firmware in nfp, from Louis Peens. * git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (110 commits) net/smc: fix sock refcounting in case of termination net/smc: reset sndbuf_desc if freed net/smc: set rx_off for SMCR explicitly net/smc: fix toleration of fake add_link messages tg3: Fix soft lockup when tg3_reset_task() fails. doc: net: dsa: Fix typo in config code sample net: dp83867: Fix WoL SecureOn password nfp: flower: fix ABI mismatch between driver and firmware tipc: fix shutdown() of connectionless socket ipv6: Fix sysctl max for fib_multipath_hash_policy drivers/net/wan/hdlc: Change the default of hard_header_len to 0 net: gemini: Fix another missing clk_disable_unprepare() in probe net: bcmgenet: fix mask check in bcmgenet_validate_flow() amd-xgbe: Add support for new port mode net: usb: dm9601: Add USB ID of Keenetic Plus DSL vhost: fix typo in error message net: ethernet: mlx4: Fix memory allocation in mlx4_buddy_init() pktgen: fix error message with wrong function name net: ethernet: ti: am65-cpsw: fix rmii 100Mbit link mode cxgb4: fix thermal zone device registration ...
2020-09-03bpf: Do not use bucket_lock for hashmap iteratorYonghong Song1-11/+4
Currently, for hashmap, the bpf iterator will grab a bucket lock, a spinlock, before traversing the elements in the bucket. This can ensure all bpf visted elements are valid. But this mechanism may cause deadlock if update/deletion happens to the same bucket of the visited map in the program. For example, if we added bpf_map_update_elem() call to the same visited element in selftests bpf_iter_bpf_hash_map.c, we will have the following deadlock: ============================================ WARNING: possible recursive locking detected 5.9.0-rc1+ #841 Not tainted -------------------------------------------- test_progs/1750 is trying to acquire lock: ffff9a5bb73c5e70 (&htab->buckets[i].raw_lock){....}-{2:2}, at: htab_map_update_elem+0x1cf/0x410 but task is already holding lock: ffff9a5bb73c5e20 (&htab->buckets[i].raw_lock){....}-{2:2}, at: bpf_hash_map_seq_find_next+0x94/0x120 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&htab->buckets[i].raw_lock); lock(&htab->buckets[i].raw_lock); *** DEADLOCK *** ... Call Trace: dump_stack+0x78/0xa0 __lock_acquire.cold.74+0x209/0x2e3 lock_acquire+0xba/0x380 ? htab_map_update_elem+0x1cf/0x410 ? __lock_acquire+0x639/0x20c0 _raw_spin_lock_irqsave+0x3b/0x80 ? htab_map_update_elem+0x1cf/0x410 htab_map_update_elem+0x1cf/0x410 ? lock_acquire+0xba/0x380 bpf_prog_ad6dab10433b135d_dump_bpf_hash_map+0x88/0xa9c ? find_held_lock+0x34/0xa0 bpf_iter_run_prog+0x81/0x16e __bpf_hash_map_seq_show+0x145/0x180 bpf_seq_read+0xff/0x3d0 vfs_read+0xad/0x1c0 ksys_read+0x5f/0xe0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ... The bucket_lock first grabbed in seq_ops->next() called by bpf_seq_read(), and then grabbed again in htab_map_update_elem() in the bpf program, causing deadlocks. Actually, we do not need bucket_lock here, we can just use rcu_read_lock() similar to netlink iterator where the rcu_read_{lock,unlock} likes below: seq_ops->start(): rcu_read_lock(); seq_ops->next(): rcu_read_unlock(); /* next element */ rcu_read_lock(); seq_ops->stop(); rcu_read_unlock(); Compared to old bucket_lock mechanism, if concurrent updata/delete happens, we may visit stale elements, miss some elements, or repeat some elements. I think this is a reasonable compromise. For users wanting to avoid stale, missing/repeated accesses, bpf_map batch access syscall interface can be used. Signed-off-by: Yonghong Song <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
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