From 1e0bd5a091e5d9e0f1d5b0e6329b87bb1792f784 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sun, 17 Nov 2019 09:28:02 -0800 Subject: bpf: Switch bpf_map ref counter to atomic64_t so bpf_map_inc() never fails 92117d8443bc ("bpf: fix refcnt overflow") turned refcounting of bpf_map into potentially failing operation, when refcount reaches BPF_MAX_REFCNT limit (32k). Due to using 32-bit counter, it's possible in practice to overflow refcounter and make it wrap around to 0, causing erroneous map free, while there are still references to it, causing use-after-free problems. But having a failing refcounting operations are problematic in some cases. One example is mmap() interface. After establishing initial memory-mapping, user is allowed to arbitrarily map/remap/unmap parts of mapped memory, arbitrarily splitting it into multiple non-contiguous regions. All this happening without any control from the users of mmap subsystem. Rather mmap subsystem sends notifications to original creator of memory mapping through open/close callbacks, which are optionally specified during initial memory mapping creation. These callbacks are used to maintain accurate refcount for bpf_map (see next patch in this series). The problem is that open() callback is not supposed to fail, because memory-mapped resource is set up and properly referenced. This is posing a problem for using memory-mapping with BPF maps. One solution to this is to maintain separate refcount for just memory-mappings and do single bpf_map_inc/bpf_map_put when it goes from/to zero, respectively. There are similar use cases in current work on tcp-bpf, necessitating extra counter as well. This seems like a rather unfortunate and ugly solution that doesn't scale well to various new use cases. Another approach to solve this is to use non-failing refcount_t type, which uses 32-bit counter internally, but, once reaching overflow state at UINT_MAX, stays there. This utlimately causes memory leak, but prevents use after free. But given refcounting is not the most performance-critical operation with BPF maps (it's not used from running BPF program code), we can also just switch to 64-bit counter that can't overflow in practice, potentially disadvantaging 32-bit platforms a tiny bit. This simplifies semantics and allows above described scenarios to not worry about failing refcount increment operation. In terms of struct bpf_map size, we are still good and use the same amount of space: BEFORE (3 cache lines, 8 bytes of padding at the end): struct bpf_map { const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */ struct bpf_map * inner_map_meta; /* 8 8 */ void * security; /* 16 8 */ enum bpf_map_type map_type; /* 24 4 */ u32 key_size; /* 28 4 */ u32 value_size; /* 32 4 */ u32 max_entries; /* 36 4 */ u32 map_flags; /* 40 4 */ int spin_lock_off; /* 44 4 */ u32 id; /* 48 4 */ int numa_node; /* 52 4 */ u32 btf_key_type_id; /* 56 4 */ u32 btf_value_type_id; /* 60 4 */ /* --- cacheline 1 boundary (64 bytes) --- */ struct btf * btf; /* 64 8 */ struct bpf_map_memory memory; /* 72 16 */ bool unpriv_array; /* 88 1 */ bool frozen; /* 89 1 */ /* XXX 38 bytes hole, try to pack */ /* --- cacheline 2 boundary (128 bytes) --- */ atomic_t refcnt __attribute__((__aligned__(64))); /* 128 4 */ atomic_t usercnt; /* 132 4 */ struct work_struct work; /* 136 32 */ char name[16]; /* 168 16 */ /* size: 192, cachelines: 3, members: 21 */ /* sum members: 146, holes: 1, sum holes: 38 */ /* padding: 8 */ /* forced alignments: 2, forced holes: 1, sum forced holes: 38 */ } __attribute__((__aligned__(64))); AFTER (same 3 cache lines, no extra padding now): struct bpf_map { const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */ struct bpf_map * inner_map_meta; /* 8 8 */ void * security; /* 16 8 */ enum bpf_map_type map_type; /* 24 4 */ u32 key_size; /* 28 4 */ u32 value_size; /* 32 4 */ u32 max_entries; /* 36 4 */ u32 map_flags; /* 40 4 */ int spin_lock_off; /* 44 4 */ u32 id; /* 48 4 */ int numa_node; /* 52 4 */ u32 btf_key_type_id; /* 56 4 */ u32 btf_value_type_id; /* 60 4 */ /* --- cacheline 1 boundary (64 bytes) --- */ struct btf * btf; /* 64 8 */ struct bpf_map_memory memory; /* 72 16 */ bool unpriv_array; /* 88 1 */ bool frozen; /* 89 1 */ /* XXX 38 bytes hole, try to pack */ /* --- cacheline 2 boundary (128 bytes) --- */ atomic64_t refcnt __attribute__((__aligned__(64))); /* 128 8 */ atomic64_t usercnt; /* 136 8 */ struct work_struct work; /* 144 32 */ char name[16]; /* 176 16 */ /* size: 192, cachelines: 3, members: 21 */ /* sum members: 154, holes: 1, sum holes: 38 */ /* forced alignments: 2, forced holes: 1, sum forced holes: 38 */ } __attribute__((__aligned__(64))); This patch, while modifying all users of bpf_map_inc, also cleans up its interface to match bpf_map_put with separate operations for bpf_map_inc and bpf_map_inc_with_uref (to match bpf_map_put and bpf_map_put_with_uref, respectively). Also, given there are no users of bpf_map_inc_not_zero specifying uref=true, remove uref flag and default to uref=false internally. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20191117172806.2195367-2-andriin@fb.com --- include/linux/bpf.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'include/linux') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 5b81cde47314..34a34445c009 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -103,8 +103,8 @@ struct bpf_map { /* The 3rd and 4th cacheline with misc members to avoid false sharing * particularly with refcounting. */ - atomic_t refcnt ____cacheline_aligned; - atomic_t usercnt; + atomic64_t refcnt ____cacheline_aligned; + atomic64_t usercnt; struct work_struct work; char name[BPF_OBJ_NAME_LEN]; }; @@ -783,9 +783,9 @@ void bpf_map_free_id(struct bpf_map *map, bool do_idr_lock); struct bpf_map *bpf_map_get_with_uref(u32 ufd); struct bpf_map *__bpf_map_get(struct fd f); -struct bpf_map * __must_check bpf_map_inc(struct bpf_map *map, bool uref); -struct bpf_map * __must_check bpf_map_inc_not_zero(struct bpf_map *map, - bool uref); +void bpf_map_inc(struct bpf_map *map); +void bpf_map_inc_with_uref(struct bpf_map *map); +struct bpf_map * __must_check bpf_map_inc_not_zero(struct bpf_map *map); void bpf_map_put_with_uref(struct bpf_map *map); void bpf_map_put(struct bpf_map *map); int bpf_map_charge_memlock(struct bpf_map *map, u32 pages); -- cgit From 85192dbf4de08795afe2b88e52a36fc6abfc3dba Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sun, 17 Nov 2019 09:28:03 -0800 Subject: bpf: Convert bpf_prog refcnt to atomic64_t Similarly to bpf_map's refcnt/usercnt, convert bpf_prog's refcnt to atomic64 and remove artificial 32k limit. This allows to make bpf_prog's refcounting non-failing, simplifying logic of users of bpf_prog_add/bpf_prog_inc. Validated compilation by running allyesconfig kernel build. Suggested-by: Daniel Borkmann Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20191117172806.2195367-3-andriin@fb.com --- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 9 ++----- drivers/net/ethernet/cavium/thunder/nicvf_main.c | 9 ++----- drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 7 ++---- drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 24 +++++------------- drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 18 ++++---------- drivers/net/ethernet/qlogic/qede/qede_main.c | 8 ++---- drivers/net/virtio_net.c | 7 ++---- include/linux/bpf.h | 13 ++++------ kernel/bpf/inode.c | 5 ++-- kernel/bpf/syscall.c | 30 +++++++---------------- kernel/events/core.c | 7 ++---- 11 files changed, 40 insertions(+), 97 deletions(-) (limited to 'include/linux') diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c index c07172429c70..9da4fbee3cf7 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c @@ -3171,13 +3171,8 @@ static int bnxt_init_one_rx_ring(struct bnxt *bp, int ring_nr) bnxt_init_rxbd_pages(ring, type); if (BNXT_RX_PAGE_MODE(bp) && bp->xdp_prog) { - rxr->xdp_prog = bpf_prog_add(bp->xdp_prog, 1); - if (IS_ERR(rxr->xdp_prog)) { - int rc = PTR_ERR(rxr->xdp_prog); - - rxr->xdp_prog = NULL; - return rc; - } + bpf_prog_add(bp->xdp_prog, 1); + rxr->xdp_prog = bp->xdp_prog; } prod = rxr->rx_prod; for (i = 0; i < bp->rx_ring_size; i++) { diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c index 40a44dcb3d9b..f28409279ea4 100644 --- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c +++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c @@ -1876,13 +1876,8 @@ static int nicvf_xdp_setup(struct nicvf *nic, struct bpf_prog *prog) if (nic->xdp_prog) { /* Attach BPF program */ - nic->xdp_prog = bpf_prog_add(nic->xdp_prog, nic->rx_queues - 1); - if (!IS_ERR(nic->xdp_prog)) { - bpf_attached = true; - } else { - ret = PTR_ERR(nic->xdp_prog); - nic->xdp_prog = NULL; - } + bpf_prog_add(nic->xdp_prog, nic->rx_queues - 1); + bpf_attached = true; } /* Calculate Tx queues needed for XDP and network stack */ diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c index c26c0a7cbb6b..acc56606d3a5 100644 --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c @@ -1807,11 +1807,8 @@ static int setup_xdp(struct net_device *dev, struct bpf_prog *prog) if (prog && !xdp_mtu_valid(priv, dev->mtu)) return -EINVAL; - if (prog) { - prog = bpf_prog_add(prog, priv->num_channels); - if (IS_ERR(prog)) - return PTR_ERR(prog); - } + if (prog) + bpf_prog_add(prog, priv->num_channels); up = netif_running(dev); need_update = (!!priv->xdp_prog != !!prog); diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c index 40ec5acf79c0..d4697beeacc2 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c @@ -2286,11 +2286,7 @@ int mlx4_en_try_alloc_resources(struct mlx4_en_priv *priv, lockdep_is_held(&priv->mdev->state_lock)); if (xdp_prog && carry_xdp_prog) { - xdp_prog = bpf_prog_add(xdp_prog, tmp->rx_ring_num); - if (IS_ERR(xdp_prog)) { - mlx4_en_free_resources(tmp); - return PTR_ERR(xdp_prog); - } + bpf_prog_add(xdp_prog, tmp->rx_ring_num); for (i = 0; i < tmp->rx_ring_num; i++) rcu_assign_pointer(tmp->rx_ring[i]->xdp_prog, xdp_prog); @@ -2782,11 +2778,9 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) * program for a new one. */ if (priv->tx_ring_num[TX_XDP] == xdp_ring_num) { - if (prog) { - prog = bpf_prog_add(prog, priv->rx_ring_num - 1); - if (IS_ERR(prog)) - return PTR_ERR(prog); - } + if (prog) + bpf_prog_add(prog, priv->rx_ring_num - 1); + mutex_lock(&mdev->state_lock); for (i = 0; i < priv->rx_ring_num; i++) { old_prog = rcu_dereference_protected( @@ -2807,13 +2801,8 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) if (!tmp) return -ENOMEM; - if (prog) { - prog = bpf_prog_add(prog, priv->rx_ring_num - 1); - if (IS_ERR(prog)) { - err = PTR_ERR(prog); - goto out; - } - } + if (prog) + bpf_prog_add(prog, priv->rx_ring_num - 1); mutex_lock(&mdev->state_lock); memcpy(&new_prof, priv->prof, sizeof(struct mlx4_en_port_profile)); @@ -2862,7 +2851,6 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) unlock_out: mutex_unlock(&mdev->state_lock); -out: kfree(tmp); return err; } diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c index 772bfdbdeb9c..1d4a66fb466a 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c @@ -408,12 +408,9 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c, rq->stats = &c->priv->channel_stats[c->ix].rq; INIT_WORK(&rq->recover_work, mlx5e_rq_err_cqe_work); - rq->xdp_prog = params->xdp_prog ? bpf_prog_inc(params->xdp_prog) : NULL; - if (IS_ERR(rq->xdp_prog)) { - err = PTR_ERR(rq->xdp_prog); - rq->xdp_prog = NULL; - goto err_rq_wq_destroy; - } + if (params->xdp_prog) + bpf_prog_inc(params->xdp_prog); + rq->xdp_prog = params->xdp_prog; rq_xdp_ix = rq->ix; if (xsk) @@ -4406,16 +4403,11 @@ static int mlx5e_xdp_set(struct net_device *netdev, struct bpf_prog *prog) /* no need for full reset when exchanging programs */ reset = (!priv->channels.params.xdp_prog || !prog); - if (was_opened && !reset) { + if (was_opened && !reset) /* num_channels is invariant here, so we can take the * batched reference right upfront. */ - prog = bpf_prog_add(prog, priv->channels.num); - if (IS_ERR(prog)) { - err = PTR_ERR(prog); - goto unlock; - } - } + bpf_prog_add(prog, priv->channels.num); if (was_opened && reset) { struct mlx5e_channels new_channels = {}; diff --git a/drivers/net/ethernet/qlogic/qede/qede_main.c b/drivers/net/ethernet/qlogic/qede/qede_main.c index 8d1c208f778f..1e26964fe4e9 100644 --- a/drivers/net/ethernet/qlogic/qede/qede_main.c +++ b/drivers/net/ethernet/qlogic/qede/qede_main.c @@ -2107,12 +2107,8 @@ static int qede_start_queues(struct qede_dev *edev, bool clear_stats) if (rc) goto out; - fp->rxq->xdp_prog = bpf_prog_add(edev->xdp_prog, 1); - if (IS_ERR(fp->rxq->xdp_prog)) { - rc = PTR_ERR(fp->rxq->xdp_prog); - fp->rxq->xdp_prog = NULL; - goto out; - } + bpf_prog_add(edev->xdp_prog, 1); + fp->rxq->xdp_prog = edev->xdp_prog; } if (fp->type & QEDE_FASTPATH_TX) { diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 5a635f028bdc..4d7d5434cc5d 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -2445,11 +2445,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, if (!prog && !old_prog) return 0; - if (prog) { - prog = bpf_prog_add(prog, vi->max_queue_pairs - 1); - if (IS_ERR(prog)) - return PTR_ERR(prog); - } + if (prog) + bpf_prog_add(prog, vi->max_queue_pairs - 1); /* Make sure NAPI is not using any XDP TX queues for RX. */ if (netif_running(dev)) { diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 34a34445c009..fb606dc61a3a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -485,7 +485,7 @@ struct bpf_func_info_aux { }; struct bpf_prog_aux { - atomic_t refcnt; + atomic64_t refcnt; u32 used_map_cnt; u32 max_ctx_offset; u32 max_pkt_offset; @@ -770,9 +770,9 @@ extern const struct bpf_verifier_ops xdp_analyzer_ops; struct bpf_prog *bpf_prog_get(u32 ufd); struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, enum bpf_prog_type type, bool attach_drv); -struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog, int i); +void bpf_prog_add(struct bpf_prog *prog, int i); void bpf_prog_sub(struct bpf_prog *prog, int i); -struct bpf_prog * __must_check bpf_prog_inc(struct bpf_prog *prog); +void bpf_prog_inc(struct bpf_prog *prog); struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog); void bpf_prog_put(struct bpf_prog *prog); int __bpf_prog_charge(struct user_struct *user, u32 pages); @@ -912,10 +912,8 @@ static inline struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, return ERR_PTR(-EOPNOTSUPP); } -static inline struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog, - int i) +static inline void bpf_prog_add(struct bpf_prog *prog, int i) { - return ERR_PTR(-EOPNOTSUPP); } static inline void bpf_prog_sub(struct bpf_prog *prog, int i) @@ -926,9 +924,8 @@ static inline void bpf_prog_put(struct bpf_prog *prog) { } -static inline struct bpf_prog * __must_check bpf_prog_inc(struct bpf_prog *prog) +static inline void bpf_prog_inc(struct bpf_prog *prog) { - return ERR_PTR(-EOPNOTSUPP); } static inline struct bpf_prog *__must_check diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index 2f17f24258dc..ecf42bec38c0 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -31,7 +31,7 @@ static void *bpf_any_get(void *raw, enum bpf_type type) { switch (type) { case BPF_TYPE_PROG: - raw = bpf_prog_inc(raw); + bpf_prog_inc(raw); break; case BPF_TYPE_MAP: bpf_map_inc_with_uref(raw); @@ -534,7 +534,8 @@ static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type if (!bpf_prog_get_ok(prog, &type, false)) return ERR_PTR(-EINVAL); - return bpf_prog_inc(prog); + bpf_prog_inc(prog); + return prog; } struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 20030751b7a2..52fe4bacb330 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1339,7 +1339,7 @@ static void __bpf_prog_put_noref(struct bpf_prog *prog, bool deferred) static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock) { - if (atomic_dec_and_test(&prog->aux->refcnt)) { + if (atomic64_dec_and_test(&prog->aux->refcnt)) { perf_event_bpf_event(prog, PERF_BPF_EVENT_PROG_UNLOAD, 0); /* bpf_prog_free_id() must be called first */ bpf_prog_free_id(prog, do_idr_lock); @@ -1445,16 +1445,9 @@ static struct bpf_prog *____bpf_prog_get(struct fd f) return f.file->private_data; } -/* prog's refcnt limit */ -#define BPF_MAX_REFCNT 32768 - -struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i) +void bpf_prog_add(struct bpf_prog *prog, int i) { - if (atomic_add_return(i, &prog->aux->refcnt) > BPF_MAX_REFCNT) { - atomic_sub(i, &prog->aux->refcnt); - return ERR_PTR(-EBUSY); - } - return prog; + atomic64_add(i, &prog->aux->refcnt); } EXPORT_SYMBOL_GPL(bpf_prog_add); @@ -1465,13 +1458,13 @@ void bpf_prog_sub(struct bpf_prog *prog, int i) * path holds a reference to the program, thus atomic_sub() can * be safely used in such cases! */ - WARN_ON(atomic_sub_return(i, &prog->aux->refcnt) == 0); + WARN_ON(atomic64_sub_return(i, &prog->aux->refcnt) == 0); } EXPORT_SYMBOL_GPL(bpf_prog_sub); -struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog) +void bpf_prog_inc(struct bpf_prog *prog) { - return bpf_prog_add(prog, 1); + atomic64_inc(&prog->aux->refcnt); } EXPORT_SYMBOL_GPL(bpf_prog_inc); @@ -1480,12 +1473,7 @@ struct bpf_prog *bpf_prog_inc_not_zero(struct bpf_prog *prog) { int refold; - refold = atomic_fetch_add_unless(&prog->aux->refcnt, 1, 0); - - if (refold >= BPF_MAX_REFCNT) { - __bpf_prog_put(prog, false); - return ERR_PTR(-EBUSY); - } + refold = atomic64_fetch_add_unless(&prog->aux->refcnt, 1, 0); if (!refold) return ERR_PTR(-ENOENT); @@ -1523,7 +1511,7 @@ static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *attach_type, goto out; } - prog = bpf_prog_inc(prog); + bpf_prog_inc(prog); out: fdput(f); return prog; @@ -1714,7 +1702,7 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr) prog->orig_prog = NULL; prog->jited = 0; - atomic_set(&prog->aux->refcnt, 1); + atomic64_set(&prog->aux->refcnt, 1); prog->gpl_compatible = is_gpl ? 1 : 0; if (bpf_prog_is_dev_bound(prog->aux)) { diff --git a/kernel/events/core.c b/kernel/events/core.c index aec8dba2bea4..73c616876597 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10477,12 +10477,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, context = parent_event->overflow_handler_context; #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_EVENT_TRACING) if (overflow_handler == bpf_overflow_handler) { - struct bpf_prog *prog = bpf_prog_inc(parent_event->prog); + struct bpf_prog *prog = parent_event->prog; - if (IS_ERR(prog)) { - err = PTR_ERR(prog); - goto err_ns; - } + bpf_prog_inc(prog); event->prog = prog; event->orig_overflow_handler = parent_event->orig_overflow_handler; -- cgit From fc9702273e2edb90400a34b3be76f7b08fa3344b Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sun, 17 Nov 2019 09:28:04 -0800 Subject: bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY Add ability to memory-map contents of BPF array map. This is extremely useful for working with BPF global data from userspace programs. It allows to avoid typical bpf_map_{lookup,update}_elem operations, improving both performance and usability. There had to be special considerations for map freezing, to avoid having writable memory view into a frozen map. To solve this issue, map freezing and mmap-ing is happening under mutex now: - if map is already frozen, no writable mapping is allowed; - if map has writable memory mappings active (accounted in map->writecnt), map freezing will keep failing with -EBUSY; - once number of writable memory mappings drops to zero, map freezing can be performed again. Only non-per-CPU plain arrays are supported right now. Maps with spinlocks can't be memory mapped either. For BPF_F_MMAPABLE array, memory allocation has to be done through vmalloc() to be mmap()'able. We also need to make sure that array data memory is page-sized and page-aligned, so we over-allocate memory in such a way that struct bpf_array is at the end of a single page of memory with array->value being aligned with the start of the second page. On deallocation we need to accomodate this memory arrangement to free vmalloc()'ed memory correctly. One important consideration regarding how memory-mapping subsystem functions. Memory-mapping subsystem provides few optional callbacks, among them open() and close(). close() is called for each memory region that is unmapped, so that users can decrease their reference counters and free up resources, if necessary. open() is *almost* symmetrical: it's called for each memory region that is being mapped, **except** the very first one. So bpf_map_mmap does initial refcnt bump, while open() will do any extra ones after that. Thus number of close() calls is equal to number of open() calls plus one more. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Song Liu Acked-by: John Fastabend Acked-by: Johannes Weiner Link: https://lore.kernel.org/bpf/20191117172806.2195367-4-andriin@fb.com --- include/linux/bpf.h | 11 +++-- include/linux/vmalloc.h | 1 + include/uapi/linux/bpf.h | 3 ++ kernel/bpf/arraymap.c | 58 ++++++++++++++++++++++--- kernel/bpf/syscall.c | 99 ++++++++++++++++++++++++++++++++++++++++-- mm/vmalloc.c | 20 +++++++++ tools/include/uapi/linux/bpf.h | 3 ++ 7 files changed, 183 insertions(+), 12 deletions(-) (limited to 'include/linux') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index fb606dc61a3a..e913dd5946ae 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -68,6 +69,7 @@ struct bpf_map_ops { u64 *imm, u32 off); int (*map_direct_value_meta)(const struct bpf_map *map, u64 imm, u32 *off); + int (*map_mmap)(struct bpf_map *map, struct vm_area_struct *vma); }; struct bpf_map_memory { @@ -96,9 +98,10 @@ struct bpf_map { u32 btf_value_type_id; struct btf *btf; struct bpf_map_memory memory; + char name[BPF_OBJ_NAME_LEN]; bool unpriv_array; - bool frozen; /* write-once */ - /* 48 bytes hole */ + bool frozen; /* write-once; write-protected by freeze_mutex */ + /* 22 bytes hole */ /* The 3rd and 4th cacheline with misc members to avoid false sharing * particularly with refcounting. @@ -106,7 +109,8 @@ struct bpf_map { atomic64_t refcnt ____cacheline_aligned; atomic64_t usercnt; struct work_struct work; - char name[BPF_OBJ_NAME_LEN]; + struct mutex freeze_mutex; + u64 writecnt; /* writable mmap cnt; protected by freeze_mutex */ }; static inline bool map_value_has_spin_lock(const struct bpf_map *map) @@ -795,6 +799,7 @@ void bpf_map_charge_finish(struct bpf_map_memory *mem); void bpf_map_charge_move(struct bpf_map_memory *dst, struct bpf_map_memory *src); void *bpf_map_area_alloc(size_t size, int numa_node); +void *bpf_map_area_mmapable_alloc(size_t size, int numa_node); void bpf_map_area_free(void *base); void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr); diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 4e7809408073..b4c58a191eb1 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -93,6 +93,7 @@ extern void *vzalloc(unsigned long size); extern void *vmalloc_user(unsigned long size); extern void *vmalloc_node(unsigned long size, int node); extern void *vzalloc_node(unsigned long size, int node); +extern void *vmalloc_user_node_flags(unsigned long size, int node, gfp_t flags); extern void *vmalloc_exec(unsigned long size); extern void *vmalloc_32(unsigned long size); extern void *vmalloc_32_user(unsigned long size); diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 4842a134b202..dbbcf0b02970 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -348,6 +348,9 @@ enum bpf_attach_type { /* Clone map from listener for newly accepted socket */ #define BPF_F_CLONE (1U << 9) +/* Enable memory-mapping BPF map */ +#define BPF_F_MMAPABLE (1U << 10) + /* flags for BPF_PROG_QUERY */ #define BPF_F_QUERY_EFFECTIVE (1U << 0) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 1c65ce0098a9..a42097c36b0c 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -14,7 +14,7 @@ #include "map_in_map.h" #define ARRAY_CREATE_FLAG_MASK \ - (BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK) + (BPF_F_NUMA_NODE | BPF_F_MMAPABLE | BPF_F_ACCESS_MASK) static void bpf_array_free_percpu(struct bpf_array *array) { @@ -59,6 +59,10 @@ int array_map_alloc_check(union bpf_attr *attr) (percpu && numa_node != NUMA_NO_NODE)) return -EINVAL; + if (attr->map_type != BPF_MAP_TYPE_ARRAY && + attr->map_flags & BPF_F_MMAPABLE) + return -EINVAL; + if (attr->value_size > KMALLOC_MAX_SIZE) /* if value_size is bigger, the user space won't be able to * access the elements. @@ -102,10 +106,19 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) } array_size = sizeof(*array); - if (percpu) + if (percpu) { array_size += (u64) max_entries * sizeof(void *); - else - array_size += (u64) max_entries * elem_size; + } else { + /* rely on vmalloc() to return page-aligned memory and + * ensure array->value is exactly page-aligned + */ + if (attr->map_flags & BPF_F_MMAPABLE) { + array_size = PAGE_ALIGN(array_size); + array_size += PAGE_ALIGN((u64) max_entries * elem_size); + } else { + array_size += (u64) max_entries * elem_size; + } + } /* make sure there is no u32 overflow later in round_up() */ cost = array_size; @@ -117,7 +130,20 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) return ERR_PTR(ret); /* allocate all map elements and zero-initialize them */ - array = bpf_map_area_alloc(array_size, numa_node); + if (attr->map_flags & BPF_F_MMAPABLE) { + void *data; + + /* kmalloc'ed memory can't be mmap'ed, use explicit vmalloc */ + data = bpf_map_area_mmapable_alloc(array_size, numa_node); + if (!data) { + bpf_map_charge_finish(&mem); + return ERR_PTR(-ENOMEM); + } + array = data + PAGE_ALIGN(sizeof(struct bpf_array)) + - offsetof(struct bpf_array, value); + } else { + array = bpf_map_area_alloc(array_size, numa_node); + } if (!array) { bpf_map_charge_finish(&mem); return ERR_PTR(-ENOMEM); @@ -350,6 +376,11 @@ static int array_map_delete_elem(struct bpf_map *map, void *key) return -EINVAL; } +static void *array_map_vmalloc_addr(struct bpf_array *array) +{ + return (void *)round_down((unsigned long)array, PAGE_SIZE); +} + /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ static void array_map_free(struct bpf_map *map) { @@ -365,7 +396,10 @@ static void array_map_free(struct bpf_map *map) if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY) bpf_array_free_percpu(array); - bpf_map_area_free(array); + if (array->map.map_flags & BPF_F_MMAPABLE) + bpf_map_area_free(array_map_vmalloc_addr(array)); + else + bpf_map_area_free(array); } static void array_map_seq_show_elem(struct bpf_map *map, void *key, @@ -444,6 +478,17 @@ static int array_map_check_btf(const struct bpf_map *map, return 0; } +int array_map_mmap(struct bpf_map *map, struct vm_area_struct *vma) +{ + struct bpf_array *array = container_of(map, struct bpf_array, map); + pgoff_t pgoff = PAGE_ALIGN(sizeof(*array)) >> PAGE_SHIFT; + + if (!(map->map_flags & BPF_F_MMAPABLE)) + return -EINVAL; + + return remap_vmalloc_range(vma, array_map_vmalloc_addr(array), pgoff); +} + const struct bpf_map_ops array_map_ops = { .map_alloc_check = array_map_alloc_check, .map_alloc = array_map_alloc, @@ -455,6 +500,7 @@ const struct bpf_map_ops array_map_ops = { .map_gen_lookup = array_map_gen_lookup, .map_direct_value_addr = array_map_direct_value_addr, .map_direct_value_meta = array_map_direct_value_meta, + .map_mmap = array_map_mmap, .map_seq_show_elem = array_map_seq_show_elem, .map_check_btf = array_map_check_btf, }; diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 52fe4bacb330..bac3becf9f90 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -127,7 +127,7 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr) return map; } -void *bpf_map_area_alloc(size_t size, int numa_node) +static void *__bpf_map_area_alloc(size_t size, int numa_node, bool mmapable) { /* We really just want to fail instead of triggering OOM killer * under memory pressure, therefore we set __GFP_NORETRY to kmalloc, @@ -142,18 +142,33 @@ void *bpf_map_area_alloc(size_t size, int numa_node) const gfp_t flags = __GFP_NOWARN | __GFP_ZERO; void *area; - if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { + /* kmalloc()'ed memory can't be mmap()'ed */ + if (!mmapable && size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { area = kmalloc_node(size, GFP_USER | __GFP_NORETRY | flags, numa_node); if (area != NULL) return area; } - + if (mmapable) { + BUG_ON(!PAGE_ALIGNED(size)); + return vmalloc_user_node_flags(size, numa_node, GFP_KERNEL | + __GFP_RETRY_MAYFAIL | flags); + } return __vmalloc_node_flags_caller(size, numa_node, GFP_KERNEL | __GFP_RETRY_MAYFAIL | flags, __builtin_return_address(0)); } +void *bpf_map_area_alloc(size_t size, int numa_node) +{ + return __bpf_map_area_alloc(size, numa_node, false); +} + +void *bpf_map_area_mmapable_alloc(size_t size, int numa_node) +{ + return __bpf_map_area_alloc(size, numa_node, true); +} + void bpf_map_area_free(void *area) { kvfree(area); @@ -425,6 +440,74 @@ static ssize_t bpf_dummy_write(struct file *filp, const char __user *buf, return -EINVAL; } +/* called for any extra memory-mapped regions (except initial) */ +static void bpf_map_mmap_open(struct vm_area_struct *vma) +{ + struct bpf_map *map = vma->vm_file->private_data; + + bpf_map_inc_with_uref(map); + + if (vma->vm_flags & VM_WRITE) { + mutex_lock(&map->freeze_mutex); + map->writecnt++; + mutex_unlock(&map->freeze_mutex); + } +} + +/* called for all unmapped memory region (including initial) */ +static void bpf_map_mmap_close(struct vm_area_struct *vma) +{ + struct bpf_map *map = vma->vm_file->private_data; + + if (vma->vm_flags & VM_WRITE) { + mutex_lock(&map->freeze_mutex); + map->writecnt--; + mutex_unlock(&map->freeze_mutex); + } + + bpf_map_put_with_uref(map); +} + +static const struct vm_operations_struct bpf_map_default_vmops = { + .open = bpf_map_mmap_open, + .close = bpf_map_mmap_close, +}; + +static int bpf_map_mmap(struct file *filp, struct vm_area_struct *vma) +{ + struct bpf_map *map = filp->private_data; + int err; + + if (!map->ops->map_mmap || map_value_has_spin_lock(map)) + return -ENOTSUPP; + + if (!(vma->vm_flags & VM_SHARED)) + return -EINVAL; + + mutex_lock(&map->freeze_mutex); + + if ((vma->vm_flags & VM_WRITE) && map->frozen) { + err = -EPERM; + goto out; + } + + /* set default open/close callbacks */ + vma->vm_ops = &bpf_map_default_vmops; + vma->vm_private_data = map; + + err = map->ops->map_mmap(map, vma); + if (err) + goto out; + + bpf_map_inc_with_uref(map); + + if (vma->vm_flags & VM_WRITE) + map->writecnt++; +out: + mutex_unlock(&map->freeze_mutex); + return err; +} + const struct file_operations bpf_map_fops = { #ifdef CONFIG_PROC_FS .show_fdinfo = bpf_map_show_fdinfo, @@ -432,6 +515,7 @@ const struct file_operations bpf_map_fops = { .release = bpf_map_release, .read = bpf_dummy_read, .write = bpf_dummy_write, + .mmap = bpf_map_mmap, }; int bpf_map_new_fd(struct bpf_map *map, int flags) @@ -577,6 +661,7 @@ static int map_create(union bpf_attr *attr) atomic64_set(&map->refcnt, 1); atomic64_set(&map->usercnt, 1); + mutex_init(&map->freeze_mutex); if (attr->btf_key_type_id || attr->btf_value_type_id) { struct btf *btf; @@ -1163,6 +1248,13 @@ static int map_freeze(const union bpf_attr *attr) map = __bpf_map_get(f); if (IS_ERR(map)) return PTR_ERR(map); + + mutex_lock(&map->freeze_mutex); + + if (map->writecnt) { + err = -EBUSY; + goto err_put; + } if (READ_ONCE(map->frozen)) { err = -EBUSY; goto err_put; @@ -1174,6 +1266,7 @@ static int map_freeze(const union bpf_attr *attr) WRITE_ONCE(map->frozen, true); err_put: + mutex_unlock(&map->freeze_mutex); fdput(f); return err; } diff --git a/mm/vmalloc.c b/mm/vmalloc.c index a3c70e275f4e..4a7d7459c4f9 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2671,6 +2671,26 @@ void *vzalloc_node(unsigned long size, int node) } EXPORT_SYMBOL(vzalloc_node); +/** + * vmalloc_user_node_flags - allocate memory for userspace on a specific node + * @size: allocation size + * @node: numa node + * @flags: flags for the page level allocator + * + * The resulting memory area is zeroed so it can be mapped to userspace + * without leaking data. + * + * Return: pointer to the allocated memory or %NULL on error + */ +void *vmalloc_user_node_flags(unsigned long size, int node, gfp_t flags) +{ + return __vmalloc_node_range(size, SHMLBA, VMALLOC_START, VMALLOC_END, + flags | __GFP_ZERO, PAGE_KERNEL, + VM_USERMAP, node, + __builtin_return_address(0)); +} +EXPORT_SYMBOL(vmalloc_user_node_flags); + /** * vmalloc_exec - allocate virtually contiguous, executable memory * @size: allocation size diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 4842a134b202..dbbcf0b02970 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -348,6 +348,9 @@ enum bpf_attach_type { /* Clone map from listener for newly accepted socket */ #define BPF_F_CLONE (1U << 9) +/* Enable memory-mapping BPF map */ +#define BPF_F_MMAPABLE (1U << 10) + /* flags for BPF_PROG_QUERY */ #define BPF_F_QUERY_EFFECTIVE (1U << 0) -- cgit