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Patch series "mm: Care about shadow stack guard gap when getting an
unmapped area", v2.
As covered in the commit log for c44357c2e76b ("x86/mm: care about shadow
stack guard gap during placement") our current mmap() implementation does
not take care to ensure that a new mapping isn't placed with existing
mappings inside it's own guard gaps. This is particularly important for
shadow stacks since if two shadow stacks end up getting placed adjacent to
each other then they can overflow into each other which weakens the
protection offered by the feature.
On x86 there is a custom arch_get_unmapped_area() which was updated by the
above commit to cover this case by specifying a start_gap for allocations
with VM_SHADOW_STACK. Both arm64 and RISC-V have equivalent features and
use the generic implementation of arch_get_unmapped_area() so let's make
the equivalent change there so they also don't get shadow stack pages
placed without guard pages. The arm64 and RISC-V shadow stack
implementations are currently on the list:
https://lore.kernel.org/r/20240829-arm64-gcs-v12-0-42fec94743
https://lore.kernel.org/lkml/[email protected]/
Given the addition of the use of vm_flags in the generic implementation we
also simplify the set of possibilities that have to be dealt with in the
core code by making arch_get_unmapped_area() take vm_flags as standard.
This is a bit invasive since the prototype change touches quite a few
architectures but since the parameter is ignored the change is
straightforward, the simplification for the generic code seems worth it.
This patch (of 3):
When we introduced arch_get_unmapped_area_vmflags() in 961148704acd ("mm:
introduce arch_get_unmapped_area_vmflags()") we did so as part of properly
supporting guard pages for shadow stacks on x86_64, which uses a custom
arch_get_unmapped_area(). Equivalent features are also present on both
arm64 and RISC-V, both of which use the generic implementation of
arch_get_unmapped_area() and will require equivalent modification there.
Rather than continue to deal with having two versions of the functions
let's bite the bullet and have all implementations of
arch_get_unmapped_area() take vm_flags as a parameter.
The new parameter is currently ignored by all implementations other than
x86. The only caller that doesn't have a vm_flags available is
mm_get_unmapped_area(), as for the x86 implementation and the wrapper used
on other architectures this is modified to supply no flags.
No functional changes.
Link: https://lkml.kernel.org/r/20240904-mm-generic-shadow-stack-guard-v2-0-a46b8b6dc0ed@kernel.org
Link: https://lkml.kernel.org/r/20240904-mm-generic-shadow-stack-guard-v2-1-a46b8b6dc0ed@kernel.org
Signed-off-by: Mark Brown <[email protected]>
Acked-by: Lorenzo Stoakes <[email protected]>
Reviewed-by: Liam R. Howlett <[email protected]>
Acked-by: Helge Deller <[email protected]> [parisc]
Cc: Alexander Gordeev <[email protected]>
Cc: Andreas Larsson <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: "Edgecombe, Rick P" <[email protected]>
Cc: Gerald Schaefer <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ivan Kokshaysky <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: John Paul Adrian Glaubitz <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Naveen N Rao <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Russell King <[email protected]>
Cc: Sven Schnelle <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: WANG Xuerui <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Future changes will need to add a new member to struct
vm_unmapped_area_info. This would cause trouble for any call site that
doesn't initialize the struct. Currently every caller sets each member
manually, so if new ones are added they will be uninitialized and the core
code parsing the struct will see garbage in the new member.
It could be possible to initialize the new member manually to 0 at each
call site. This and a couple other options were discussed. Having some
struct vm_unmapped_area_info instances not zero initialized will put those
sites at risk of feeding garbage into vm_unmapped_area(), if the
convention is to zero initialize the struct and any new field addition
missed a call site that initializes each field manually. So it is useful
to do things similar across the kernel.
The consensus (see links) was that in general the best way to accomplish
taking into account both code cleanliness and minimizing the chance of
introducing bugs, was to do C99 static initialization. As in: struct
vm_unmapped_area_info info = {};
With this method of initialization, the whole struct will be zero
initialized, and any statements setting fields to zero will be unneeded.
The change should not leave cleanup at the call sides.
While iterating though the possible solutions a few archs kindly acked
other variations that still zero initialized the struct. These sites have
been modified in previous changes using the pattern acked by the
respective arch.
So to be reduce the chance of bugs via uninitialized fields, perform a
tree wide change using the consensus for the best general way to do this
change. Use C99 static initializing to zero the struct and remove and
statements that simply set members to zero.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lore.kernel.org/lkml/202402280912.33AEE7A9CF@keescook/#t
Link: https://lore.kernel.org/lkml/j7bfvig3gew3qruouxrh7z7ehjjafrgkbcmg6tcghhfh3rhmzi@wzlcoecgy5rs/
Link: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Rick Edgecombe <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Borislav Petkov (AMD) <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Deepak Gupta <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: H. Peter Anvin (Intel) <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Naveen N. Rao <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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This enables ARCH_HAS_VM_GET_PAGE_PROT on the platform and exports
standard vm_get_page_prot() implementation via DECLARE_VM_GET_PAGE_PROT,
which looks up a private and static protection_map[] array. Subsequently
all __SXXX and __PXXX macros can be dropped which are no longer needed.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Anshuman Khandual <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Brian Cain <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Jonas Bonn <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Russell King <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Cc: Stafford Horne <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: WANG Xuerui <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.
This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.
Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.
One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications. For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).
Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.
Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.
Original-patch-by: Oleg Nesterov <[email protected]>
Original-patch-by: Michal Hocko <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Signed-off-by: Linus Torvalds <[email protected]>
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to <linux/sched/mm.h>
We are going to split more MM APIs out of <linux/sched.h>, which
will have to be picked up from a couple of .c files.
The APIs that we are going to move are:
arch_pick_mmap_layout()
arch_get_unmapped_area()
arch_get_unmapped_area_topdown()
mm_update_next_owner()
Include the header in the files that are going to need it.
Acked-by: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
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Merge misc updates from Andrew Morton:
"About half of most of MM. Going very early this time due to
uncertainty over the coreautounifiednumasched things. I'll send the
other half of most of MM tomorrow. The rest of MM awaits a slab merge
from Pekka."
* emailed patches from Andrew Morton: (71 commits)
memory_hotplug: ensure every online node has NORMAL memory
memory_hotplug: handle empty zone when online_movable/online_kernel
mm, memory-hotplug: dynamic configure movable memory and portion memory
drivers/base/node.c: cleanup node_state_attr[]
bootmem: fix wrong call parameter for free_bootmem()
avr32, kconfig: remove HAVE_ARCH_BOOTMEM
mm: cma: remove watermark hacks
mm: cma: skip watermarks check for already isolated blocks in split_free_page()
mm, oom: fix race when specifying a thread as the oom origin
mm, oom: change type of oom_score_adj to short
mm: cleanup register_node()
mm, mempolicy: remove duplicate code
mm/vmscan.c: try_to_freeze() returns boolean
mm: introduce putback_movable_pages()
virtio_balloon: introduce migration primitives to balloon pages
mm: introduce compaction and migration for ballooned pages
mm: introduce a common interface for balloon pages mobility
mm: redefine address_space.assoc_mapping
mm: adjust address_space_operations.migratepage() return code
arch/sparc/kernel/sys_sparc_64.c: s/COLOUR/COLOR/
...
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Update the sh arch_get_unmapped_area[_topdown] functions to make use of
vm_unmapped_area() instead of implementing a brute force search.
[[email protected]: remove now-unused COLOUR_ALIGN_DOWN()]
Signed-off-by: Michel Lespinasse <[email protected]>
Reviewed-by: Rik van Riel <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Russell King <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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This patch fixes the /dev/mem driver to use phys_addr_t for physical
addresses. This is required on PAE systems, especially those that run
entirely out of >4G physical memory space.
Signed-off-by: Cyril Chemparathy <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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We want addr - (pgoff << PAGE_SHIFT) consistently coloured...
Acked-by: Paul Mundt <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Signed-off-by: Al Viro <[email protected]>
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This does a bit of reorganizing for allowing nommu to use the new
and generic cache.c, no functional changes.
Signed-off-by: Paul Mundt <[email protected]>
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Presently shm_align_mask is only looked at for the bottom up case, but we
still want this for proper colouring constraints in the topdown case.
Signed-off-by: Paul Mundt <[email protected]>
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Now that arch/sh/mm/mmap.c exists, move arch_get_unmapped_area() there.
Follows the ARM change.
Signed-off-by: Paul Mundt <[email protected]>
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Signed-off-by: Paul Mundt <[email protected]>
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With the PMB enabled, only P1SEG and up are covered by the PMB mappings,
meaning that situations where out-of-bounds physical addresses are read
from will lead to TLB reset after the PMB miss, allowing for use cases
like dd if=/dev/mem to reset the TLB.
Fix this up to make sure the reference is between __MEMORY_START (phys)
and __pa(high_memory). This is coherent across all variants of sh/sh64
with and without MMU, though the PMB bug itself is only applicable to
SH-4A parts.
Reported-by: Hideo Saito <[email protected]>
Signed-off-by: Paul Mundt <[email protected]>
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