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| author | David Gow <davidgow@google.com> | 2024-08-03 10:46:41 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-10-04 17:30:02 +0300 |
| commit | 9347605691349160768d604f6002a50610defe4a (patch) | |
| tree | d752d047c2219d21b0118f04ddf83ceee2bbd9c1 /mm | |
| parent | e1e734c1a085c263f26ecb420221587f80172088 (diff) | |
| download | linux-9347605691349160768d604f6002a50610defe4a.tar.xz | |
mm: only enforce minimum stack gap size if it's sensible
commit 69b50d4351ed924f29e3d46b159e28f70dfc707f upstream.
The generic mmap_base code tries to leave a gap between the top of the
stack and the mmap base address, but enforces a minimum gap size (MIN_GAP)
of 128MB, which is too large on some setups. In particular, on arm tasks
without ADDR_LIMIT_32BIT, the STACK_TOP value is less than 128MB, so it's
impossible to fit such a gap in.
Only enforce this minimum if MIN_GAP < MAX_GAP, as we'd prefer to honour
MAX_GAP, which is defined proportionally, so scales better and always
leaves us with both _some_ stack space and some room for mmap.
This fixes the usercopy KUnit test suite on 32-bit arm, as it doesn't set
any personality flags so gets the default (in this case 26-bit) task size.
This test can be run with: ./tools/testing/kunit/kunit.py run --arch arm
usercopy --make_options LLVM=1
Link: https://lkml.kernel.org/r/20240803074642.1849623-2-davidgow@google.com
Fixes: dba79c3df4a2 ("arm: use generic mmap top-down layout and brk randomization")
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/util.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/util.c b/mm/util.c index 2d5a309c4e54..08d494896552 100644 --- a/mm/util.c +++ b/mm/util.c @@ -434,7 +434,7 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) if (gap + pad > gap) gap += pad; - if (gap < MIN_GAP) + if (gap < MIN_GAP && MIN_GAP < MAX_GAP) gap = MIN_GAP; else if (gap > MAX_GAP) gap = MAX_GAP; |