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randomize_kstack: Improve entropy diffusion 

JIRA: https://issues.redhat.com/browse/RHEL-37308
CVE: CVE-2024-35918

commit 9c573cd313433f6c1f7236fe64b9b743500c1628
Author: Kees Cook <keescook@chromium.org>
Date:   Sat Mar 9 12:24:48 2024 -0800

    randomize_kstack: Improve entropy diffusion

    The kstack_offset variable was really only ever using the low bits for
    kernel stack offset entropy. Add a ror32() to increase bit diffusion.

    Suggested-by: Arnd Bergmann <arnd@arndb.de>
    Fixes: 39218ff4c6 ("stack: Optionally randomize kernel stack offset each syscall")
    Link: https://lore.kernel.org/r/20240309202445.work.165-kees@kernel.org
    Signed-off-by: Kees Cook <keescook@chromium.org>

Signed-off-by: Chris von Recklinghausen <crecklin@redhat.com>
This commit is contained in:
Chris von Recklinghausen 2024-05-31 07:04:59 -04:00
parent 0e5b8cd587
commit cbe61b95fc
1 changed files with 1 additions and 1 deletions
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2
include/linux/randomize_kstack.h
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@ -47,7 +47,7 @@ void *__builtin_alloca(size_t size);
if (static_branch_maybe(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT, \
&randomize_kstack_offset)) { \
u32 offset = raw_cpu_read(kstack_offset); \
offset ^= (rand); \
offset = ror32(offset, 5) ^ (rand); \
raw_cpu_write(kstack_offset, offset); \
} \
} while (0)