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| author | Kees Cook <keescook@chromium.org> | 2024-03-09 12:24:48 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-04-13 13:01:48 +0200 |
| commit | dfb2ce952143de60dd756ed666901236c76cb3fa (patch) | |
| tree | f1264032613f4a99a119e8299bde4f7e0b7e1fdf | |
| parent | 7cfee26d1950250b14c5cb0a37b142f3fcc6396a (diff) | |
| download | linux-stable-dfb2ce952143de60dd756ed666901236c76cb3fa.tar.gz linux-stable-dfb2ce952143de60dd756ed666901236c76cb3fa.tar.bz2 linux-stable-dfb2ce952143de60dd756ed666901236c76cb3fa.zip | |
randomize_kstack: Improve entropy diffusion
[ Upstream commit 9c573cd313433f6c1f7236fe64b9b743500c1628 ]
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: 39218ff4c625 ("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: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | include/linux/randomize_kstack.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/randomize_kstack.h b/include/linux/randomize_kstack.h index d373f1bcbf7c..5d52d15faee0 100644 --- a/include/linux/randomize_kstack.h +++ b/include/linux/randomize_kstack.h @@ -58,7 +58,7 @@ DECLARE_PER_CPU(u32, kstack_offset); 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) |