From: Kees Cook keescook@chromium.org

stable inclusion from stable-v6.6.27 commit 300a2b9c2b28282974ee300bb5d5025cbbb1f64c category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB0K55

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ 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 Signed-off-by: Gu Bowen gubowen5@huawei.com --- include/linux/randomize_kstack.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/randomize_kstack.h b/include/linux/randomize_kstack.h index 91f1b990a3c3..2cfdc53f01f7 100644 --- a/include/linux/randomize_kstack.h +++ b/include/linux/randomize_kstack.h @@ -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)