randomize_kstack: Improve entropy diffusion
authorKees Cook <keescook@chromium.org>
Sat, 9 Mar 2024 20:24:48 +0000 (12:24 -0800)
committerKees Cook <keescook@chromium.org>
Wed, 3 Apr 2024 21:45:03 +0000 (14:45 -0700)
commit9c573cd313433f6c1f7236fe64b9b743500c1628
tree69e9397102c2704709368fb199287944bb295a4d
parentbbda3ba626b9f57ff6063058877eca856f5b734d
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: 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>
include/linux/randomize_kstack.h