Re: [PATCH v5 8/8] lkdtm/powerpc: Fix code patching hijack test
From: Christophe Leroy <hidden>
Date: 2021-08-05 09:18:37
Also in:
linux-hardening
Le 13/07/2021 à 07:31, Christopher M. Riedl a écrit :
Code patching on powerpc with a STRICT_KERNEL_RWX uses a userspace address in a temporary mm on Radix now. Use __put_user() to avoid write failures due to KUAP when attempting a "hijack" on the patching address. __put_user() also works with the non-userspace, vmalloc-based patching address on non-Radix MMUs.
It is not really clean to use __put_user() on non user address, allthought it works by change. I think it would be better to do something like if (is_kernel_addr(addr)) copy_to_kernel_nofault(...); else copy_to_user_nofault(...);
quoted hunk ↗ jump to hunk
Signed-off-by: Christopher M. Riedl <redacted> --- drivers/misc/lkdtm/perms.c | 9 --------- 1 file changed, 9 deletions(-)diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 41e87e5f9cc86..da6a34a0a49fb 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c@@ -262,16 +262,7 @@ static inline u32 lkdtm_read_patch_site(void) /* Returns True if the write succeeds */ static inline bool lkdtm_try_write(u32 data, u32 *addr) { -#ifdef CONFIG_PPC - __put_kernel_nofault(addr, &data, u32, err); - return true; - -err: - return false; -#endif -#ifdef CONFIG_X86_64 return !__put_user(data, addr); -#endif } static int lkdtm_patching_cpu(void *data)