On Fri, Oct 11, 2024 at 03:58:04PM +0300, Mike Rapoport wrote:
> I overlooked how cfi_*_callers routines update addr.
> This patch should fix it:
Thanks, can confirm. My boot is working again and LKDTM's
CFI_FORWARD_PROTO test properly fails.
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 3b3fa93af3b1..cf782f431110 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -1148,11 +1148,13 @@ static int cfi_disable_callers(s32 *start, s32 *end, struct module *mod)
>
> for (s = start; s < end; s++) {
> void *addr = (void *)s + *s;
> - void *wr_addr = module_writable_address(mod, addr);
> + void *wr_addr;
> u32 hash;
>
> addr -= fineibt_caller_size;
> - hash = decode_caller_hash(addr);
> + wr_addr = module_writable_address(mod, addr);
> + hash = decode_caller_hash(wr_addr);
> +
> if (!hash) /* nocfi callers */
> continue;
>
> @@ -1172,11 +1174,12 @@ static int cfi_enable_callers(s32 *start, s32 *end, struct module *mod)
>
> for (s = start; s < end; s++) {
> void *addr = (void *)s + *s;
> - void *wr_addr = module_writable_address(mod, addr);
> + void *wr_addr;
> u32 hash;
>
> addr -= fineibt_caller_size;
> - hash = decode_caller_hash(addr);
> + wr_addr = module_writable_address(mod, addr);
> + hash = decode_caller_hash(wr_addr);
> if (!hash) /* nocfi callers */
> continue;
>
> @@ -1249,11 +1252,12 @@ static int cfi_rand_callers(s32 *start, s32 *end, struct module *mod)
>
> for (s = start; s < end; s++) {
> void *addr = (void *)s + *s;
> - void *wr_addr = module_writable_address(mod, addr);
> + void *wr_addr;
> u32 hash;
>
> addr -= fineibt_caller_size;
> - hash = decode_caller_hash(addr);
> + wr_addr = module_writable_address(mod, addr);
> + hash = decode_caller_hash(wr_addr);
> if (hash) {
> hash = -cfi_rehash(hash);
> text_poke_early(wr_addr + 2, &hash, 4);
> @@ -1269,14 +1273,15 @@ static int cfi_rewrite_callers(s32 *start, s32 *end, struct module *mod)
>
> for (s = start; s < end; s++) {
> void *addr = (void *)s + *s;
> - void *wr_addr = module_writable_address(mod, addr);
> + void *wr_addr;
> u32 hash;
>
> addr -= fineibt_caller_size;
> - hash = decode_caller_hash(addr);
> + wr_addr = module_writable_address(mod, addr);
> + hash = decode_caller_hash(wr_addr);
> if (hash) {
> text_poke_early(wr_addr, fineibt_caller_start, fineibt_caller_size);
> - WARN_ON(*(u32 *)(addr + fineibt_caller_hash) != 0x12345678);
> + WARN_ON(*(u32 *)(wr_addr + fineibt_caller_hash) != 0x12345678);
> text_poke_early(wr_addr + fineibt_caller_hash, &hash, 4);
> }
> /* rely on apply_retpolines() */
>
> > Cheers,
> > Nathan
>
> --
> Sincerely yours,
> Mike.
