From: ndesaulniers@google.com ndesaulniers@google.com
commit 514ca14ed5444b911de59ed3381dfd195d99fe4b upstream.
Back during the discussion of commit a9a3ed1eff36 ("x86: Fix early boot crash on gcc-10, third try") we discussed the need for a function attribute to control the omission of stack protectors on a per-function basis; at the time Clang had support for no_stack_protector but GCC did not. This was fixed in gcc-11. Now that the function attribute is available, let's start using it.
Callers of boot_init_stack_canary need to use this function attribute unless they're compiled with -fno-stack-protector, otherwise the canary stored in the stack slot of the caller will differ upon the call to boot_init_stack_canary. This will lead to a call to __stack_chk_fail() then panic.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94722 Link: https://lore.kernel.org/all/20200316130414.GC12561@hirez.programming.kicks-a... Tested-by: Nathan Chancellor nathan@kernel.org Acked-by: Michael Ellerman mpe@ellerman.id.au (powerpc) Acked-by: Miguel Ojeda ojeda@kernel.org Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Nick Desaulniers ndesaulniers@google.com Link: https://lore.kernel.org/r/20230412-no_stackp-v2-1-116f9fe4bbe7@google.com Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Signed-off-by: ndesaulniers@google.com ndesaulniers@google.com --- arch/powerpc/kernel/smp.c | 1 + include/linux/compiler_attributes.h | 12 ++++++++++++ init/main.c | 3 ++- 3 files changed, 15 insertions(+), 1 deletion(-)
--- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -1605,6 +1605,7 @@ static void add_cpu_to_masks(int cpu) }
/* Activate a secondary processor. */ +__no_stack_protector void start_secondary(void *unused) { unsigned int cpu = raw_smp_processor_id(); --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -256,6 +256,18 @@ #define __noreturn __attribute__((__noreturn__))
/* + * Optional: only supported since GCC >= 11.1, clang >= 7.0. + * + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_... + * clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-protector-safeb... + */ +#if __has_attribute(__no_stack_protector__) +# define __no_stack_protector __attribute__((__no_stack_protector__)) +#else +# define __no_stack_protector +#endif + +/* * Optional: not supported by gcc. * * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable --- a/init/main.c +++ b/init/main.c @@ -877,7 +877,8 @@ static void __init print_unknown_bootopt memblock_free(unknown_options, len); }
-asmlinkage __visible void __init __no_sanitize_address __noreturn start_kernel(void) +asmlinkage __visible __init __no_sanitize_address __noreturn __no_stack_protector +void start_kernel(void) { char *command_line; char *after_dashes;