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x86/boot: Disable stack protector for early boot code

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On 64-bit, this will prevent crashes when the canary access is changed
from %gs:40 to %gs:__stack_chk_guard(%rip).  RIP-relative addresses from
the identity-mapped early boot code will target the wrong address with
zero-based percpu.  KASLR could then shift that address to an unmapped
page causing a crash on boot.

This early boot code runs well before user-space is active and does not
need stack protector enabled.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250123190747.745588-4-brgerst@gmail.com
This commit is contained in:
Brian Gerst
2025-01-23 14:07:35 -05:00
committed by Ingo Molnar
parent 0ee2689b93
commit a9a76b38aa
1 changed files with 2 additions and 0 deletions
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2
arch/x86/kernel/Makefile
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@@ -44,6 +44,8 @@ KCOV_INSTRUMENT_unwind_orc.o := n
KCOV_INSTRUMENT_unwind_frame.o := n
KCOV_INSTRUMENT_unwind_guess.o := n
CFLAGS_head32.o := -fno-stack-protector
CFLAGS_head64.o := -fno-stack-protector
CFLAGS_irq.o := -I $(src)/../include/asm/trace
obj-y += head_$(BITS).o