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x86/elf: Correct comment for STACK_RND_MASK()

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Commit 913bd90601 ("[PATCH] x86_64: Increase the variability of the
process stack on 64bit architectures"), merged in 2006, increased stack
randomisation from 8 MiB to an ostensible 1 GiB for 64-bit systems.

However the commit actually introduced a mask of 0x3fffff * 4 KiB pages
which provides 16 GiB of randomisation, not 1 GiB.

It appears Andi perhaps typo'd an additional 'f', as 0x3ffff would indeed
provide the stated 1 GiB.

Since this value has been in use for 20 years it seems sensible to retain
it, so correct the comment instead.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Acked-by: SJ Park <sj@kernel.org>
Link: https://patch.msgid.link/20260722-fix-x86-comment-v1-1-605080af988d@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Lorenzo Stoakes (ARM) 2026-07-22 19:44:43 +01:00 committed by Kees Cook
parent 8cdeaa50ea
commit ab11176bd3
1 changed files with 1 additions and 1 deletions
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2
arch/x86/include/asm/elf.h
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@ -322,7 +322,7 @@ extern unsigned long get_sigframe_size(void);
#else /* CONFIG_X86_32 */
/* 1GB for 64bit, 8MB for 32bit */
/* 16GB for 64bit, 8MB for 32bit */
#define __STACK_RND_MASK(is32bit) ((is32bit) ? 0x7ff : 0x3fffff)
#define STACK_RND_MASK __STACK_RND_MASK(mmap_is_ia32())