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mm: simplify min_brk handling in brk()

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Set min_brk to mm->start_brk by default, and override it with mm->end_data
only when CONFIG_COMPAT_BRK is enabled and brk_randomized is false.

This makes the logic clearer with no functional change.

Link: https://lkml.kernel.org/r/20250710025859.926355-1-liuqiye2025@163.com
Signed-off-by: Xuanye Liu <liuqiye2025@163.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Xuanye Liu
2025-07-10 10:58:58 +08:00
committed by Andrew Morton
parent c809579374
commit e001ef9652
1 changed files with 2 additions and 5 deletions
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7
mm/mmap.c
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@@ -127,18 +127,15 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
origbrk = mm->brk;
min_brk = mm->start_brk;
#ifdef CONFIG_COMPAT_BRK
/*
* CONFIG_COMPAT_BRK can still be overridden by setting
* randomize_va_space to 2, which will still cause mm->start_brk
* to be arbitrarily shifted
*/
if (current->brk_randomized)
min_brk = mm->start_brk;
else
if (!current->brk_randomized)
min_brk = mm->end_data;
#else
min_brk = mm->start_brk;
#endif
if (brk < min_brk)
goto out;