Commit e001ef96 authored Jul 10, 2025 by Xuanye Liu Committed by Andrew Morton Jul 19, 2025

mm: simplify min_brk handling in brk()

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>

parent c8095793

mm/mmap.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -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;