brk: fix min_brk lower bound computation for COMPAT_BRK
Even if CONFIG_COMPAT_BRK is set in the kernel configuration, it can still
be overriden by randomize_va_space sysctl.
If this is the case, the min_brk computation in sys_brk() implementation
is wrong, as it solely takes into account COMPAT_BRK setting, assuming
that brk start is not randomized. But that might not be the case if
randomize_va_space sysctl has been set to '2' at the time the binary has
been loaded from disk.
In such case, the check has to be done in a same way as in
!CONFIG_COMPAT_BRK case.
In addition to that, the check for the COMPAT_BRK case introduced back in
a5b4592c
("brk: make sys_brk() honor COMPAT_BRK when computing lower
bound") is slightly wrong -- the lower bound shouldn't be mm->end_code,
but mm->end_data instead, as that's where the legacy applications expect
brk section to start (i.e. immediately after last global variable).
[akpm@linux-foundation.org: fix comment]
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
32d6feadf4
commit
5520e89485
10
mm/mmap.c
10
mm/mmap.c
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@ -254,7 +254,15 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
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down_write(&mm->mmap_sem);
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down_write(&mm->mmap_sem);
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#ifdef CONFIG_COMPAT_BRK
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#ifdef CONFIG_COMPAT_BRK
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min_brk = mm->end_code;
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/*
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* CONFIG_COMPAT_BRK can still be overridden by setting
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* randomize_va_space to 2, which will still cause mm->start_brk
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* to be arbitrarily shifted
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*/
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if (mm->start_brk > PAGE_ALIGN(mm->end_data))
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min_brk = mm->start_brk;
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else
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min_brk = mm->end_data;
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#else
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#else
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min_brk = mm->start_brk;
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min_brk = mm->start_brk;
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#endif
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#endif
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