brk: COMPAT_BRK: fix detection of randomized brk
5520e89
("brk: fix min_brk lower bound computation for COMPAT_BRK")
tried to get the whole logic of brk randomization for legacy
(libc5-based) applications finally right.
It turns out that the way to detect whether brk has actually been
randomized in the end or not introduced by that patch still doesn't work
for those binaries, as reported by Geert:
: /sbin/init from my old m68k ramdisk exists prematurely.
:
: Before the patch:
:
: | brk(0x80005c8e) = 0x80006000
:
: After the patch:
:
: | brk(0x80005c8e) = 0x80005c8e
:
: Old libc5 considers brk() to have failed if the return value is not
: identical to the requested value.
I don't like it, but currently see no better option than a bit flag in
task_struct to catch the CONFIG_COMPAT_BRK && randomize_va_space == 2
case.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
5de1743e24
commit
4471a675df
3 changed files with 9 additions and 2 deletions
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@ -941,9 +941,13 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
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current->mm->start_stack = bprm->p;
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#ifdef arch_randomize_brk
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if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1))
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if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1)) {
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current->mm->brk = current->mm->start_brk =
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arch_randomize_brk(current->mm);
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#ifdef CONFIG_COMPAT_BRK
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current->brk_randomized = 1;
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#endif
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}
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#endif
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if (current->personality & MMAP_PAGE_ZERO) {
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@ -1254,6 +1254,9 @@ struct task_struct {
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#endif
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struct mm_struct *mm, *active_mm;
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#ifdef CONFIG_COMPAT_BRK
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unsigned brk_randomized:1;
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#endif
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#if defined(SPLIT_RSS_COUNTING)
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struct task_rss_stat rss_stat;
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#endif
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@ -259,7 +259,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
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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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if (current->brk_randomized)
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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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