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authorJiri Kosina <jkosina@suse.cz>2011-04-14 15:22:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-04-14 16:06:55 -0700
commit4471a675dfc7ca676c165079e91c712b09dc9ce4 (patch)
tree9746321a818cefbb2aa97d8ac4d44c4a6ae84f5a
parent5de1743e2434fcb24e3d944a20130029b8fe867a (diff)
downloadop-kernel-dev-4471a675dfc7ca676c165079e91c712b09dc9ce4.zip
op-kernel-dev-4471a675dfc7ca676c165079e91c712b09dc9ce4.tar.gz
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>
-rw-r--r--fs/binfmt_elf.c6
-rw-r--r--include/linux/sched.h3
-rw-r--r--mm/mmap.c2
3 files changed, 9 insertions, 2 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index f34078d..303983f 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -941,9 +941,13 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
current->mm->start_stack = bprm->p;
#ifdef arch_randomize_brk
- if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1))
+ if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1)) {
current->mm->brk = current->mm->start_brk =
arch_randomize_brk(current->mm);
+#ifdef CONFIG_COMPAT_BRK
+ current->brk_randomized = 1;
+#endif
+ }
#endif
if (current->personality & MMAP_PAGE_ZERO) {
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4ec2c02..18d63ce 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1254,6 +1254,9 @@ struct task_struct {
#endif
struct mm_struct *mm, *active_mm;
+#ifdef CONFIG_COMPAT_BRK
+ unsigned brk_randomized:1;
+#endif
#if defined(SPLIT_RSS_COUNTING)
struct task_rss_stat rss_stat;
#endif
diff --git a/mm/mmap.c b/mm/mmap.c
index 8c05e5b..e27e0cf 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -259,7 +259,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
* randomize_va_space to 2, which will still cause mm->start_brk
* to be arbitrarily shifted
*/
- if (mm->start_brk > PAGE_ALIGN(mm->end_data))
+ if (current->brk_randomized)
min_brk = mm->start_brk;
else
min_brk = mm->end_data;
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