brk: COMPAT_BRK: fix detection of randomized brk
authorJiri Kosina <jkosina@suse.cz>
Thu, 14 Apr 2011 22:22:09 +0000 (15:22 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 14 Apr 2011 23:06:55 +0000 (16:06 -0700)
commit4471a675dfc7ca676c165079e91c712b09dc9ce4
tree9746321a818cefbb2aa97d8ac4d44c4a6ae84f5a
parent5de1743e2434fcb24e3d944a20130029b8fe867a
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>
fs/binfmt_elf.c
include/linux/sched.h
mm/mmap.c