From: Eugene Teo <eugene@redhat.com>
Date: Tue, 15 Mar 2011 03:25:17 -0400
Subject: [fs] proc: protect mm start_/end_code in /proc/pid/stat
Message-id: <20110315032517.GA25980@infradead.org>
Patchwork-id: 33993
O-Subject: [RHEL5.7] BZ#684571 CVE-2011-0726 proc: protect mm
	start_code/end_code in /proc/pid/stat
Bugzilla: 684571
CVE: CVE-2011-0726
RH-Acked-by: Amerigo Wang <amwang@redhat.com>
RH-Acked-by: Jiri Olsa <jolsa@redhat.com>
RH-Acked-by: Petr Matousek <pmatouse@redhat.com>

Backport of http://www.spinics.net/lists/mm-commits/msg82726.html.
Fixes CVE-2011-0726.

While mm->start_stack was protected from cross-uid viewing (commit f83ce3e6b02d5 ("proc: avoid information leaks to non-privileged processes")), the start_code and end_code values were not.  This would allow the text location of a PIE binary to leak, defeating ASLR.

Note that the value "1" is used instead of "0" for a protected value since "ps", "killall", and likely other readers of /proc/pid/stat, take start_code of "0" to mean a kernel thread and will misbehave.  Thanks to Brad Spengler for pointing this out.

Signed-off-by: Eugene Teo <eugene@redhat.com>
--
 fs/proc/array.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 09551b1..10611ef 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -453,8 +453,8 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
 		vsize,
 		mm ? get_mm_rss(mm) : 0,
 	        rsslim,
-		mm ? mm->start_code : 0,
-		mm ? mm->end_code : 0,
+		mm ? (permitted ? mm->start_code : 1) : 0,
+		mm ? (permitted ? mm->end_code : 1) : 0,
 		(permitted && mm) ? mm->start_stack : 0,
 		esp,
 		eip,