[lucid/fsl-imx51, maverick/ti-omap4, natty/ti-omap4][PATCH] proc: fix oops on invalid /proc/<pid>/maps access, CVE-2011-1020

[Herton R. Krzesinski]

From: Linus Torvalds <torvalds at linux-foundation.org>

When m_start returns an error, the seq_file logic will still call m_stop
with that error entry, so we'd better make sure that we check it before
using it as a vma.

Introduced by commit ec6fd8a4355c ("report errors in /proc/*/*map*
sanely"), which replaced NULL with various ERR_PTR() cases.

(On ia64, you happen to get a unaligned fault instead of a page fault,
since the address used is generally some random error code like -EPERM)

Reported-by: Anca Emanuel <anca.emanuel at gmail.com>
Reported-by: Tony Luck <tony.luck at intel.com>
Cc: Al Viro <viro at zeniv.linux.org.uk>
Cc: Américo Wang <xiyou.wangcong at gmail.com>
Cc: Stephen Wilson <wilsons at start.ca>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry picked from commit 76597cd31470fa130784c78fadb4dab2e624a723)
CVE-2011-1020
BugLink: http://bugs.launchpad.net/bugs/813026
Signed-off-by: Herton R. Krzesinski <herton.krzesinski at canonical.com>

---
 fs/proc/task_mmu.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

This is already applied on lucid, maverick and natty master/master-next,
but is required also on lucid/fsl-imx51, maverick/ti-omap4,
natty/ti-omap4

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7c708a4..2e7addf 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -182,7 +182,8 @@ static void m_stop(struct seq_file *m, void *v)
 	struct proc_maps_private *priv = m->private;
 	struct vm_area_struct *vma = v;
 
-	vma_stop(priv, vma);
+	if (!IS_ERR(vma))
+		vma_stop(priv, vma);
 	if (priv->task)
 		put_task_struct(priv->task);
 }
-- 
1.7.4.1