[natty,natty/ti-omap4 CVE 3/5] close race in /proc/*/environ

[Andy Whitcroft]

From: Al Viro <viro at zeniv.linux.org.uk>

Switch to mm_for_maps().  Maybe we ought to make it r--r--r--,
since we do checks on IO anyway...

Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>

(cherry picked from commit d6f64b89d7ff22ce05896ab4a93a653e8d0b123d)
CVE-2011-1020
BugLink: http://bugs.launchpad.net/bugs/813026
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 fs/proc/base.c |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index e406d56..3803523 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -919,20 +919,18 @@ static ssize_t environ_read(struct file *file, char __user *buf,
 	if (!task)
 		goto out_no_task;
 
-	if (!ptrace_may_access(task, PTRACE_MODE_READ))
-		goto out;
-
 	ret = -ENOMEM;
 	page = (char *)__get_free_page(GFP_TEMPORARY);
 	if (!page)
 		goto out;
 
-	ret = 0;
 
-	mm = get_task_mm(task);
-	if (!mm)
+	mm = mm_for_maps(task);
+	ret = PTR_ERR(mm);
+	if (!mm || IS_ERR(mm))
 		goto out_free;
 
+	ret = 0;
 	while (count > 0) {
 		int this_len, retval, max_len;
 
-- 
1.7.4.1