close race in /proc/*/environ, CVE-2011-1020

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@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@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index e406d56..3803523 100644 (file)
--- 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;