[3.11.y.z extended stable] Patch "fs/proc/base.c: fix GPF in /proc/$PID/map_files" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    fs/proc/base.c: fix GPF in /proc/$PID/map_files

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 536107437500f537fce24f8eed09bb5d40fb6012 Mon Sep 17 00:00:00 2001
From: Artem Fetishev <artem_fetishev at epam.com>
Date: Mon, 10 Mar 2014 15:49:45 -0700
Subject: fs/proc/base.c: fix GPF in /proc/$PID/map_files

commit 70335abb2689c8cd5df91bf2d95a65649addf50b upstream.

The expected logic of proc_map_files_get_link() is either to return 0
and initialize 'path' or return an error and leave 'path' uninitialized.

By the time dname_to_vma_addr() returns 0 the corresponding vma may have
already be gone.  In this case the path is not initialized but the
return value is still 0.  This results in 'general protection fault'
inside d_path().

Steps to reproduce:

  CONFIG_CHECKPOINT_RESTORE=y

    fd = open(...);
    while (1) {
        mmap(fd, ...);
        munmap(fd, ...);
    }

  ls -la /proc/$PID/map_files

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=68991

Signed-off-by: Artem Fetishev <artem_fetishev at epam.com>
Signed-off-by: Aleksandr Terekhov <aleksandr_terekhov at epam.com>
Reported-by: <wiebittewas at gmail.com>
Acked-by: Pavel Emelyanov <xemul at parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov at openvz.org>
Reviewed-by: "Eric W. Biederman" <ebiederm at xmission.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/proc/base.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1485e38..c35eaa4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1813,6 +1813,7 @@ static int proc_map_files_get_link(struct dentry *dentry, struct path *path)
 	if (rc)
 		goto out_mmput;

+	rc = -ENOENT;
 	down_read(&mm->mmap_sem);
 	vma = find_exact_vma(mm, vm_start, vm_end);
 	if (vma && vma->vm_file) {
--
1.9.1