From: Artem Fetishev <artem_fetishev@epam.com>
Date: Mon, 10 Mar 2014 22:49:45 +0000 (-0700)
Subject: fs/proc/base.c: fix GPF in /proc/$PID/map_files
X-Git-Tag: firefly_0821_release~3679^2~2607
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=63490f40e071a1b03b6ceca4b654a4d5aeff851d;p=firefly-linux-kernel-4.4.55.git

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@epam.com>
Signed-off-by: Aleksandr Terekhov <aleksandr_terekhov@epam.com>
Reported-by: <wiebittewas@gmail.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/proc/base.c b/fs/proc/base.c
index c3834dad09b3..de12b8128b95 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1825,6 +1825,7 @@ 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) {