[PATCH 3.4 23/35] fs/proc/base.c: fix GPF in /proc/$PID/map_files

Greg Kroah-Hartman
2014-03-21T00:09:56Z

From: Artem Fetishev <artem_fetishev@epam.com>

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>

---
fs/proc/base.c | 1 +
1 file changed, 1 insertion(+)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2092,6 +2092,7 @@ static int proc_map_files_get_link(struc
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) {