[PATCH 3.8 67/86] fs/proc/base.c: fix GPF in /proc/$PID/map_files

From: Kamal Mostafa
Date: Tue Apr 01 2014 - 12:40:00 EST -stable review patch. If anyone has any objections, please let me know.


From: Artem Fetishev <artem_fetishev@xxxxxxxx>

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:


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@xxxxxxxx>
Signed-off-by: Aleksandr Terekhov <aleksandr_terekhov@xxxxxxxx>
Reported-by: <wiebittewas@xxxxxxxxx>
Acked-by: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Acked-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Reviewed-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
fs/proc/base.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 9b43ff77..78150a0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1784,6 +1784,7 @@ static int proc_map_files_get_link(struct dentry *dentry, struct path *path)
if (rc)
goto out_mmput;

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

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