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Subject[PATCH 3.11 087/144] fs/proc/base.c: fix GPF in /proc/$PID/map_files
Date
3.11.10.7 -stable review patch.  If anyone has any objections, please let me know.

------------------

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: Luis Henriques <luis.henriques@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


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