From: Oleg Nesterov <oleg@redhat.com>
Date: Tue, 31 Jan 2012 16:14:38 +0000 (+0100)
Subject: proc: mem_release() should check mm != NULL
X-Git-Tag: firefly_0821_release~7541^2~1803
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=401f63716ca0bca1728e55ccf2132fb3785cf5da;p=firefly-linux-kernel-4.4.55.git

proc: mem_release() should check mm != NULL

commit 71879d3cb3dd8f2dfdefb252775c1b3ea04a3dd4 upstream.

mem_release() can hit mm == NULL, add the necessary check.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
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 7b28f27ad80b..b3e298f29421 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -886,8 +886,8 @@ loff_t mem_lseek(struct file *file, loff_t offset, int orig)
 static int mem_release(struct inode *inode, struct file *file)
 {
 	struct mm_struct *mm = file->private_data;
-
-	mmput(mm);
+	if (mm)
+		mmput(mm);
 	return 0;
 }