From: P J P <ppandit@redhat.com>
Date: Wed, 3 Apr 2013 02:38:00 +0000 (+0900)
Subject: f2fs: add NULL pointer check
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=cfb185a1488810fbae9256c7d52f66c558c6ea04;p=openwrt%2Fstaging%2Fblogic.git

f2fs: add NULL pointer check

Commit - fa9150a84c - replaces a call to generic_writepages() in
f2fs_write_data_pages() with write_cache_pages(), with a function pointer
argument pointing to routine: __f2fs_writepage.

  -> https://git.kernel.org/linus/fa9150a84ca333f68127097c4fa1eda4b3913a22

  This patch adds a NULL pointer check in f2fs_write_data_pages() to avoid
  a possible NULL pointer dereference, in case if - mapping->a_ops->writepage -
  is NULL.

Signed-off-by: P J P <ppandit@redhat.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
---

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 47a2d7c87ea9..cf9ff5f76134 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -559,6 +559,10 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 	int ret;
 	long excess_nrtw = 0, desired_nrtw;
 
+	/* deal with chardevs and other special file */
+	if (!mapping->a_ops->writepage)
+		return 0;
+
 	if (wbc->nr_to_write < MAX_DESIRED_PAGES_WP) {
 		desired_nrtw = MAX_DESIRED_PAGES_WP;
 		excess_nrtw = desired_nrtw - wbc->nr_to_write;