--- /dev/null
+From 5e1021f2b6dff1a86a468a1424d59faae2bc63c1 Mon Sep 17 00:00:00 2001
+From: Eryu Guan <guaneryu@gmail.com>
+Date: Sat, 12 Mar 2016 21:40:32 -0500
+Subject: ext4: fix NULL pointer dereference in ext4_mark_inode_dirty()
+
+From: Eryu Guan <guaneryu@gmail.com>
+
+commit 5e1021f2b6dff1a86a468a1424d59faae2bc63c1 upstream.
+
+ext4_reserve_inode_write() in ext4_mark_inode_dirty() could fail on
+error (e.g. EIO) and iloc.bh can be NULL in this case. But the error is
+ignored in the following "if" condition and ext4_expand_extra_isize()
+might be called with NULL iloc.bh set, which triggers NULL pointer
+dereference.
+
+This is uncovered by commit 8b4953e13f4c ("ext4: reserve code points for
+the project quota feature"), which enlarges the ext4_inode size, and
+run the following script on new kernel but with old mke2fs:
+
+ #/bin/bash
+ mnt=/mnt/ext4
+ devname=ext4-error
+ dev=/dev/mapper/$devname
+ fsimg=/home/fs.img
+
+ trap cleanup 0 1 2 3 9 15
+
+ cleanup()
+ {
+ umount $mnt >/dev/null 2>&1
+ dmsetup remove $devname
+ losetup -d $backend_dev
+ rm -f $fsimg
+ exit 0
+ }
+
+ rm -f $fsimg
+ fallocate -l 1g $fsimg
+ backend_dev=`losetup -f --show $fsimg`
+ devsize=`blockdev --getsz $backend_dev`
+
+ good_tab="0 $devsize linear $backend_dev 0"
+ error_tab="0 $devsize error $backend_dev 0"
+
+ dmsetup create $devname --table "$good_tab"
+
+ mkfs -t ext4 $dev
+ mount -t ext4 -o errors=continue,strictatime $dev $mnt
+
+ dmsetup load $devname --table "$error_tab" && dmsetup resume $devname
+ echo 3 > /proc/sys/vm/drop_caches
+ ls -l $mnt
+ exit 0
+
+[ Patch changed to simplify the function a tiny bit. -- Ted ]
+
+Signed-off-by: Eryu Guan <guaneryu@gmail.com>
+Signed-off-by: Theodore Ts'o <tytso@mit.edu>
+Cc: Jan Kara <jack@suse.cz>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ fs/ext4/inode.c | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+--- a/fs/ext4/inode.c
++++ b/fs/ext4/inode.c
+@@ -4972,6 +4972,8 @@ int ext4_mark_inode_dirty(handle_t *hand
+ might_sleep();
+ trace_ext4_mark_inode_dirty(inode, _RET_IP_);
+ err = ext4_reserve_inode_write(handle, inode, &iloc);
++ if (err)
++ return err;
+ if (ext4_handle_valid(handle) &&
+ EXT4_I(inode)->i_extra_isize < sbi->s_want_extra_isize &&
+ !ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND)) {
+@@ -5002,9 +5004,7 @@ int ext4_mark_inode_dirty(handle_t *hand
+ }
+ }
+ }
+- if (!err)
+- err = ext4_mark_iloc_dirty(handle, inode, &iloc);
+- return err;
++ return ext4_mark_iloc_dirty(handle, inode, &iloc);
+ }
+
+ /*