3.2.80-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eryu Guan <guaneryu@xxxxxxxxx> 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@xxxxxxxxx> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- fs/ext4/inode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4636,6 +4636,8 @@ 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)) { @@ -4666,9 +4668,7 @@ 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); } /* -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html