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authorJan Kara <jack@suse.cz>2016-02-19 00:33:21 -0500
committerTheodore Ts'o <tytso@mit.edu>2016-02-19 00:33:21 -0500
commit74dae4278546b897eb81784fdfcce872ddd8b2b8 (patch)
tree1f8933f3ec2715cdfcbac993cf0409e884caf11c
parented8ad83808f009ade97ebbf6519bc3a97fefbc0c (diff)
ext4: fix crashes in dioread_nolock mode
Competing overwrite DIO in dioread_nolock mode will just overwrite pointer to io_end in the inode. This may result in data corruption or extent conversion happening from IO completion interrupt because we don't properly set buffer_defer_completion() when unlocked DIO races with locked DIO to unwritten extent. Since unlocked DIO doesn't need io_end for anything, just avoid allocating it and corrupting pointer from inode for locked DIO. A cleaner fix would be to avoid these games with io_end pointer from the inode but that requires more intrusive changes so we leave that for later. Cc: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
-rw-r--r--fs/ext4/inode.c40
1 files changed, 20 insertions, 20 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d6674479269d..9cc57c3b4661 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3281,29 +3281,29 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
* case, we allocate an io_end structure to hook to the iocb.
*/
iocb->private = NULL;
- ext4_inode_aio_set(inode, NULL);
- if (!is_sync_kiocb(iocb)) {
- io_end = ext4_init_io_end(inode, GFP_NOFS);
- if (!io_end) {
- ret = -ENOMEM;
- goto retake_lock;
- }
- /*
- * Grab reference for DIO. Will be dropped in ext4_end_io_dio()
- */
- iocb->private = ext4_get_io_end(io_end);
- /*
- * we save the io structure for current async direct
- * IO, so that later ext4_map_blocks() could flag the
- * io structure whether there is a unwritten extents
- * needs to be converted when IO is completed.
- */
- ext4_inode_aio_set(inode, io_end);
- }
-
if (overwrite) {
get_block_func = ext4_get_block_overwrite;
} else {
+ ext4_inode_aio_set(inode, NULL);
+ if (!is_sync_kiocb(iocb)) {
+ io_end = ext4_init_io_end(inode, GFP_NOFS);
+ if (!io_end) {
+ ret = -ENOMEM;
+ goto retake_lock;
+ }
+ /*
+ * Grab reference for DIO. Will be dropped in
+ * ext4_end_io_dio()
+ */
+ iocb->private = ext4_get_io_end(io_end);
+ /*
+ * we save the io structure for current async direct
+ * IO, so that later ext4_map_blocks() could flag the
+ * io structure whether there is a unwritten extents
+ * needs to be converted when IO is completed.
+ */
+ ext4_inode_aio_set(inode, io_end);
+ }
get_block_func = ext4_get_block_write;
dio_flags = DIO_LOCKING;
}