From: Nathan Chancellor <natechancellor@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, stable@vger.kernel.org
Cc: Jan Kara <jack@suse.cz>, Theodore Ts'o <tytso@mit.edu>,
Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH 4.4 1/2] ext4: fix crashes in dioread_nolock mode
Date: Sun, 22 Apr 2018 01:11:31 -0700 [thread overview]
Message-ID: <20180422081132.23277-1-natechancellor@gmail.com> (raw)
From: Jan Kara <jack@suse.cz>
commit 74dae4278546b897eb81784fdfcce872ddd8b2b8 upstream.
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>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
fs/ext4/inode.c | 40 ++++++++++++++++++++--------------------
1 file changed, 20 insertions(+), 20 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f0cabc8c96cb..fa99cae9552b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3256,29 +3256,29 @@ 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_write_nolock;
} 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;
}
--
2.17.0
next reply other threads:[~2018-04-22 8:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-22 8:11 Nathan Chancellor [this message]
2018-04-22 8:11 ` [PATCH 4.4 2/2] ext4: fix deadlock between inline_data and ext4_expand_extra_isize_ea() Nathan Chancellor
2018-04-22 9:01 ` [PATCH 4.4 1/2] ext4: fix crashes in dioread_nolock mode Greg Kroah-Hartman
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