Commit 74dae427 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o

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: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent ed8ad838
...@@ -3281,6 +3281,9 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, ...@@ -3281,6 +3281,9 @@ 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. * case, we allocate an io_end structure to hook to the iocb.
*/ */
iocb->private = NULL; iocb->private = NULL;
if (overwrite) {
get_block_func = ext4_get_block_overwrite;
} else {
ext4_inode_aio_set(inode, NULL); ext4_inode_aio_set(inode, NULL);
if (!is_sync_kiocb(iocb)) { if (!is_sync_kiocb(iocb)) {
io_end = ext4_init_io_end(inode, GFP_NOFS); io_end = ext4_init_io_end(inode, GFP_NOFS);
...@@ -3289,7 +3292,8 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, ...@@ -3289,7 +3292,8 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
goto retake_lock; goto retake_lock;
} }
/* /*
* Grab reference for DIO. Will be dropped in ext4_end_io_dio() * Grab reference for DIO. Will be dropped in
* ext4_end_io_dio()
*/ */
iocb->private = ext4_get_io_end(io_end); iocb->private = ext4_get_io_end(io_end);
/* /*
...@@ -3300,10 +3304,6 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, ...@@ -3300,10 +3304,6 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
*/ */
ext4_inode_aio_set(inode, io_end); ext4_inode_aio_set(inode, io_end);
} }
if (overwrite) {
get_block_func = ext4_get_block_overwrite;
} else {
get_block_func = ext4_get_block_write; get_block_func = ext4_get_block_write;
dio_flags = DIO_LOCKING; dio_flags = DIO_LOCKING;
} }
......
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