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

fs/ext4/inode.c

+20 −20
Original line number Original line Diff line number Diff line
@@ -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, 
				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, 
			 */

			 */

			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;

	}

	}