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>
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@ -3281,29 +3281,29 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
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* case, we allocate an io_end structure to hook to the iocb.
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*/
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iocb->private = NULL;
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ext4_inode_aio_set(inode, NULL);
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if (!is_sync_kiocb(iocb)) {
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io_end = ext4_init_io_end(inode, GFP_NOFS);
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if (!io_end) {
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ret = -ENOMEM;
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goto retake_lock;
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}
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/*
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* Grab reference for DIO. Will be dropped in ext4_end_io_dio()
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*/
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iocb->private = ext4_get_io_end(io_end);
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/*
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* we save the io structure for current async direct
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* IO, so that later ext4_map_blocks() could flag the
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* io structure whether there is a unwritten extents
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* needs to be converted when IO is completed.
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*/
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ext4_inode_aio_set(inode, io_end);
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}
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if (overwrite) {
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get_block_func = ext4_get_block_overwrite;
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} else {
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ext4_inode_aio_set(inode, NULL);
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if (!is_sync_kiocb(iocb)) {
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io_end = ext4_init_io_end(inode, GFP_NOFS);
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if (!io_end) {
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ret = -ENOMEM;
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goto retake_lock;
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}
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/*
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* Grab reference for DIO. Will be dropped in
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* ext4_end_io_dio()
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*/
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iocb->private = ext4_get_io_end(io_end);
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/*
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* we save the io structure for current async direct
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* IO, so that later ext4_map_blocks() could flag the
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* io structure whether there is a unwritten extents
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* needs to be converted when IO is completed.
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*/
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ext4_inode_aio_set(inode, io_end);
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}
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get_block_func = ext4_get_block_write;
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dio_flags = DIO_LOCKING;
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}
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