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author | Jan Kara <jack@suse.cz> | 2016-02-19 00:33:21 -0500 |
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committer | Sasha Levin <sasha.levin@oracle.com> | 2016-03-04 10:25:45 -0500 |
commit | 62adae8f26b918f4403129e355d81301a629b6a2 (patch) | |
tree | 4e1e6a5ef2e1182cc9ad586b85b3f8cd01e3c1de /fs | |
parent | 5d0e8394db90caa6d06477f68cbdb48fe65f468d (diff) | |
download | lwn-62adae8f26b918f4403129e355d81301a629b6a2.tar.gz lwn-62adae8f26b918f4403129e355d81301a629b6a2.zip |
ext4: fix crashes in dioread_nolock mode
[ Upstream commit 74dae4278546b897eb81784fdfcce872ddd8b2b8 ]
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: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/ext4/inode.c | 40 |
1 files changed, 20 insertions, 20 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 966c614822cc..2b3a53a51582 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3133,29 +3133,29 @@ 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; } |