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ext4: fix ext4_end_io_dio() racing against fsync() 

We need to make sure iocb->private is cleared *before* we put the
io_end structure on i_completed_io_list.  Otherwise fsync() could
potentially run on another CPU and free the iocb structure out from
under us.

Reported-by: Kent Overstreet <koverstreet@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Theodore Ts'o 2011-12-12 10:53:02 -05:00
parent dc47ce90c3
commit b5a7e97039
1 changed files with 2 additions and 2 deletions
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4
fs/ext4/inode.c
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@ -2781,10 +2781,11 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
iocb->private, io_end->inode->i_ino, iocb, offset,
size);
iocb->private = NULL;
/* if not aio dio with unwritten extents, just free io and return */
if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
ext4_free_io_end(io_end);
iocb->private = NULL;
out:
if (is_async)
aio_complete(iocb, ret, 0);
@ -2807,7 +2808,6 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
/* queue the work to convert unwritten extents to written */
iocb->private = NULL;
queue_work(wq, &io_end->work);
/* XXX: probably should move into the real I/O completion handler */