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Subject[PATCH] ext4: fix racy use-after-free in ext4_end_io_dio()
ext4_end_io_dio() queues io_end->work and then clears iocb->private;
however, io_end->work completes the iocb by calling aio_complete(),
which may happen before io_end->work clearing thus leading to
use-after-free.

Detected and tested with slab poisoning.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Kent Overstreet <koverstreet@google.com>
Tested-by: Kent Overstreet <koverstreet@google.com>
Cc: stable@kernel.org
---
I *think* this is the corret fix but am not too familiar with code
path, so please proceed with caution.
Thank you.

fs/ext4/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 240f6e2..0f5583b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2806,8 +2806,8 @@ out:
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

/* queue the work to convert unwritten extents to written */
- queue_work(wq, &io_end->work);
iocb->private = NULL;
+ queue_work(wq, &io_end->work);

/* XXX: probably should move into the real I/O completion handler */
inode_dio_done(inode);

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