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 calls aio_complete() which frees the iocb
object. If that slab object gets reallocated, then ext4_end_io_dio()
can end up clearing someone else's iocb->private, this use-after-free
can cause a leak of a struct ext4_io_end_t structure.
Detected and tested with slab poisoning.
[ Note: Can also reproduce using 12 fio's against 12 file systems with the
following configuration file:
[global]
direct=1
ioengine=libaio
iodepth=1
bs=4k
ba=4k
size=128m
[create]
filename=${TESTDIR}
rw=write
-- tytso ]
Google-Bug-Id: 5354697
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Kent Overstreet <koverstreet@google.com>
Tested-by: Kent Overstreet <koverstreet@google.com>
Cc: stable@kernel.org
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index fffec40..848f436 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2807,8 +2807,8 @@
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);