From 01da30a885baa667801facc2a54c80346ab6c414 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 24 Nov 2011 19:22:24 -0500 Subject: [PATCH] ext4: fix racy use-after-free in ext4_end_io_dio() commit 4c81f045c0bd2cbb78cc6446a4cd98038fe11a2e upstream. 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 Signed-off-by: "Theodore Ts'o" Reported-by: Kent Overstreet Tested-by: Kent Overstreet Signed-off-by: Greg Kroah-Hartman --- 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 89c47f4ee00..b644b9c164a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2656,8 +2656,8 @@ 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 */ - 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);