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Commit 92d77332 authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

block/loop: fix use after free 



lo_rw_aio->call_read_iter->
1       aops->direct_IO
2       iov_iter_revert
lo_rw_aio_complete could happen between 1 and 2, the bio and bvec could
be freed before 2, which accesses bvec.

Signed-off-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 12cd3a2f

drivers/block/loop.c

+13 −3
Original line number Diff line number Diff line
@@ -463,14 +463,21 @@ static void lo_complete_rq(struct request *rq) 
	blk_mq_end_request(rq, cmd->ret < 0 ? BLK_STS_IOERR : BLK_STS_OK);

}



static void lo_rw_aio_do_completion(struct loop_cmd *cmd)

{

	if (!atomic_dec_and_test(&cmd->ref))

		return;

	kfree(cmd->bvec);

	cmd->bvec = NULL;

	blk_mq_complete_request(cmd->rq);

}



static void lo_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)

{

	struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb);



	kfree(cmd->bvec);

	cmd->bvec = NULL;

	cmd->ret = ret;

	blk_mq_complete_request(cmd->rq);

	lo_rw_aio_do_completion(cmd);

}



static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
@@ -518,6 +525,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, 
		bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);

		segments = bio_segments(bio);

	}

	atomic_set(&cmd->ref, 2);



	iov_iter_bvec(&iter, ITER_BVEC | rw, bvec,

		      segments, blk_rq_bytes(rq));
@@ -533,6 +541,8 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, 
	else

		ret = call_read_iter(file, &cmd->iocb, &iter);



	lo_rw_aio_do_completion(cmd);



	if (ret != -EIOCBQUEUED)

		cmd->iocb.ki_complete(&cmd->iocb, ret, 0);

	return 0;

drivers/block/loop.h

+4 −1
Original line number Diff line number Diff line
@@ -68,7 +68,10 @@ struct loop_cmd { 
	struct kthread_work work;

	struct request *rq;

	struct list_head list;

	union {

		bool use_aio; /* use AIO interface to handle I/O */

		atomic_t ref; /* only for aio */

	};

	long ret;

	struct kiocb iocb;

	struct bio_vec *bvec;