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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: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Shaohua Li 2017-09-01 11:15:17 -07:00 committed by Jens Axboe
parent 12cd3a2fe3
commit 92d773324b
2 changed files with 17 additions and 4 deletions
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16
drivers/block/loop.c
View File

@ -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;

3
drivers/block/loop.h
View File

@ -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;