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block: fix use after free in __blkdev_direct_IO 

We can't dereference the dio structure after submitting the last bio for
this request, as I/O completion might have happened before the code is
run. Introduce a local is_sync variable instead.

Fixes: 542ff7bf ("block: new direct I/O implementation")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Matias Bjørling <m@bjorling.me>
Tested-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig 2017-01-24 14:50:19 +01:00 committed by Jens Axboe
parent a4685d2f58
commit 690e5325b8
1 changed files with 3 additions and 3 deletions
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6
fs/block_dev.c
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@ -331,7 +331,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
struct blk_plug plug;
struct blkdev_dio *dio;
struct bio *bio;
bool is_read = (iov_iter_rw(iter) == READ);
bool is_read = (iov_iter_rw(iter) == READ), is_sync;
loff_t pos = iocb->ki_pos;
blk_qc_t qc = BLK_QC_T_NONE;
int ret;
@ -344,7 +344,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
bio_get(bio); /* extra ref for the completion handler */
dio = container_of(bio, struct blkdev_dio, bio);
dio->is_sync = is_sync_kiocb(iocb);
dio->is_sync = is_sync = is_sync_kiocb(iocb);
if (dio->is_sync)
dio->waiter = current;
else
@ -398,7 +398,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
}
blk_finish_plug(&plug);
if (!dio->is_sync)
if (!is_sync)
return -EIOCBQUEUED;
for (;;) {