Commit 419e9c38 authored Nov 21, 2019 by Jan Kara Committed by Darrick J. Wong Nov 22, 2019

iomap: Fix pipe page leakage during splicing



When splicing using iomap_dio_rw() to a pipe, we may leak pipe pages
because bio_iov_iter_get_pages() records that the pipe will have full
extent worth of data however if file size is not block size aligned
iomap_dio_rw() returns less than what bio_iov_iter_get_pages() set up
and splice code gets confused leaking a pipe page with the file tail.

Handle the situation similarly to the old direct IO implementation and
revert iter to actually returned read amount which makes iter consistent
with value returned from iomap_dio_rw() and thus the splice code is
happy.

Fixes: ff6a9292 ("iomap: implement direct I/O")
CC: stable@vger.kernel.org
Reported-by:  <syzbot+991400e8eba7e00a26e1@syzkaller.appspotmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

parent 6334b91e

fs/iomap/direct-io.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -502,8 +502,15 @@ iomap_dio_rw(struct kiocb iocb, struct iov_iter iter,
		}
		pos += ret;

		if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
		if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
		/*
		* We only report that we've read data up to i_size.
		* Revert iter to a state corresponding to that as
		* some callers (such as splice code) rely on it.
		*/
		iov_iter_revert(iter, pos - dio->i_size);
		break;
		}
		} while ((count = iov_iter_count(iter)) > 0);
		blk_finish_plug(&plug);

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