loop: zero fill bio instead of return -EIO for partial read (306df071) · Commits · 戴 / test

commit ("deny partial write for loop dev fd") tried to fix the loop device partial read information leak problem. But it changed the semantics of read behavior. When we read beyond the end of the device we should get 0 bytes, which is normal behavior, we should not just return -EIO Instead of returning -EIO, zero out the bio to avoid information leak in case of partail read. Signed-off-by:

Dave Young <dyoung@redhat.com> Reviewed-by:

Jeff Moyer <jmoyer@redhat.com> Tested-by:

Jeff Moyer <jmoyer@redhat.com> Cc: Dmitry Monakhov <dmonakhov@sw.ru> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

+13 −11

Original line number	Diff line number	Diff line
		@@ -356,14 +356,14 @@ lo_direct_splice_actor(struct pipe_inode_info pipe, struct splice_desc sd)
		return __splice_from_pipe(pipe, sd, lo_splice_actor);
		}

		static int
		static ssize_t
		do_lo_receive(struct loop_device *lo,
		struct bio_vec *bvec, int bsize, loff_t pos)
		{
		struct lo_read_data cookie;
		struct splice_desc sd;
		struct file *file;
		long retval;
		ssize_t retval;

		cookie.lo = lo;
		cookie.page = bvec->bv_page;
		@@ -379,26 +379,28 @@ do_lo_receive(struct loop_device *lo,
		file = lo->lo_backing_file;
		retval = splice_direct_to_actor(file, &sd, lo_direct_splice_actor);

		if (retval < 0)
		return retval;
		if (retval != bvec->bv_len)
		return -EIO;
		return 0;
		}

		static int
		lo_receive(struct loop_device lo, struct bio bio, int bsize, loff_t pos)
		{
		struct bio_vec *bvec;
		int i, ret = 0;
		ssize_t s;
		int i;

		bio_for_each_segment(bvec, bio, i) {
		ret = do_lo_receive(lo, bvec, bsize, pos);
		if (ret < 0)
		s = do_lo_receive(lo, bvec, bsize, pos);
		if (s < 0)
		return s;

		if (s != bvec->bv_len) {
		zero_fill_bio(bio);
		break;
		}
		pos += bvec->bv_len;
		}
		return ret;
		return 0;
		}

		static int do_bio_filebacked(struct loop_device lo, struct bio bio)

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