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Commit 95d78c28 authored by Vitaly Mayatskikh's avatar Vitaly Mayatskikh Committed by Al Viro
Browse files

fix unbalanced page refcounting in bio_map_user_iov 



bio_map_user_iov and bio_unmap_user do unbalanced pages refcounting if
IO vector has small consecutive buffers belonging to the same page.
bio_add_pc_page merges them into one, but the page reference is never
dropped.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarVitaly Mayatskikh <v.mayatskih@gmail.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 899f0429

block/bio.c

+8 −0
Original line number Original line Diff line number Diff line
@@ -1383,6 +1383,7 @@ struct bio *bio_map_user_iov(struct request_queue *q, 
		offset = offset_in_page(uaddr);

		offset = offset_in_page(uaddr);

		for (j = cur_page; j < page_limit; j++) {

		for (j = cur_page; j < page_limit; j++) {

			unsigned int bytes = PAGE_SIZE - offset;

			unsigned int bytes = PAGE_SIZE - offset;

			unsigned short prev_bi_vcnt = bio->bi_vcnt;





			if (len <= 0)

			if (len <= 0)

				break;

				break;
@@ -1397,6 +1398,13 @@ struct bio *bio_map_user_iov(struct request_queue *q, 
					    bytes)

					    bytes)

				break;

				break;





			/*

			 * check if vector was merged with previous

			 * drop page reference if needed

			 */

			if (bio->bi_vcnt == prev_bi_vcnt)

				put_page(pages[j]);



			len -= bytes;

			len -= bytes;

			offset = 0;

			offset = 0;

		}

		}