Commit e501bfe3 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: Prevent scrub recheck from racing with dev replace 



scrub_setup_recheck_block() calls btrfs_map_sblock() and then accesses
bbio without protection of bio_counter.

This can lead to use-after-free if racing with dev replace cancel.

Fix it by increasing bio_counter before calling btrfs_map_sblock() and
decreasing the bio_counter when corresponding recover is finished.

Cc: Liu Bo <bo.li.liu@oracle.com>
Reported-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: default avatarQu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent ae6529c3

fs/btrfs/scrub.c

+9 −4
Original line number Diff line number Diff line
@@ -860,9 +860,11 @@ static inline void scrub_get_recover(struct scrub_recover *recover) 
	refcount_inc(&recover->refs);

}



static inline void scrub_put_recover(struct scrub_recover *recover)

static inline void scrub_put_recover(struct btrfs_fs_info *fs_info,

				     struct scrub_recover *recover)

{

	if (refcount_dec_and_test(&recover->refs)) {

		btrfs_bio_counter_dec(fs_info);

		btrfs_put_bbio(recover->bbio);

		kfree(recover);

	}
@@ -1241,7 +1243,7 @@ out: 
				sblock->pagev[page_index]->sblock = NULL;

				recover = sblock->pagev[page_index]->recover;

				if (recover) {

					scrub_put_recover(recover);

					scrub_put_recover(fs_info, recover);

					sblock->pagev[page_index]->recover =

									NULL;

				}
@@ -1330,16 +1332,19 @@ static int scrub_setup_recheck_block(struct scrub_block *original_sblock, 
		 * with a length of PAGE_SIZE, each returned stripe

		 * represents one mirror

		 */

		btrfs_bio_counter_inc_blocked(fs_info);

		ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS,

				logical, &mapped_length, &bbio);

		if (ret || !bbio || mapped_length < sublen) {

			btrfs_put_bbio(bbio);

			btrfs_bio_counter_dec(fs_info);

			return -EIO;

		}



		recover = kzalloc(sizeof(struct scrub_recover), GFP_NOFS);

		if (!recover) {

			btrfs_put_bbio(bbio);

			btrfs_bio_counter_dec(fs_info);

			return -ENOMEM;

		}
@@ -1365,7 +1370,7 @@ leave_nomem: 
				spin_lock(&sctx->stat_lock);

				sctx->stat.malloc_errors++;

				spin_unlock(&sctx->stat_lock);

				scrub_put_recover(recover);

				scrub_put_recover(fs_info, recover);

				return -ENOMEM;

			}

			scrub_page_get(page);
@@ -1407,7 +1412,7 @@ leave_nomem: 
			scrub_get_recover(recover);

			page->recover = recover;

		}

		scrub_put_recover(recover);

		scrub_put_recover(fs_info, recover);

		length -= sublen;

		logical += sublen;

		page_index++;

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