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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: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2017-03-29 09:33:22 +08:00 committed by David Sterba
parent ae6529c35b
commit e501bfe323
1 changed files with 9 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
fs/btrfs/scrub.c
View File

@ -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++;