From: Filipe Manana Date: Wed, 8 May 2024 10:51:07 +0000 (+0100) Subject: btrfs: zoned: fix use-after-free due to race with dev replace X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0090d6e1b210551e63cf43958dc7a1ec942cdde9;p=linux.git btrfs: zoned: fix use-after-free due to race with dev replace While loading a zone's info during creation of a block group, we can race with a device replace operation and then trigger a use-after-free on the device that was just replaced (source device of the replace operation). This happens because at btrfs_load_zone_info() we extract a device from the chunk map into a local variable and then use the device while not under the protection of the device replace rwsem. So if there's a device replace operation happening when we extract the device and that device is the source of the replace operation, we will trigger a use-after-free if before we finish using the device the replace operation finishes and frees the device. Fix this by enlarging the critical section under the protection of the device replace rwsem so that all uses of the device are done inside the critical section. CC: stable@vger.kernel.org # 6.1.x: 15c12fcc50a1: btrfs: zoned: introduce a zone_info struct in btrfs_load_block_group_zone_info CC: stable@vger.kernel.org # 6.1.x: 09a46725cc84: btrfs: zoned: factor out per-zone logic from btrfs_load_block_group_zone_info CC: stable@vger.kernel.org # 6.1.x: 9e0e3e74dc69: btrfs: zoned: factor out single bg handling from btrfs_load_block_group_zone_info CC: stable@vger.kernel.org # 6.1.x: 87463f7e0250: btrfs: zoned: factor out DUP bg handling from btrfs_load_block_group_zone_info CC: stable@vger.kernel.org # 6.1.x Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c index 4cba80b34387c..459514da16601 100644 --- a/fs/btrfs/zoned.c +++ b/fs/btrfs/zoned.c @@ -1290,7 +1290,7 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx, struct btrfs_chunk_map *map) { struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace; - struct btrfs_device *device = map->stripes[zone_idx].dev; + struct btrfs_device *device; int dev_replace_is_ongoing = 0; unsigned int nofs_flag; struct blk_zone zone; @@ -1298,7 +1298,11 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx, info->physical = map->stripes[zone_idx].physical; + down_read(&dev_replace->rwsem); + device = map->stripes[zone_idx].dev; + if (!device->bdev) { + up_read(&dev_replace->rwsem); info->alloc_offset = WP_MISSING_DEV; return 0; } @@ -1308,6 +1312,7 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx, __set_bit(zone_idx, active); if (!btrfs_dev_is_sequential(device, info->physical)) { + up_read(&dev_replace->rwsem); info->alloc_offset = WP_CONVENTIONAL; return 0; } @@ -1315,11 +1320,9 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx, /* This zone will be used for allocation, so mark this zone non-empty. */ btrfs_dev_clear_zone_empty(device, info->physical); - down_read(&dev_replace->rwsem); dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace); if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL) btrfs_dev_clear_zone_empty(dev_replace->tgtdev, info->physical); - up_read(&dev_replace->rwsem); /* * The group is mapped to a sequential zone. Get the zone write pointer @@ -1330,6 +1333,7 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx, ret = btrfs_get_dev_zone(device, info->physical, &zone); memalloc_nofs_restore(nofs_flag); if (ret) { + up_read(&dev_replace->rwsem); if (ret != -EIO && ret != -EOPNOTSUPP) return ret; info->alloc_offset = WP_MISSING_DEV; @@ -1341,6 +1345,7 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx, "zoned: unexpected conventional zone %llu on device %s (devid %llu)", zone.start << SECTOR_SHIFT, rcu_str_deref(device->name), device->devid); + up_read(&dev_replace->rwsem); return -EIO; } @@ -1368,6 +1373,8 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx, break; } + up_read(&dev_replace->rwsem); + return 0; }