From c404e0dc2c843b154f9a36c3aec10d0a715d88eb Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Thu, 30 Jan 2014 16:46:55 +0800 Subject: [PATCH] Btrfs: fix use-after-free in the finishing procedure of the device replace During device replace test, we hit a null pointer deference (It was very easy to reproduce it by running xfstests' btrfs/011 on the devices with the virtio scsi driver). There were two bugs that caused this problem: - We might allocate new chunks on the replaced device after we updated the mapping tree. And we forgot to replace the source device in those mapping of the new chunks. - We might get the mapping information which including the source device before the mapping information update. And then submit the bio which was based on that mapping information after we freed the source device. For the first bug, we can fix it by doing mapping tree update and source device remove in the same context of the chunk mutex. The chunk mutex is used to protect the allocable device list, the above method can avoid the new chunk allocation, and after we remove the source device, all the new chunks will be allocated on the new device. So it can fix the first bug. For the second bug, we need make sure all flighting bios are finished and no new bios are produced during we are removing the source device. To fix this problem, we introduced a global @bio_counter, we not only inc/dec @bio_counter outsize of map_blocks, but also inc it before submitting bio and dec @bio_counter when ending bios. Since Raid56 is a little different and device replace dosen't support raid56 yet, it is not addressed in the patch and I add comments to make sure we will fix it in the future. Reported-by: Qu Wenruo Signed-off-by: Wang Shilong Signed-off-by: Miao Xie Signed-off-by: Josef Bacik --- fs/btrfs/ctree.h | 9 +++++ fs/btrfs/dev-replace.c | 74 ++++++++++++++++++++++++++++++++++++++---- fs/btrfs/disk-io.c | 12 ++++++- fs/btrfs/volumes.c | 30 +++++++++++++---- fs/btrfs/volumes.h | 1 + 5 files changed, 111 insertions(+), 15 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index fceddbdfdd3d..dac6653d4cce 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -351,6 +351,7 @@ static inline unsigned long btrfs_chunk_item_size(int num_stripes) #define BTRFS_FS_STATE_ERROR 0 #define BTRFS_FS_STATE_REMOUNTING 1 #define BTRFS_FS_STATE_TRANS_ABORTED 2 +#define BTRFS_FS_STATE_DEV_REPLACING 3 /* Super block flags */ /* Errors detected */ @@ -1674,6 +1675,9 @@ struct btrfs_fs_info { atomic_t mutually_exclusive_operation_running; + struct percpu_counter bio_counter; + wait_queue_head_t replace_wait; + struct semaphore uuid_tree_rescan_sem; unsigned int update_uuid_tree_gen:1; }; @@ -4008,6 +4012,11 @@ int btrfs_scrub_cancel_dev(struct btrfs_fs_info *info, int btrfs_scrub_progress(struct btrfs_root *root, u64 devid, struct btrfs_scrub_progress *progress); +/* dev-replace.c */ +void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info); +void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info); +void btrfs_bio_counter_dec(struct btrfs_fs_info *fs_info); + /* reada.c */ struct reada_control { struct btrfs_root *root; /* tree to prefetch */ diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index b20d59e5e5dd..ec1c3f3a775d 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -431,6 +431,35 @@ int btrfs_dev_replace_start(struct btrfs_root *root, return ret; } +/* + * blocked until all flighting bios are finished. + */ +static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info) +{ + s64 writers; + DEFINE_WAIT(wait); + + set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state); + do { + prepare_to_wait(&fs_info->replace_wait, &wait, + TASK_UNINTERRUPTIBLE); + writers = percpu_counter_sum(&fs_info->bio_counter); + if (writers) + schedule(); + finish_wait(&fs_info->replace_wait, &wait); + } while (writers); +} + +/* + * we have removed target device, it is safe to allow new bios request. + */ +static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info) +{ + clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state); + if (waitqueue_active(&fs_info->replace_wait)) + wake_up(&fs_info->replace_wait); +} + static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, int scrub_ret) { @@ -458,12 +487,6 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, src_device = dev_replace->srcdev; btrfs_dev_replace_unlock(dev_replace); - /* replace old device with new one in mapping tree */ - if (!scrub_ret) - btrfs_dev_replace_update_device_in_mapping_tree(fs_info, - src_device, - tgt_device); - /* * flush all outstanding I/O and inode extent mappings before the * copy operation is declared as being finished @@ -495,7 +518,12 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, dev_replace->time_stopped = get_seconds(); dev_replace->item_needs_writeback = 1; - if (scrub_ret) { + /* replace old device with new one in mapping tree */ + if (!scrub_ret) { + btrfs_dev_replace_update_device_in_mapping_tree(fs_info, + src_device, + tgt_device); + } else { printk_in_rcu(KERN_ERR "BTRFS: btrfs_scrub_dev(%s, %llu, %s) failed %d\n", src_device->missing ? "" : @@ -534,8 +562,12 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, fs_info->fs_devices->latest_bdev = tgt_device->bdev; list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list); + btrfs_rm_dev_replace_blocked(fs_info); + btrfs_rm_dev_replace_srcdev(fs_info, src_device); + btrfs_rm_dev_replace_unblocked(fs_info); + /* * this is again a consistent state where no dev_replace procedure * is running, the target device is part of the filesystem, the @@ -865,3 +897,31 @@ void btrfs_dev_replace_unlock(struct btrfs_dev_replace *dev_replace) mutex_unlock(&dev_replace->lock_management_lock); } } + +void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info) +{ + percpu_counter_inc(&fs_info->bio_counter); +} + +void btrfs_bio_counter_dec(struct btrfs_fs_info *fs_info) +{ + percpu_counter_dec(&fs_info->bio_counter); + + if (waitqueue_active(&fs_info->replace_wait)) + wake_up(&fs_info->replace_wait); +} + +void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info) +{ + DEFINE_WAIT(wait); +again: + percpu_counter_inc(&fs_info->bio_counter); + if (test_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state)) { + btrfs_bio_counter_dec(fs_info); + wait_event(fs_info->replace_wait, + !test_bit(BTRFS_FS_STATE_DEV_REPLACING, + &fs_info->fs_state)); + goto again; + } + +} diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index fcf367581073..0cafacb07b43 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2136,10 +2136,16 @@ int open_ctree(struct super_block *sb, goto fail_dirty_metadata_bytes; } + ret = percpu_counter_init(&fs_info->bio_counter, 0); + if (ret) { + err = ret; + goto fail_delalloc_bytes; + } + fs_info->btree_inode = new_inode(sb); if (!fs_info->btree_inode) { err = -ENOMEM; - goto fail_delalloc_bytes; + goto fail_bio_counter; } mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS); @@ -2214,6 +2220,7 @@ int open_ctree(struct super_block *sb, atomic_set(&fs_info->scrub_pause_req, 0); atomic_set(&fs_info->scrubs_paused, 0); atomic_set(&fs_info->scrub_cancel_req, 0); + init_waitqueue_head(&fs_info->replace_wait); init_waitqueue_head(&fs_info->scrub_pause_wait); fs_info->scrub_workers_refcnt = 0; #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY @@ -2966,6 +2973,8 @@ int open_ctree(struct super_block *sb, btrfs_mapping_tree_free(&fs_info->mapping_tree); iput(fs_info->btree_inode); +fail_bio_counter: + percpu_counter_destroy(&fs_info->bio_counter); fail_delalloc_bytes: percpu_counter_destroy(&fs_info->delalloc_bytes); fail_dirty_metadata_bytes: @@ -3613,6 +3622,7 @@ int close_ctree(struct btrfs_root *root) percpu_counter_destroy(&fs_info->dirty_metadata_bytes); percpu_counter_destroy(&fs_info->delalloc_bytes); + percpu_counter_destroy(&fs_info->bio_counter); bdi_destroy(&fs_info->bdi); cleanup_srcu_struct(&fs_info->subvol_srcu); diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index b68afe32419f..07629e99809a 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5263,6 +5263,7 @@ int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree, static void btrfs_end_bio(struct bio *bio, int err) { struct btrfs_bio *bbio = bio->bi_private; + struct btrfs_device *dev = bbio->stripes[0].dev; int is_orig_bio = 0; if (err) { @@ -5270,7 +5271,6 @@ static void btrfs_end_bio(struct bio *bio, int err) if (err == -EIO || err == -EREMOTEIO) { unsigned int stripe_index = btrfs_io_bio(bio)->stripe_index; - struct btrfs_device *dev; BUG_ON(stripe_index >= bbio->num_stripes); dev = bbio->stripes[stripe_index].dev; @@ -5292,6 +5292,8 @@ static void btrfs_end_bio(struct bio *bio, int err) if (bio == bbio->orig_bio) is_orig_bio = 1; + btrfs_bio_counter_dec(bbio->fs_info); + if (atomic_dec_and_test(&bbio->stripes_pending)) { if (!is_orig_bio) { bio_put(bio); @@ -5440,6 +5442,9 @@ static void submit_stripe_bio(struct btrfs_root *root, struct btrfs_bio *bbio, } #endif bio->bi_bdev = dev->bdev; + + btrfs_bio_counter_inc_noblocked(root->fs_info); + if (async) btrfs_schedule_bio(root, dev, rw, bio); else @@ -5508,28 +5513,38 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio, length = bio->bi_size; map_length = length; + btrfs_bio_counter_inc_blocked(root->fs_info); ret = __btrfs_map_block(root->fs_info, rw, logical, &map_length, &bbio, mirror_num, &raid_map); - if (ret) /* -ENOMEM */ + if (ret) { + btrfs_bio_counter_dec(root->fs_info); return ret; + } total_devs = bbio->num_stripes; bbio->orig_bio = first_bio; bbio->private = first_bio->bi_private; bbio->end_io = first_bio->bi_end_io; + bbio->fs_info = root->fs_info; atomic_set(&bbio->stripes_pending, bbio->num_stripes); if (raid_map) { /* In this case, map_length has been set to the length of a single stripe; not the whole write */ if (rw & WRITE) { - return raid56_parity_write(root, bio, bbio, - raid_map, map_length); + ret = raid56_parity_write(root, bio, bbio, + raid_map, map_length); } else { - return raid56_parity_recover(root, bio, bbio, - raid_map, map_length, - mirror_num); + ret = raid56_parity_recover(root, bio, bbio, + raid_map, map_length, + mirror_num); } + /* + * FIXME, replace dosen't support raid56 yet, please fix + * it in the future. + */ + btrfs_bio_counter_dec(root->fs_info); + return ret; } if (map_length < length) { @@ -5571,6 +5586,7 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio, async_submit); dev_nr++; } + btrfs_bio_counter_dec(root->fs_info); return 0; } diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 8b3cd142b373..80754f9dd3df 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -192,6 +192,7 @@ typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err); struct btrfs_bio { atomic_t stripes_pending; + struct btrfs_fs_info *fs_info; bio_end_io_t *end_io; struct bio *orig_bio; void *private; -- GitLab