4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: ethanwu <[email protected]> commit 998ac6d21cfd6efd58f5edf420bae8839dda9f2a upstream. In preivous patch: Btrfs: kill trans in run_delalloc_nocow and btrfs_cross_ref_exist We avoid starting btrfs transaction and get this information from fs_info->running_transaction directly. When accessing running_transaction in check_delayed_ref, there's a chance that current transaction will be freed by commit transaction after the NULL pointer check of running_transaction is passed. After looking all the other places using fs_info->running_transaction, they are either protected by trans_lock or holding the transactions. Fix this by using trans_lock and increasing the use_count. Fixes: e4c3b2dcd144 ("Btrfs: kill trans in run_delalloc_nocow and btrfs_cross_ref_exist") CC: [email protected] # 4.14+ Signed-off-by: ethanwu <[email protected]> Signed-off-by: David Sterba <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/btrfs/extent-tree.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3171,7 +3171,11 @@ static noinline int check_delayed_ref(st struct btrfs_transaction *cur_trans; int ret = 0; + spin_lock(&root->fs_info->trans_lock); cur_trans = root->fs_info->running_transaction; + if (cur_trans) + refcount_inc(&cur_trans->use_count); + spin_unlock(&root->fs_info->trans_lock); if (!cur_trans) return 0; @@ -3180,6 +3184,7 @@ static noinline int check_delayed_ref(st head = btrfs_find_delayed_ref_head(delayed_refs, bytenr); if (!head) { spin_unlock(&delayed_refs->lock); + btrfs_put_transaction(cur_trans); return 0; } @@ -3196,6 +3201,7 @@ static noinline int check_delayed_ref(st mutex_lock(&head->mutex); mutex_unlock(&head->mutex); btrfs_put_delayed_ref(&head->node); + btrfs_put_transaction(cur_trans); return -EAGAIN; } spin_unlock(&delayed_refs->lock); @@ -3223,6 +3229,7 @@ static noinline int check_delayed_ref(st } spin_unlock(&head->lock); mutex_unlock(&head->mutex); + btrfs_put_transaction(cur_trans); return ret; }
