From: Qu Wenruo wqu@suse.com
commit 10995c0491204c861948c9850939a7f4e90760a4 upstream.
Commit d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots()") expands the life span of root->reloc_root.
This breaks certain checs of fs_info->reloc_ctl. Before that commit, if we have a root with valid reloc_root, then it's ensured to have fs_info->reloc_ctl.
But now since reloc_root doesn't always mean a valid fs_info->reloc_ctl, such check is unreliable and can cause the following NULL pointer dereference:
BUG: unable to handle kernel NULL pointer dereference at 00000000000005c1 IP: btrfs_reloc_pre_snapshot+0x20/0x50 [btrfs] PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 0 PID: 10379 Comm: snapperd Not tainted Call Trace: create_pending_snapshot+0xd7/0xfc0 [btrfs] create_pending_snapshots+0x8e/0xb0 [btrfs] btrfs_commit_transaction+0x2ac/0x8f0 [btrfs] btrfs_mksubvol+0x561/0x570 [btrfs] btrfs_ioctl_snap_create_transid+0x189/0x190 [btrfs] btrfs_ioctl_snap_create_v2+0x102/0x150 [btrfs] btrfs_ioctl+0x5c9/0x1e60 [btrfs] do_vfs_ioctl+0x90/0x5f0 SyS_ioctl+0x74/0x80 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x7fd7cdab8467
Fix it by explicitly checking fs_info->reloc_ctl other than using the implied root->reloc_root.
Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") Signed-off-by: Qu Wenruo wqu@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/relocation.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
--- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -4667,14 +4667,12 @@ int btrfs_reloc_cow_block(struct btrfs_t void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending, u64 *bytes_to_reserve) { - struct btrfs_root *root; - struct reloc_control *rc; + struct btrfs_root *root = pending->root; + struct reloc_control *rc = root->fs_info->reloc_ctl;
- root = pending->root; - if (!root->reloc_root) + if (!root->reloc_root || !rc) return;
- rc = root->fs_info->reloc_ctl; if (!rc->merge_reloc_tree) return;
@@ -4703,10 +4701,10 @@ int btrfs_reloc_post_snapshot(struct btr struct btrfs_root *root = pending->root; struct btrfs_root *reloc_root; struct btrfs_root *new_root; - struct reloc_control *rc; + struct reloc_control *rc = root->fs_info->reloc_ctl; int ret;
- if (!root->reloc_root) + if (!root->reloc_root || !rc) return 0;
rc = root->fs_info->reloc_ctl;