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authorQu Wenruo <wqu@suse.com>2019-03-18 10:48:19 +0800
committerDavid Sterba <dsterba@suse.com>2019-04-29 19:02:22 +0200
commit10995c0491204c861948c9850939a7f4e90760a4 (patch)
treed24eb353284bfd9dbac81b41d4317e57298717ca /fs/btrfs/relocation.c
parentd51f51bb6f3c11f3ee4120c35de8e6547ed493fc (diff)
downloadlinux-10995c0491204c861948c9850939a7f4e90760a4.tar.bz2
btrfs: reloc: Fix NULL pointer dereference due to expanded reloc_root lifespan
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>
Diffstat (limited to 'fs/btrfs/relocation.c')
-rw-r--r--fs/btrfs/relocation.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index b52fb99646dc..1af2bdf5c877 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4668,14 +4668,12 @@ int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
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;
@@ -4704,10 +4702,10 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
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;