[3/3] btrfs: relocation: Fix a KASAN report on btrfs_reloc_pre_snapshot() due to extended reloc root lifespan
diff mbox series

Message ID 20191211050004.18414-4-wqu@suse.com
State New
Headers show
Series
  • btrfs: fixes for relocation to avoid KASAN reports
Related show

Commit Message

Qu Wenruo Dec. 11, 2019, 5 a.m. UTC
[BUG]
When running workload with balance start/cancel, snapshot
creation/deletion and fsstress, we can hit the following KASAN report:
  ==================================================================
  BUG: KASAN: use-after-free in btrfs_reloc_pre_snapshot+0x85/0xc0 [btrfs]
  Read of size 4 at addr ffff888157140100 by task btrfs/1822

  CPU: 2 PID: 1822 Comm: btrfs Tainted: G           O      5.5.0-rc1-custom+ #40
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
  Call Trace:
   dump_stack+0xc2/0x11a
   print_address_description.constprop.0+0x20/0x210
   __kasan_report.cold+0x1b/0x41
   kasan_report+0x12/0x20
   check_memory_region+0x13c/0x1b0
   __asan_loadN+0xf/0x20
   btrfs_reloc_pre_snapshot+0x85/0xc0 [btrfs]
   create_pending_snapshot+0x209/0x15f0 [btrfs]
   create_pending_snapshots+0x111/0x140 [btrfs]
   btrfs_commit_transaction+0x7a6/0x1360 [btrfs]
   btrfs_mksubvol+0x915/0x960 [btrfs]
   btrfs_ioctl_snap_create_transid+0x1d5/0x1e0 [btrfs]
   btrfs_ioctl_snap_create_v2+0x1d3/0x270 [btrfs]
   btrfs_ioctl+0x241b/0x3e60 [btrfs]
   do_vfs_ioctl+0x831/0xb10
   ksys_ioctl+0x67/0x90
   __x64_sys_ioctl+0x43/0x50
   do_syscall_64+0x79/0xe0
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

[CAUSE]
Again, we try to access root->reloc_root without verify if that reloc
root is already dead (being freed).

[FIX]
Check if the root has dead reloc root before accessing it.

Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots")
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/relocation.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Josef Bacik Dec. 11, 2019, 2:55 p.m. UTC | #1
On 12/11/19 12:00 AM, Qu Wenruo wrote:
> [BUG]
> When running workload with balance start/cancel, snapshot
> creation/deletion and fsstress, we can hit the following KASAN report:
>    ==================================================================
>    BUG: KASAN: use-after-free in btrfs_reloc_pre_snapshot+0x85/0xc0 [btrfs]
>    Read of size 4 at addr ffff888157140100 by task btrfs/1822
> 
>    CPU: 2 PID: 1822 Comm: btrfs Tainted: G           O      5.5.0-rc1-custom+ #40
>    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
>    Call Trace:
>     dump_stack+0xc2/0x11a
>     print_address_description.constprop.0+0x20/0x210
>     __kasan_report.cold+0x1b/0x41
>     kasan_report+0x12/0x20
>     check_memory_region+0x13c/0x1b0
>     __asan_loadN+0xf/0x20
>     btrfs_reloc_pre_snapshot+0x85/0xc0 [btrfs]
>     create_pending_snapshot+0x209/0x15f0 [btrfs]
>     create_pending_snapshots+0x111/0x140 [btrfs]
>     btrfs_commit_transaction+0x7a6/0x1360 [btrfs]
>     btrfs_mksubvol+0x915/0x960 [btrfs]
>     btrfs_ioctl_snap_create_transid+0x1d5/0x1e0 [btrfs]
>     btrfs_ioctl_snap_create_v2+0x1d3/0x270 [btrfs]
>     btrfs_ioctl+0x241b/0x3e60 [btrfs]
>     do_vfs_ioctl+0x831/0xb10
>     ksys_ioctl+0x67/0x90
>     __x64_sys_ioctl+0x43/0x50
>     do_syscall_64+0x79/0xe0
>     entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> [CAUSE]
> Again, we try to access root->reloc_root without verify if that reloc
> root is already dead (being freed).
> 
> [FIX]
> Check if the root has dead reloc root before accessing it.
> 
> Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
> Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots")
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>   fs/btrfs/relocation.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 619ccb183515..2d2cd1596ec9 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -4721,7 +4721,8 @@ void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
>   	struct btrfs_root *root = pending->root;
>   	struct reloc_control *rc = root->fs_info->reloc_ctl;
>   
> -	if (!root->reloc_root || !rc)
> +	if (!root->reloc_root || !rc || test_bit(BTRFS_ROOT_DEAD_RELOC_TREE,
> +				&root->state))
>   		return;
>  

Same comment here as the other one, you can add

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Once it's fixed.  Thanks,

Josef

Patch
diff mbox series

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 619ccb183515..2d2cd1596ec9 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4721,7 +4721,8 @@  void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
 	struct btrfs_root *root = pending->root;
 	struct reloc_control *rc = root->fs_info->reloc_ctl;
 
-	if (!root->reloc_root || !rc)
+	if (!root->reloc_root || !rc || test_bit(BTRFS_ROOT_DEAD_RELOC_TREE,
+				&root->state))
 		return;
 
 	if (!rc->merge_reloc_tree)