CVE-2023-53339

Summary

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix BUG_ON condition in btrfs_cancel_balance

Pausing and canceling balance can race to interrupt balance lead to BUG_ON panic in btrfs_cancel_balance. The BUG_ON condition in btrfs_cancel_balance does not take this race scenario into account.

However, the race condition has no other side effects. We can fix that.

Reproducing it with panic trace like this:

kernel BUG at fs/btrfs/volumes.c:4618! RIP: 0010:btrfs_cancel_balance+0x5cf/0x6a0 Call Trace: <TASK> ? do_nanosleep+0x60/0x120 ? hrtimer_nanosleep+0xb7/0x1a0 ? sched_core_clone_cookie+0x70/0x70 btrfs_ioctl_balance_ctl+0x55/0x70 btrfs_ioctl+0xa46/0xd20 __x64_sys_ioctl+0x7d/0xa0 do_syscall_64+0x38/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Race scenario as follows: > mutex_unlock(&fs_info->balance_mutex); > ——————– > …….issue pause and cancel req in another thread > ——————– > ret = __btrfs_balance(fs_info); > > mutex_lock(&fs_info->balance_mutex); > if (ret == -ECANCELED && atomic_read(&fs_info->balance_pause_req)) { > btrfs_info(fs_info, "balance: paused"); > btrfs_exclop_balance(fs_info, BTRFS_EXCLOP_BALANCE_PAUSED); > }

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/ceb9ba8e30833a4823e2dc73f80ebcdf2498d01a
• https://git.kernel.org/stable/c/ae81329f7de3aa6f34ecdfa5412e72161a30e9ce
• https://git.kernel.org/stable/c/29eefa6d0d07e185f7bfe9576f91e6dba98189c2

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