CVE-2023-54080: 
Linux Ubuntu vulnerability analysis and mitigation

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

btrfs: zoned: skip splitting and logical rewriting on pre-alloc write

When doing a relocation, there is a chance that at the time of btrfs_reloc_clone_csums(), there is no checksum for the corresponding region.

In this case, btrfs_finish_ordered_zoned()'s sum points to an invalid item and so ordered_extent's logical is set to some invalid value. Then, btrfs_lookup_block_group() in btrfs_zone_finish_endio() failed to find a block group and will hit an assert or a null pointer dereference as following.

This can be reprodcued by running btrfs/028 several times (e.g, 4 to 16 times) with a null_blk setup. The device's zone size and capacity is set to 32 MB and the storage size is set to 5 GB on my setup.

KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f]
CPU: 6 PID: 3105720 Comm: kworker/u16:13 Tainted: G        W          6.5.0-rc6-kts+ #1
Hardware name: Supermicro Super Server/X10SRL-F, BIOS 2.0 12/17/2015
Workqueue: btrfs-endio-write btrfs_work_helper [btrfs]
RIP: 0010:btrfs_zone_finish_endio.part.0+0x34/0x160 [btrfs]
Code: 41 54 49 89 fc 55 48 89 f5 53 e8 57 7d fc ff 48 8d b8 88 00 00 00 48 89 c3 48 b8 00 00 00 00 00
> 3c 02 00 0f 85 02 01 00 00 f6 83 88 00 00 00 01 0f 84 a8 00 00
RSP: 0018:ffff88833cf87b08 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000011 RSI: 0000000000000004 RDI: 0000000000000088
RBP: 0000000000000002 R08: 0000000000000001 R09: ffffed102877b827
R10: ffff888143bdc13b R11: ffff888125b1cbc0 R12: ffff888143bdc000
R13: 0000000000007000 R14: ffff888125b1cba8 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88881e500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3ed85223d5 CR3: 00000001519b4005 CR4: 00000000001706e0
Call Trace:
 <TASK>
 ? die_addr+0x3c/0xa0
 ? exc_general_protection+0x148/0x220
 ? asm_exc_general_protection+0x22/0x30
 ? btrfs_zone_finish_endio.part.0+0x34/0x160 [btrfs]
 ? btrfs_zone_finish_endio.part.0+0x19/0x160 [btrfs]
 btrfs_finish_one_ordered+0x7b8/0x1de0 [btrfs]
 ? rcu_is_watching+0x11/0xb0
 ? lock_release+0x47a/0x620
 ? btrfs_finish_ordered_zoned+0x59b/0x800 [btrfs]
 ? __pfx_btrfs_finish_one_ordered+0x10/0x10 [btrfs]
 ? btrfs_finish_ordered_zoned+0x358/0x800 [btrfs]
 ? __smp_call_single_queue+0x124/0x350
 ? rcu_is_watching+0x11/0xb0
 btrfs_work_helper+0x19f/0xc60 [btrfs]
 ? __pfx_try_to_wake_up+0x10/0x10
 ? _raw_spin_unlock_irq+0x24/0x50
 ? rcu_is_watching+0x11/0xb0
 process_one_work+0x8c1/0x1430
 ? __pfx_lock_acquire+0x10/0x10
 ? __pfx_process_one_work+0x10/0x10
 ? __pfx_do_raw_spin_lock+0x10/0x10
 ? _raw_spin_lock_irq+0x52/0x60
 worker_thread+0x100/0x12c0
 ? __kthread_parkme+0xc1/0x1f0
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x2ea/0x3c0
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x30/0x70
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1b/0x30
 </TASK>

On the zoned mode, writing to pre-allocated region means data relocation write. Such write always uses WRITE command so there is no need of splitting and rewriting logical address. Thus, we can just skip the function for the case.