CVE-2023-54132

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

erofs: stop parsing non-compact HEAD index if clusterofs is invalid

Syzbot generated a crafted image [1] with a non-compact HEAD index of clusterofs 33024 while valid numbers should be 0 ~ lclustersize-1, which causes the following unexpected behavior as below:

BUG: unable to handle page fault for address: fffff52101a3fff9 #PF: supervisor read access in kernel mode #PF: errorcode(0x0000) - not-present page PGD 23ffed067 P4D 23ffed067 PUD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 4398 Comm: kworker/u5:1 Not tainted 6.3.0-rc6-syzkaller-g09a9639e56c0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023 Workqueue: erofsworker zerofsdecompressqueuework RIP: 0010:zerofsdecompressqueue+0xb7e/0x2b40 ... Call Trace: <TASK> zerofsdecompressqueuework+0x99/0xe0 processonework+0x8f6/0x1170 workerthread+0xa63/0x1210 kthread+0x270/0x300 retfromfork+0x1f/0x30

Note that normal images or images using compact indexes are not impacted. Let's fix this now.

[1] https://lore.kernel.org/r/000000000000ec75b005ee97fbaa@google.com