Vulnerability CVE-2021-47066
Published: 2024-02-29   Modified: 2024-03-01

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

async_xor: increase src_offs when dropping destination page

Now we support sharing one page if PAGE_SIZE is not equal stripe size. To
support this, it needs to support calculating xor value with different
offsets for each r5dev. One offset array is used to record those offsets.

In RMW mode, parity page is used as a source page. It sets
ASYNC_TX_XOR_DROP_DST before calculating xor value in ops_run_prexor5.
So it needs to add src_list and src_offs at the same time. Now it only
needs src_list. So the xor value which is calculated is wrong. It can
cause data corruption problem.

I can reproduce this problem 100% on a POWER8 machine. The steps are:

mdadm -CR /dev/md0 -l5 -n3 /dev/sdb1 /dev/sdc1 /dev/sdd1 --size=3G
mkfs.xfs /dev/md0
mount /dev/md0 /mnt/test
mount: /mnt/test: mount(2) system call failed: Structure needs cleaning.

 References:
https://git.kernel.org/stable/c/cab2e8e5997b592fdb7d02cf2387b4b8e3057174
https://git.kernel.org/stable/c/29ffa50f33de824b5491f8239c88c4a0efdd03af
https://git.kernel.org/stable/c/53f8208e11abd6dde9480dfcb97fecdb1bc2ac18
https://git.kernel.org/stable/c/ceaf2966ab082bbc4d26516f97b3ca8a676e2af8
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