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

md/raid5-cache: fix null-ptr-deref for r5l_flush_stripe_to_raid()

r5l_flush_stripe_to_raid() will check if the list 'flushing_ios' is
empty, and then submit 'flush_bio', however, r5l_log_flush_endio()
is clearing the list first and then clear the bio, which will cause
null-ptr-deref:

T1: submit flush io
raid5d
handle_active_stripes
r5l_flush_stripe_to_raid
// list is empty
// add 'io_end_ios' to the list
bio_init
submit_bio
// io1

T2: io1 is done
r5l_log_flush_endio
list_splice_tail_init
// clear the list
T3: submit new flush io
...
r5l_flush_stripe_to_raid
// list is empty
// add 'io_end_ios' to the list
bio_init
bio_uninit
// clear bio->bi_blkg
submit_bio
// null-ptr-deref

Fix this problem by clearing bio before clearing the list in
r5l_log_flush_endio().

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-53210
• https://git.kernel.org/stable/c/0d0bd28c500173bfca78aa840f8f36d261ef1765
• https://git.kernel.org/stable/c/711fb92606208a8626b785da4f9f23d648a5b6c8
• https://git.kernel.org/stable/c/7a8b6d93991bf4b72b3f959baea35397c6c8e521
• https://git.kernel.org/stable/c/e46b2e7be8059d156af8c011dd8d665229b65886