Overview
About vulnerability
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().
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , TuxCare 9.6 ESU
- Affected packages:
- kernel @ 4.18.0 (+4 more)
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().