CVE-2022-49179

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

block, bfq: don't move oom_bfqq

Our test report a UAF:

[ 2073.019181] ================================================================== [ 2073.019188] BUG: KASAN: use-after-free in __bfq_put_async_bfqq+0xa0/0x168 [ 2073.019191] Write of size 8 at addr ffff8000ccf64128 by task rmmod/72584 [ 2073.019192] [ 2073.019196] CPU: 0 PID: 72584 Comm: rmmod Kdump: loaded Not tainted 4.19.90-yk #5 [ 2073.019198] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 [ 2073.019200] Call trace: [ 2073.019203] dump_backtrace+0x0/0x310 [ 2073.019206] show_stack+0x28/0x38 [ 2073.019210] dump_stack+0xec/0x15c [ 2073.019216] print_address_description+0x68/0x2d0 [ 2073.019220] kasan_report+0x238/0x2f0 [ 2073.019224] __asan_store8+0x88/0xb0 [ 2073.019229] __bfq_put_async_bfqq+0xa0/0x168 [ 2073.019233] bfq_put_async_queues+0xbc/0x208 [ 2073.019236] bfq_pd_offline+0x178/0x238 [ 2073.019240] blkcg_deactivate_policy+0x1f0/0x420 [ 2073.019244] bfq_exit_queue+0x128/0x178 [ 2073.019249] blk_mq_exit_sched+0x12c/0x160 [ 2073.019252] elevator_exit+0xc8/0xd0 [ 2073.019256] blk_exit_queue+0x50/0x88 [ 2073.019259] blk_cleanup_queue+0x228/0x3d8 [ 2073.019267] null_del_dev+0xfc/0x1e0 [null_blk] [ 2073.019274] null_exit+0x90/0x114 [null_blk] [ 2073.019278] __arm64_sys_delete_module+0x358/0x5a0 [ 2073.019282] el0_svc_common+0xc8/0x320 [ 2073.019287] el0_svc_handler+0xf8/0x160 [ 2073.019290] el0_svc+0x10/0x218 [ 2073.019291] [ 2073.019294] Allocated by task 14163: [ 2073.019301] kasan_kmalloc+0xe0/0x190 [ 2073.019305] kmem_cache_alloc_node_trace+0x1cc/0x418 [ 2073.019308] bfq_pd_alloc+0x54/0x118 [ 2073.019313] blkcg_activate_policy+0x250/0x460 [ 2073.019317] bfq_create_group_hierarchy+0x38/0x110 [ 2073.019321] bfq_init_queue+0x6d0/0x948 [ 2073.019325] blk_mq_init_sched+0x1d8/0x390 [ 2073.019330] elevator_switch_mq+0x88/0x170 [ 2073.019334] elevator_switch+0x140/0x270 [ 2073.019338] elv_iosched_store+0x1a4/0x2a0 [ 2073.019342] queue_attr_store+0x90/0xe0 [ 2073.019348] sysfs_kf_write+0xa8/0xe8 [ 2073.019351] kernfs_fop_write+0x1f8/0x378 [ 2073.019359] __vfs_write+0xe0/0x360 [ 2073.019363] vfs_write+0xf0/0x270 [ 2073.019367] ksys_write+0xdc/0x1b8 [ 2073.019371] __arm64_sys_write+0x50/0x60 [ 2073.019375] el0_svc_common+0xc8/0x320 [ 2073.019380] el0_svc_handler+0xf8/0x160 [ 2073.019383] el0_svc+0x10/0x218 [ 2073.019385] [ 2073.019387] Freed by task 72584: [ 2073.019391] __kasan_slab_free+0x120/0x228 [ 2073.019394] kasan_slab_free+0x10/0x18 [ 2073.019397] kfree+0x94/0x368 [ 2073.019400] bfqg_put+0x64/0xb0 [ 2073.019404] bfqg_and_blkg_put+0x90/0xb0 [ 2073.019408] bfq_put_queue+0x220/0x228 [ 2073.019413] __bfq_put_async_bfqq+0x98/0x168 [ 2073.019416] bfq_put_async_queues+0xbc/0x208 [ 2073.019420] bfq_pd_offline+0x178/0x238 [ 2073.019424] blkcg_deactivate_policy+0x1f0/0x420 [ 2073.019429] bfq_exit_queue+0x128/0x178 [ 2073.019433] blk_mq_exit_sched+0x12c/0x160 [ 2073.019437] elevator_exit+0xc8/0xd0 [ 2073.019440] blk_exit_queue+0x50/0x88 [ 2073.019443] blk_cleanup_queue+0x228/0x3d8 [ 2073.019451] null_del_dev+0xfc/0x1e0 [null_blk] [ 2073.019459] null_exit+0x90/0x114 [null_blk] [ 2073.019462] __arm64_sys_delete_module+0x358/0x5a0 [ 2073.019467] el0_svc_common+0xc8/0x320 [ 2073.019471] el0_svc_handler+0xf8/0x160 [ 2073.019474] el0_svc+0x10/0x218 [ 2073.019475] [ 2073.019479] The buggy address belongs to the object at ffff8000ccf63f00 which belongs to the cache kmalloc-1024 of size 1024 [ 2073.019484] The buggy address is located 552 bytes inside of 1024-byte region [ffff8000ccf63f00, ffff8000ccf64300) [ 2073.019486] The buggy address belongs to the page: [ 2073.019492] page:ffff7e000333d800 count:1 mapcount:0 mapping:ffff8000c0003a00 index:0x0 compound_mapcount: 0 [ 2073.020123] flags: 0x7ffff0000008100(slab|head) [ 2073.020403] raw: 07ffff0000008100 ffff7e0003334c08 ffff7e00001f5a08 ffff8000c0003a00 [ 2073.020409] ra ---truncated---

This vulnerability is rated as Moderate impact for Red Hat Enterprise Linux because exploitation requires local access to cause a kernel denial of service, without enabling direct remote code execution. The BFQ I/O scheduler is not enabled by default in standard Red Hat deployments, which utilize alternative schedulers such as mq-deadline or none for block storage. Triggering this flaw requires an uncommon environment where BFQ is explicitly selected alongside block cgroup deactivation or teardown, limiting the overall blast radius.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.