On Tue 21-12-21 11:21:34, Yu Kuai wrote: > 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] raw: 0000000000000000 00000000001c001c 00000001ffffffff 0000000000000000 > [ 2073.020411] page dumped because: kasan: bad access detected > [ 2073.020412] > [ 2073.020414] Memory state around the buggy address: > [ 2073.020420] ffff8000ccf64000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 2073.020424] ffff8000ccf64080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 2073.020428] >ffff8000ccf64100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 2073.020430] ^ > [ 2073.020434] ffff8000ccf64180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 2073.020438] ffff8000ccf64200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 2073.020439] ================================================================== > > The same problem exist in mainline as well. > > This is because oom_bfqq is moved to a non-root group, thus root_group > is freed earlier. > > Thus fix the problem by don't move oom_bfqq. > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> Makes sense. Feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > --- > block/bfq-cgroup.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c > index 0f62546a72d4..8e8cf6b3d946 100644 > --- a/block/bfq-cgroup.c > +++ b/block/bfq-cgroup.c > @@ -651,6 +651,12 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, > if (old_parent == bfqg) > return; > > + /* > + * oom_bfqq is not allowed to move, oom_bfqq will hold ref to root_group > + * until elevator exit. > + */ > + if (bfqq == &bfqd->oom_bfqq) > + return; > /* > * Get extra reference to prevent bfqq from being freed in > * next possible expire or deactivate. > -- > 2.31.1 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
