From: Yu Kuai yukuai3@huawei.com
hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I66VJO CVE: NA
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Our test report a uaf for 'bfqq->bic' in 5.10:
================================================================== BUG: KASAN: use-after-free in bfq_select_queue+0x378/0xa30 Read of size 8 at addr ffff88810efb42d8 by task fsstress/2318352
CPU: 6 PID: 2318352 Comm: fsstress Kdump: loaded Not tainted 5.10.0-60.18.0.50.h602.kasan.eulerosv2r11.x86_64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-20220320_160524-szxrtosci10000 04/01/2014 Call Trace: dump_stack+0x9c/0xd3 print_address_description.constprop.0+0x19/0x170 ? bfq_select_queue+0x378/0xa30 __kasan_report.cold+0x6c/0x84 ? bfq_select_queue+0x378/0xa30 kasan_report+0x3a/0x50 bfq_select_queue+0x378/0xa30 ? bfq_bfqq_expire+0x6c0/0x6c0 ? bfq_mark_bfqq_busy+0x1f/0x30 ? _raw_spin_lock_irq+0x7b/0xd0 __bfq_dispatch_request+0x1c4/0x220 bfq_dispatch_request+0xe8/0x130 __blk_mq_do_dispatch_sched+0x3f4/0x560 ? blk_mq_sched_mark_restart_hctx+0x50/0x50 ? bfq_init_rq+0x128/0x940 ? pvclock_clocksource_read+0xf6/0x1d0 blk_mq_do_dispatch_sched+0x62/0xb0 __blk_mq_sched_dispatch_requests+0x215/0x2a0 ? blk_mq_do_dispatch_ctx+0x3a0/0x3a0 ? bfq_insert_request+0x193/0x3f0 blk_mq_sched_dispatch_requests+0x8f/0xd0 __blk_mq_run_hw_queue+0x98/0x180 __blk_mq_delay_run_hw_queue+0x22b/0x240 ? bfq_asymmetric_scenario+0x160/0x160 blk_mq_run_hw_queue+0xe3/0x190 ? bfq_insert_request+0x3f0/0x3f0 blk_mq_sched_insert_requests+0x107/0x200 blk_mq_flush_plug_list+0x26e/0x3c0 ? blk_mq_insert_requests+0x250/0x250 ? blk_check_plugged+0x190/0x190 blk_finish_plug+0x63/0x90 __iomap_dio_rw+0x7b5/0x910 ? iomap_dio_actor+0x150/0x150 ? userns_put+0x70/0x70 ? userns_put+0x70/0x70 ? avc_has_perm_noaudit+0x1d0/0x1d0 ? down_read+0xd5/0x1a0 ? down_read_killable+0x1b0/0x1b0 ? from_kgid+0xa0/0xa0 iomap_dio_rw+0x36/0x80 ext4_dio_read_iter+0x146/0x190 [ext4] ext4_file_read_iter+0x1e2/0x230 [ext4] new_sync_read+0x29f/0x400 ? default_llseek+0x160/0x160 ? find_isec_ns+0x8d/0x2e0 ? avc_policy_seqno+0x27/0x40 ? selinux_file_permission+0x34/0x180 ? security_file_permission+0x135/0x2b0 vfs_read+0x24e/0x2d0 ksys_read+0xd5/0x1b0 ? __ia32_sys_pread64+0x160/0x160 ? __audit_syscall_entry+0x1cc/0x220 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x61/0xc6 RIP: 0033:0x7ff05f96fe62 Code: c0 e9 b2 fe ff ff 50 48 8d 3d 12 04 0c 00 e8 b5 fe 01 00 0f 1f 44 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 48 83 ec 28 48 89 54 24 RSP: 002b:00007fffd30c0ff8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00000000000000a5 RCX: 00007ff05f96fe62 RDX: 000000000001d000 RSI: 0000000001ffc000 RDI: 0000000000000003 RBP: 0000000000000003 R08: 0000000002019000 R09: 0000000000000000 R10: 00007ff05fa65290 R11: 0000000000000246 R12: 0000000000131800 R13: 000000000001d000 R14: 0000000000000000 R15: 0000000001ffc000
Allocated by task 2318348: kasan_save_stack+0x1b/0x40 __kasan_kmalloc.constprop.0+0xb5/0xe0 kmem_cache_alloc_node+0x15d/0x480 ioc_create_icq+0x68/0x2e0 blk_mq_sched_assign_ioc+0xbc/0xd0 blk_mq_rq_ctx_init+0x4b0/0x600 __blk_mq_alloc_request+0x21f/0x2e0 blk_mq_submit_bio+0x27a/0xd60 __submit_bio_noacct_mq+0x10b/0x270 submit_bio_noacct+0x13d/0x150 submit_bio+0xbf/0x280 iomap_dio_submit_bio+0x155/0x180 iomap_dio_bio_actor+0x2f0/0x770 iomap_dio_actor+0xd9/0x150 iomap_apply+0x1d2/0x4f0 __iomap_dio_rw+0x43a/0x910 iomap_dio_rw+0x36/0x80 ext4_dio_write_iter+0x46f/0x730 [ext4] ext4_file_write_iter+0xd8/0x100 [ext4] new_sync_write+0x2ac/0x3a0 vfs_write+0x365/0x430 ksys_write+0xd5/0x1b0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x61/0xc6
Freed by task 2320929: kasan_save_stack+0x1b/0x40 kasan_set_track+0x1c/0x30 kasan_set_free_info+0x20/0x40 __kasan_slab_free+0x151/0x180 kmem_cache_free+0x9e/0x540 rcu_do_batch+0x292/0x700 rcu_core+0x270/0x2d0 __do_softirq+0xfd/0x402
Last call_rcu(): kasan_save_stack+0x1b/0x40 kasan_record_aux_stack+0xa8/0xf0 __call_rcu+0xa4/0x3a0 ioc_release_fn+0x45/0x120 process_one_work+0x3c5/0x730 worker_thread+0x93/0x650 kthread+0x1ba/0x210 ret_from_fork+0x22/0x30
Second to last call_rcu(): kasan_save_stack+0x1b/0x40 kasan_record_aux_stack+0xa8/0xf0 __call_rcu+0xa4/0x3a0 ioc_release_fn+0x45/0x120 process_one_work+0x3c5/0x730 worker_thread+0x93/0x650 kthread+0x1ba/0x210 ret_from_fork+0x22/0x30
The buggy address belongs to the object at ffff88810efb42a0 which belongs to the cache bfq_io_cq of size 160 The buggy address is located 56 bytes inside of 160-byte region [ffff88810efb42a0, ffff88810efb4340) The buggy address belongs to the page: page:00000000a519c14c refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88810efb4000 pfn:0x10efb4 head:00000000a519c14c order:1 compound_mapcount:0 flags: 0x17ffffc0010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff) raw: 0017ffffc0010200 0000000000000000 dead000000000122 ffff8881407c8600 raw: ffff88810efb4000 000000008024001a 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff88810efb4180: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff88810efb4200: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff88810efb4280: fc fc fc fc fa fb fb fb fb fb fb fb fb fb fb fb
^ ffff88810efb4300: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff88810efb4380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
Commit 3bc5e683c67d ("bfq: Split shared queues on move between cgroups") changes that move process to a new cgroup will allocate a new bfqq to use, however, the old bfqq and new bfqq can point to the same bic:
1) Initial state, two process with io in the same cgroup.
Process 1 Process 2 (BIC1) (BIC2) | Λ | Λ | | | | V | V | bfqq1 bfqq2
2) bfqq1 is merged to bfqq2.
Process 1 Process 2（cg1) (BIC1) (BIC2) | | -------------| V bfqq1 bfqq2(coop)
3) Process 1 exit, then issue new io(denoce IOA) from Process 2.
(BIC2) | Λ | | V | bfqq2(coop)
4) Before IOA is completed, move Process 2 to another cgroup and issue io.
Process 2 (BIC2) Λ |--------------\ | V bfqq2 bfqq3
Now that BIC2 points to bfqq3, while bfqq2 and bfqq3 both point to BIC2. If all the requests are completed, and Process 2 exit, BIC2 will be freed while there is no guarantee that bfqq2 will be freed before BIC2.
Fix the problem by clearing bfqq->bic if process references is decreased to zero, since that they are not related anymore.
Fixes: 3bc5e683c67d ("bfq: Split shared queues on move between cgroups") Signed-off-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Hou Tao houtao1@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- block/bfq-iosched.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 6edc00da5b57..829e713639ad 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2775,6 +2775,15 @@ void bfq_release_process_ref(struct bfq_data *bfqd, struct bfq_queue *bfqq) bfqq != bfqd->in_service_queue) bfq_del_bfqq_busy(bfqd, bfqq, false);
+ /* + * __bfq_bic_change_cgroup() just reset bic->bfqq so that a new bfqq + * will be created to handle new io, while old bfqq will stay around + * until all the requests are completed. It's unsafe to keep bfqq->bic + * since they are not related anymore. + */ + if (bfqq_process_refs(bfqq) == 1) + bfqq->bic = NULL; + bfq_put_queue(bfqq); }