Messages in this thread | | | Date | Wed, 17 Nov 2021 17:00:07 -0500 | From | Qian Cai <> | Subject | BUG: KASAN: use-after-free in dec_rlimit_ucounts |
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Hi there, I can still reproduce this quickly on today's linux-next and all the way back to 5.15-rc6 by running a syscall fuzzer for a while. The trace points out to this line,
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
It looks KASAN indicated that that "ns" had already been freed. Is that possible or perhaps this is more of refcount issue?
BUG: KASAN: use-after-free in dec_rlimit_ucounts Read of size 8 at addr ffff0008c0739860 by task trinity-c27/10924
CPU: 27 PID: 10924 Comm: trinity-c27 Not tainted 5.15.0-next-20211115-dirty #192 Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 1.6 06/28/2020 Call trace: dump_backtrace show_stack dump_stack_lvl print_address_description.constprop.0 kasan_report __asan_report_load8_noabort dec_rlimit_ucounts dec_rlimit_ucounts at kernel/ucount.c:284 mqueue_evict_inode mqueue_evict_inode at ipc/mqueue.c:544 evict iput.part.0 iput __arm64_sys_mq_unlink invoke_syscall el0_svc_common.constprop.0 do_el0_svc el0_svc el0t_64_sync_handler el0t_64_sync
Allocated by task 10615: kasan_save_stack __kasan_slab_alloc slab_post_alloc_hook kmem_cache_alloc create_user_ns unshare_userns ksys_unshare __arm64_sys_unshare invoke_syscall el0_svc_common.constprop.0 do_el0_svc el0_svc el0t_64_sync_handler el0t_64_sync
Freed by task 8660: kasan_save_stack kasan_set_track kasan_set_free_info __kasan_slab_free slab_free_freelist_hook kmem_cache_free free_user_ns process_one_work worker_thread kthread ret_from_fork
Last potentially related work creation: kasan_save_stack __kasan_record_aux_stack kasan_record_aux_stack_noalloc insert_work __queue_work queue_work_on __put_user_ns put_cred_rcu rcu_do_batch rcu_core rcu_core_si __do_softirq
The buggy address belongs to the object at ffff0008c07395e8 which belongs to the cache user_namespace of size 768 The buggy address is located 632 bytes inside of 768-byte region [ffff0008c07395e8, ffff0008c07398e8) The buggy address belongs to the page: page:fffffc002301ce00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff0008c073cec8 pfn:0x940738 head:fffffc002301ce00 order:3 compound_mapcount:0 compound_pincount:0 memcg:ffff0008b9b5f101 flags: 0xbfffc0000010200(slab|head|node=0|zone=2|lastcpupid=0xffff) raw: 0bfffc0000010200 ffff000800f3e9c8 ffff000800f3e9c8 ffff000802e69b80 raw: ffff0008c073cec8 00000000001d0012 00000001ffffffff ffff0008b9b5f101 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff0008c0739700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff0008c0739780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff0008c0739800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff0008c0739880: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc ffff0008c0739900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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