On 12/21/19 7:30 AM, Hillf Danton wrote: > > On Fri, 20 Dec 2019 23:58:08 -0800 >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: 7ddd09fc Add linux-next specific files for 20191220 >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=12e1823ee00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=f183b01c3088afc6 >> dashboard link: https://syzkaller.appspot.com/bug?extid=8e7705a7ae1bdce77c07 >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >> >> Unfortunately, I don't have any reproducer for this crash yet. >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+8e7705a7ae1bdce77c07@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> ================================================================== >> BUG: KASAN: use-after-free in io_wq_flush+0x1f7/0x210 fs/io-wq.c:1009 >> Read of size 8 at addr ffff8880a8453d00 by task kworker/0:1/12 >> >> CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted >> 5.5.0-rc2-next-20191220-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >> Google 01/01/2011 >> Workqueue: events io_ring_file_ref_switch >> Call Trace: >> __dump_stack lib/dump_stack.c:77 [inline] >> dump_stack+0x197/0x210 lib/dump_stack.c:118 >> print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 >> __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 >> kasan_report+0x12/0x20 mm/kasan/common.c:639 >> __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135 >> io_wq_flush+0x1f7/0x210 fs/io-wq.c:1009 >> io_destruct_skb+0x8e/0xc0 fs/io_uring.c:4668 >> skb_release_head_state+0xeb/0x260 net/core/skbuff.c:652 >> skb_release_all+0x16/0x60 net/core/skbuff.c:663 >> __kfree_skb net/core/skbuff.c:679 [inline] >> kfree_skb net/core/skbuff.c:697 [inline] >> kfree_skb+0x101/0x420 net/core/skbuff.c:691 >> io_ring_file_put fs/io_uring.c:4836 [inline] >> io_ring_file_ref_switch+0x68a/0xac0 fs/io_uring.c:4881 >> process_one_work+0x9af/0x1740 kernel/workqueue.c:2264 >> worker_thread+0x98/0xe40 kernel/workqueue.c:2410 >> kthread+0x361/0x430 kernel/kthread.c:255 >> ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 >> >> Allocated by task 9937: >> save_stack+0x23/0x90 mm/kasan/common.c:72 >> set_track mm/kasan/common.c:80 [inline] >> __kasan_kmalloc mm/kasan/common.c:513 [inline] >> __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486 >> kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527 >> kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551 >> kmalloc include/linux/slab.h:555 [inline] >> kzalloc include/linux/slab.h:669 [inline] >> io_wq_create+0x52/0xa40 fs/io-wq.c:1024 >> io_sq_offload_start fs/io_uring.c:5244 [inline] >> io_uring_create fs/io_uring.c:6002 [inline] >> io_uring_setup+0xf4a/0x2080 fs/io_uring.c:6062 >> __do_sys_io_uring_setup fs/io_uring.c:6075 [inline] >> __se_sys_io_uring_setup fs/io_uring.c:6072 [inline] >> __x64_sys_io_uring_setup+0x54/0x80 fs/io_uring.c:6072 >> do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> >> Freed by task 9935: >> save_stack+0x23/0x90 mm/kasan/common.c:72 >> set_track mm/kasan/common.c:80 [inline] >> kasan_set_free_info mm/kasan/common.c:335 [inline] >> __kasan_slab_free+0x102/0x150 mm/kasan/common.c:474 >> kasan_slab_free+0xe/0x10 mm/kasan/common.c:483 >> __cache_free mm/slab.c:3426 [inline] >> kfree+0x10a/0x2c0 mm/slab.c:3757 >> io_wq_destroy+0x2ce/0x3c0 fs/io-wq.c:1116 >> io_finish_async+0x128/0x1b0 fs/io_uring.c:4657 >> io_ring_ctx_free fs/io_uring.c:5569 [inline] >> io_ring_ctx_wait_and_kill+0x330/0x9a0 fs/io_uring.c:5644 >> io_uring_release+0x42/0x50 fs/io_uring.c:5652 >> __fput+0x2ff/0x890 fs/file_table.c:280 >> ____fput+0x16/0x20 fs/file_table.c:313 >> task_work_run+0x145/0x1c0 kernel/task_work.c:113 >> tracehook_notify_resume include/linux/tracehook.h:188 [inline] >> exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164 >> prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] >> syscall_return_slowpath arch/x86/entry/common.c:278 [inline] >> do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> >> The buggy address belongs to the object at ffff8880a8453d00 >> which belongs to the cache kmalloc-192 of size 192 >> The buggy address is located 0 bytes inside of >> 192-byte region [ffff8880a8453d00, ffff8880a8453dc0) >> The buggy address belongs to the page: >> page:ffffea0002a114c0 refcount:1 mapcount:0 mapping:ffff8880aa400000 >> index:0x0 >> raw: 00fffe0000000200 ffffea0002644808 ffffea0002482f08 ffff8880aa400000 >> raw: 0000000000000000 ffff8880a8453000 0000000100000010 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff8880a8453c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> ffff8880a8453c80: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc >>> ffff8880a8453d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ^ >> ffff8880a8453d80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >> ffff8880a8453e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== > > Erase ctx's io_wq before destroying. > > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -4651,12 +4651,13 @@ static void io_sq_thread_stop(struct io_ > > static void io_finish_async(struct io_ring_ctx *ctx) > { > + struct io_wq *io_wq; > + > io_sq_thread_stop(ctx); > > - if (ctx->io_wq) { > - io_wq_destroy(ctx->io_wq); > - ctx->io_wq = NULL; > - } > + io_wq = xchg(&ctx->io_wq, NULL); > + if (io_wq) > + io_wq_destroy(io_wq); > } > > #if defined(CONFIG_UNIX) I actually think we can just kill the flush off the skb put path, it's not needed. -- Jens Axboe
