On Mon, Jun 23, 2025 at 01:33:44PM -0700, Caleb Sander Mateos wrote: > On Mon, Jun 23, 2025 at 2:13 AM Changhui Zhong <czhong@xxxxxxxxxx> wrote: > > > > On Mon, Jun 23, 2025 at 12:02 PM Ming Lei <ming.lei@xxxxxxxxxx> wrote: > > > > > > Hi Changhui, > > > > > > On Mon, Jun 23, 2025 at 10:58:24AM +0800, Changhui Zhong wrote: > > > > Hello, > > > > > > > > the following kernel panic was triggered by ubdsrv generic/002, > > > > please help check and let me know if you need any info/test, thanks. > > > > > > > > commit HEAD: > > > > > > > > commit 2589cd05008205ee29f5f66f24a684732ee2e3a3 > > > > Merge: 98d0347fe8fb e1c75831f682 > > > > Author: Jens Axboe <axboe@xxxxxxxxx> > > > > Date: Wed Jun 18 05:11:50 2025 -0600 > > > > > > > > Merge branch 'io_uring-6.16' into for-next > > > > > > > > * io_uring-6.16: > > > > io_uring: fix potential page leak in io_sqe_buffer_register() > > > > io_uring/sqpoll: don't put task_struct on tctx setup failure > > > > io_uring: remove duplicate io_uring_alloc_task_context() definition > > > > > > The above branch has been merged to v6.16-rc3, can you reproduce it with -rc3? > > > > > > I tried to duplicate in my test VM, not succeed with -rc3. > > > > > > ... > > > > > > > [ 7044.064528] BUG: kernel NULL pointer dereference, address: 0000000000000001 > > > > [ 7044.071507] #PF: supervisor read access in kernel mode > > > > [ 7044.076653] #PF: error_code(0x0000) - not-present page > > > > [ 7044.081801] PGD 462c42067 P4D 462c42067 PUD 462c43067 PMD 0 > > > > [ 7044.087488] Oops: Oops: 0000 [#1] SMP NOPTI > > > > [ 7044.091685] CPU: 13 UID: 0 PID: 367 Comm: kworker/13:1H Not tainted > > > > 6.16.0-rc2+ #1 PREEMPT(voluntary) > > > > [ 7044.100991] Hardware name: Dell Inc. PowerEdge R640/0X45NX, BIOS > > > > 2.22.2 09/12/2024 > > > > [ 7044.108565] Workqueue: kblockd blk_mq_requeue_work > > > > [ 7044.113374] RIP: 0010:__io_req_task_work_add+0x18/0x1f0 > > > > > > Can you share where the above line points to source line if it can be > > > reproduced in -rc3? > > > > > > gdb> l *(__io_req_task_work_add+0x18) > > > > > > > > > Thanks, > > > Ming > > > > > > > now successfully reproduced on v6.16-rc3, more loop tests are needed > > to trigger this issue， > > > > [ 8898.102836] BUG: kernel NULL pointer dereference, address: 0000000000000001 > > [ 8898.109848] #PF: supervisor read access in kernel mode > > [ 8898.115011] #PF: error_code(0x0000) - not-present page > > [ 8898.120161] PGD 80000001bcd7b067 P4D 80000001bcd7b067 PUD 1ee49f067 PMD 0 > > [ 8898.127043] Oops: Oops: 0000 [#1] SMP PTI > > [ 8898.131065] CPU: 2 UID: 0 PID: 47056 Comm: kworker/2:2H Not tainted > > 6.16.0-rc3 #1 PREEMPT(voluntary) > > [ 8898.140283] Hardware name: Dell Inc. PowerEdge R340/045M96, BIOS > > 2.17.3 09/12/2024 > > [ 8898.147860] Workqueue: kblockd blk_mq_requeue_work > > [ 8898.152658] RIP: 0010:__io_req_task_work_add+0x18/0x1f0 > > [ 8898.157895] Code: 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 > > 90 90 66 0f 1f 00 0f 1f 44 00 00 41 56 41 55 41 54 55 53 48 8b 6f 60 > > 48 89 fb <f6> 45 01 20 0f 84 8e 00 00 00 31 c0 f6 47 48 0c 0f 94 c0 21 > > c6 41 > > Disassembling this: > 0: 41 56 push r14 > 2: 41 55 push r13 > 4: 41 54 push r12 > 6: 55 push rbp > 7: 53 push rbx > 8: 48 8b 6f 60 mov rbp,QWORD PTR [rdi+0x60] > c: 48 89 fb mov rbx,rdi > f: f6 45 01 20 test BYTE PTR [rbp+0x1],0x20 <--here > 13: 0f 84 8e 00 00 00 je 0xa7 > 19: 31 c0 xor eax,eax > 1b: f6 47 48 0c test BYTE PTR [rdi+0x48],0xc > 1f: 0f 94 c0 sete al > 22: 21 c6 and esi,eax > > So we look to be at the start of __io_req_task_work_add(). rdi stores > req, rbp stores req->ctx, and so the test instruction that's faulting > is loading (the second byte of) req->ctx->flags for the > req->ctx->flags & IORING_SETUP_DEFER_TASKRUN check. This means > req->ctx is NULL. Is it possible the req has already been completed or > cancelled? The stacktrace shows that this is coming from > blk_mq_requeue_work, which is definitely interesting. > The issue should be in handling UBLK_IO_NEED_GET_DATA, -EIOCBQUEUED is returned without setting io->cmd. I will send a fix soon. Thanks Ming
