Re: Re: [RESEND for nvme-6.1] nvmet-tcp: Fix NULL pointer dereference during release

[zhenwei pi]

On 9/20/22 23:34, Sagi Grimberg wrote:
> On 9/20/22 16:16, zhenwei pi wrote:
> > nvmet-tcp frees CMD buffers in nvmet_tcp_uninit_data_in_cmds(),
> > and waits the inflight IO requests in nvmet_sq_destroy(). During wait
> > the inflight IO requests, the callback nvmet_tcp_queue_response()
> > is called from backend after IO complete, this leads a typical
> > Use-After-Free issue like this:
> >
> >   BUG: kernel NULL pointer dereference, address: 0000000000000008
> >   #PF: supervisor read access in kernel mode
> >   #PF: error_code(0x0000) - not-present page
> >   PGD 107f80067 P4D 107f80067 PUD 10789e067 PMD 0
> >   Oops: 0000 [#1] PREEMPT SMP NOPTI
> >   CPU: 1 PID: 123 Comm: kworker/1:1H Kdump: loaded Tainted: 
> > G            E      6.0.0-rc2.bm.1-amd64 #15
> >   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 
> > rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> >   Workqueue: nvmet_tcp_wq nvmet_tcp_io_work [nvmet_tcp]
> >   RIP: 0010:shash_ahash_digest+0x2b/0x110
> >   Code: 1f 44 00 00 41 57 41 56 41 55 41 54 55 48 89 fd 53 48 89 f3 48 
> > 83 ec 08 44 8b 67 30 45 85 e4 74 1c 48 8b 57 38 b8 00 10 00 00 <44> 8b 
> > 7a 08 44 29 f8 39 42 0c 0f 46 42 0c 41 39 c4 76 43 48 8b 03
> >   RSP: 0018:ffffc9000051bdd8 EFLAGS: 00010206
> >   RAX: 0000000000001000 RBX: ffff888100ab5470 RCX: 0000000000000000
> >   RDX: 0000000000000000 RSI: ffff888100ab5470 RDI: ffff888100ab5420
> >   RBP: ffff888100ab5420 R08: ffff8881024d08c8 R09: ffff888103e1b4b8
> >   R10: 8080808080808080 R11: 0000000000000000 R12: 0000000000001000
> >   R13: 0000000000000000 R14: ffff88813412bd4c R15: ffff8881024d0800
> >   FS:  0000000000000000(0000) GS:ffff88883fa40000(0000) 
> > knlGS:0000000000000000
> >   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >   CR2: 0000000000000008 CR3: 0000000104b48000 CR4: 0000000000350ee0
> >   Call Trace:
> >    <TASK>
> >    nvmet_tcp_io_work+0xa52/0xb52 [nvmet_tcp]
> >    ? __switch_to+0x106/0x420
> >    process_one_work+0x1ae/0x380
> >    ? process_one_work+0x380/0x380
> >    worker_thread+0x30/0x360
> >    ? process_one_work+0x380/0x380
> >    kthread+0xe6/0x110
> >    ? kthread_complete_and_exit+0x20/0x20
> >    ret_from_fork+0x1f/0x30
> >
> > Suggested by Sagi, separate nvmet_tcp_uninit_data_in_cmds() into two
> > steps:
> >    uninit data in cmds                  <- new step 1
> >    nvmet_sq_destroy();
> >    cancel_work_sync(&queue->io_work);
> >    free CMD buffers                     <- new step 2
> >
> > Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
> > ---
> >   drivers/nvme/target/tcp.c | 19 ++++++++++++++++---
> >   1 file changed, 16 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
> > index c07de4f4f719..70baeab6af30 100644
> > --- a/drivers/nvme/target/tcp.c
> > +++ b/drivers/nvme/target/tcp.c
> > @@ -1406,14 +1406,26 @@ static void 
> > nvmet_tcp_uninit_data_in_cmds(struct nvmet_tcp_queue *queue)
> >       for (i = 0; i < queue->nr_cmds; i++, cmd++) {
> >           if (nvmet_tcp_need_data_in(cmd))
> >               nvmet_req_uninit(&cmd->req);
> > -
> > -        nvmet_tcp_free_cmd_buffers(cmd);
> >       }
> >       if (!queue->nr_cmds && nvmet_tcp_need_data_in(&queue->connect)) {
> >           /* failed in connect */
> > -        nvmet_tcp_finish_cmd(&queue->connect);
>
> I think that nvmet_tcp_finish_cmd is now redundant and can be removed
> if we fold it to its single remaining call-site.

Hi, Sagi

What about letting this patch fix the kernel panic only, and I'll send a 
followup patch to remove nvmet_tcp_finish_cmd after this patch applies?

> Other than that,
> Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>

--
zhenwei pi