Re: 答复: [PATCH v3] usb: gadget: u_serial: Disable ep before setting port to null to fix the crash caused by port being null

["gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>]

On Fri, Jan 17, 2025 at 05:04:30AM +0000, 胡连勤 wrote:
> Hi  Jon：
> 
> > >>> Considering that in some extreme cases, when performing the
> > >>> unbinding operation, gserial_disconnect has cleared gser->ioport,
> > >>> which triggers gadget reconfiguration, and then calls
> > >>> gs_read_complete, resulting in access to a null pointer. Therefore,
> > >>> ep is disabled before gserial_disconnect sets port to null to prevent this
> > from happening.
> > >>>
> > >>> Call trace:
> > >>>    gs_read_complete+0x58/0x240
> > >>>    usb_gadget_giveback_request+0x40/0x160
> > >>>    dwc3_remove_requests+0x170/0x484
> > >>>    dwc3_ep0_out_start+0xb0/0x1d4
> > >>>    __dwc3_gadget_start+0x25c/0x720
> > >>>    kretprobe_trampoline.cfi_jt+0x0/0x8
> > >>>    kretprobe_trampoline.cfi_jt+0x0/0x8
> > >>>    udc_bind_to_driver+0x1d8/0x300
> > >>>    usb_gadget_probe_driver+0xa8/0x1dc
> > >>>    gadget_dev_desc_UDC_store+0x13c/0x188
> > >>>    configfs_write_iter+0x160/0x1f4
> > >>>    vfs_write+0x2d0/0x40c
> > >>>    ksys_write+0x7c/0xf0
> > >>>    __arm64_sys_write+0x20/0x30
> > >>>    invoke_syscall+0x60/0x150
> > >>>    el0_svc_common+0x8c/0xf8
> > >>>    do_el0_svc+0x28/0xa0
> > >>>    el0_svc+0x24/0x84
> > >>>
> > >>> Fixes: c1dca562be8a ("usb gadget: split out serial core")
> > >>> Cc: stable@vger.kernel.org
> > >>> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > >>> Signed-off-by: Lianqin Hu <hulianqin@vivo.com>
> > >>> ---
> > >>>
> > >>> Changes in v3:
> > >>>    - Add --- line above the version tag information
> > >>>    - Remove extra blank lines in commit messages
> > >>>    - Version tag information from v2 to changes in v2
> > >>>    - Link to v2:
> > >>>
> > https://lo/
> > >>>
> > re.kernel.org%2Fall%2FTYUPR06MB6217DAA095A9863D4B58D57CD23B2%40T
> > YUPR
> > >>>
> > 06MB6217.apcprd06.prod.outlook.com%2F&data=05%7C02%7Chulianqin%40
> > viv
> > >>>
> > o.com%7Cc88bd260faf9470d244f08dd363eb8df%7C923e42dc48d54cbeb5821
> > a797
> > >>>
> > a6412ed%7C0%7C0%7C638726365197191059%7CUnknown%7CTWFpbGZsb3d
> > 8eyJFbXB
> > >>>
> > 0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFp
> > bCI
> > >>>
> > sIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=G4l0lGF093J44BuTeGpEYpYvC
> > MGiK3d
> > >>> TnR%2Fd2Zn8Q1U%3D&reserved=0
> > >>>
> > >>> Changes in v2:
> > >>>    - Remove some address information from patch descriptions
> > >>>    - Link to v1:
> > https://lore.k/
> > ernel.org%2Fall%2FTYUPR06MB621763AB815989161F4033AFD2762%40TYUPR
> > 06MB6217.apcprd06.prod.outlook.com%2F&data=05%7C02%7Chulianqin%40
> > vivo.com%7Cc88bd260faf9470d244f08dd363eb8df%7C923e42dc48d54cbeb58
> > 21a797a6412ed%7C0%7C0%7C638726365197206594%7CUnknown%7CTWFpb
> > GZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4z
> > MiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=6rGddQJ
> > L9K%2Bqyr98IXYkf6zM8AzxN6%2FaJZztGybx%2FUw%3D&reserved=0
> > >>>    - Link to suggestions:
> > >>>
> > https://lo/
> > >>>
> > re.kernel.org%2Fall%2FTYUPR06MB6217DE28012FFEC5E808DD64D2962%40TY
> > UPR
> > >>>
> > 06MB6217.apcprd06.prod.outlook.com%2F&data=05%7C02%7Chulianqin%40
> > viv
> > >>>
> > o.com%7Cc88bd260faf9470d244f08dd363eb8df%7C923e42dc48d54cbeb5821
> > a797
> > >>>
> > a6412ed%7C0%7C0%7C638726365197216620%7CUnknown%7CTWFpbGZsb3d
> > 8eyJFbXB
> > >>>
> > 0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFp
> > bCI
> > >>>
> > sIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=7EvOpENpZd8s6S8PR1D%2B2
> > HnQmBLPa
> > >>> UNotpV5UGSDiDE%3D&reserved=0
> > >>>
> > >>>    drivers/usb/gadget/function/u_serial.c | 8 ++++----
> > >>>    1 file changed, 4 insertions(+), 4 deletions(-)
> > >>>
> > >>> diff --git a/drivers/usb/gadget/function/u_serial.c
> > >>> b/drivers/usb/gadget/function/u_serial.c
> > >>> index 53d9fc41acc5..bc143a86c2dd 100644
> > >>> --- a/drivers/usb/gadget/function/u_serial.c
> > >>> +++ b/drivers/usb/gadget/function/u_serial.c
> > >>> @@ -1420,6 +1420,10 @@ void gserial_disconnect(struct gserial *gser)
> > >>>     /* REVISIT as above: how best to track this? */
> > >>>     port->port_line_coding = gser->port_line_coding;
> > >>> +   /* disable endpoints, aborting down any active I/O */
> > >>> +   usb_ep_disable(gser->out);
> > >>> +   usb_ep_disable(gser->in);
> > >>> +
> > >>>     port->port_usb = NULL;
> > >>>     gser->ioport = NULL;
> > >>>     if (port->port.count > 0) {
> > >>> @@ -1431,10 +1435,6 @@ void gserial_disconnect(struct gserial *gser)
> > >>>     spin_unlock(&port->port_lock);
> > >>>     spin_unlock_irqrestore(&serial_port_lock, flags);
> > >>> -   /* disable endpoints, aborting down any active I/O */
> > >>> -   usb_ep_disable(gser->out);
> > >>> -   usb_ep_disable(gser->in);
> > >>> -
> > >>>     /* finally, free any unused/unusable I/O buffers */
> > >>>     spin_lock_irqsave(&port->port_lock, flags);
> > >>>     if (port->port.count == 0)
> > >>
> > >>
> > >> We have observed a reboot regression on Tegra234 (I have not tried
> > >> other
> > >> boards) and bisect is pointing to this commit. Reverting this on top
> > >> of mainline is fixing the problem.
> > >>
> > >> With this change, when the board reboots we see ...
> > >>
> > >> [   59.918177] tegra-xudc 3550000.usb: ep 3 disabled
> > >> [   59.923097] tegra-xudc 3550000.usb: ep 2 disabled
> > >> [   59.927955] tegra-xudc 3550000.usb: ep 5 disabled
> > >> [   80.911432] rcu: INFO: rcu_preempt self-detected stall on CPU
> > >> [   80.917354] rcu:     6-....: (5248 ticks this GP)
> > idle=ec24/1/0x4000000000000000 softirq=1213/1213 fqs=2623
> > >> [   80.927146] rcu:     (t=5253 jiffies g=3781 q=1490 ncpus=12)
> > >> [   80.932704] Sending NMI from CPU 6 to CPUs 2:
> > >> [   90.981555] CPU: 6 UID: 0 PID: 18 Comm: rcu_exp_gp_kthr Not tainted
> > 6.13.0-rc7-00043-g619f0b6fad52 #1
> > >> [   90.981558] Hardware name: NVIDIA NVIDIA Jetson AGX Orin Developer
> > Kit/Jetson, BIOS 00.0.0-dev-main_92e5ae_88fd1_296de 12/16/2024
> > >> [   90.981559] pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS
> > BTYPE=--)
> > >> [   90.981562] pc : smp_call_function_single+0xdc/0x1a0
> > >> [   90.981574] lr : __sync_rcu_exp_select_node_cpus+0x228/0x3c0
> > >> [   90.981578] sp : ffff800082eb3cd0
> > >> [   90.981579] x29: ffff800082eb3cd0 x28: 0000000000000010 x27:
> > ffff0000802933c0
> > >> [   90.981582] x26: ffff0007a8a1d700 x25: ffff800082895500 x24:
> > ffff800080132018
> > >> [   90.981584] x23: 0000000000000014 x22: ffff800081fb7700 x21:
> > ffff80008280d970
> > >> [   90.981586] x20: 0000000000000feb x19: ffff800082eb3d00 x18:
> > 0000000000000000
> > >> [   90.981588] x17: 0000000000000000 x16: 0000000000000000 x15:
> > 0000000000000000
> > >> [   90.981590] x14: ffff000080293440 x13: 0000000000000001 x12:
> > 0000000000000000
> > >> [   90.981591] x11: ffff800081fb2388 x10: ffff0000802933c0 x9 :
> > 0000000000000001
> > >> [   90.981593] x8 : 0000000000000040 x7 : 0000000000017068 x6 :
> > ffff800080132018
> > >> [   90.981595] x5 : 0000000000000000 x4 : ffff0007a8a4f9c8 x3 :
> > 0000000000000001
> > >> [   90.981597] x2 : 0000000000000000 x1 : ffff0007a8a4f9c0 x0 :
> > 0000000000000004
> > >> [   90.981599] Call trace:
> > >> [   90.981601]  smp_call_function_single+0xdc/0x1a0 (P)
> > >> [   90.981605]  __sync_rcu_exp_select_node_cpus+0x228/0x3c0
> > >> [   90.981607]  sync_rcu_exp_select_cpus+0x13c/0x2a0
> > >> [   90.981609]  wait_rcu_exp_gp+0x18/0x30
> > >> [   90.981611]  kthread_worker_fn+0xd0/0x188
> > >> [   90.981614]  kthread+0x118/0x11c
> > >> [   90.981619]  ret_from_fork+0x10/0x20
> > >> [  101.416347] sched: DL replenish lagged too much
> > >>
> > >
> > > Odd, you have a usb-serial gadget device in this system that is
> > > disconnecting somehow?  That oops doesn't point to anything in the usb
> > > gadget codebase, "all" we have done is move the call to shutdown the
> > > endpoints to earlier in the disconnect function.
> >
> > Yes the board starts usb-serial and usb-ethernet gadget and on reboot when
> > tearing it down I am seeing the above. As soon as it disables the tegra-xudc
> > endpoints (as seen above) the board appears to stall.
> >
> > > I'm glad to revert this, but it feels really odd that this is causing
> > > you an rcu stall issue.
> >
> > Thanks. I can't say I understand it either, but I am certain it is caused by this
> > change.
> >
> > Happy to run any tests to narrow this down a bit.
> 
> I'm really sorry. If we are sure that the problem is caused by this patch, we will roll it back first. In addition,
> what are the differences between the serial use of Tegra234 board and mobile phones?
> When we consider other solutions, we need to take this usage scenario of Tegra234 board into consideration.

Revert sent here now:
	https://lore.kernel.org/r/2025011711-yippee-fever-a737@gregkh