Re: [syzbot] [usb?] INFO: rcu detected stall in raw_ioctl

From: Alan Stern
Date: Wed Jun 12 2024 - 10:38:06 EST


On Tue, Jun 11, 2024 at 11:03:03AM -0700, syzbot wrote:
> Hello,
>
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
>
> Reported-and-tested-by: syzbot+5f996b83575ef4058638@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> Tested on:
>
> commit: 8867bbd4 mm: arm64: Fix the out-of-bounds issue in con..
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
> console output: https://syzkaller.appspot.com/x/log.txt?x=14e092de980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=3b4350cf56c61c80
> dashboard link: https://syzkaller.appspot.com/bug?extid=5f996b83575ef4058638
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> patch: https://syzkaller.appspot.com/x/patch.diff?x=137c697e980000
>
> Note: testing is done by a robot and is best-effort only.

Let's try Greg's suggestion to replace dev_err() with
dev_err_ratelimited().

Alan Stern

Index: usb-devel/drivers/usb/class/cdc-wdm.c
===================================================================
--- usb-devel.orig/drivers/usb/class/cdc-wdm.c
+++ usb-devel/drivers/usb/class/cdc-wdm.c
@@ -266,14 +266,14 @@ static void wdm_int_callback(struct urb
dev_err(&desc->intf->dev, "Stall on int endpoint\n");
goto sw; /* halt is cleared in work */
default:
- dev_err(&desc->intf->dev,
+ dev_err_ratelimited(&desc->intf->dev,
"nonzero urb status received: %d\n", status);
break;
}
}

if (urb->actual_length < sizeof(struct usb_cdc_notification)) {
- dev_err(&desc->intf->dev, "wdm_int_callback - %d bytes\n",
+ dev_err_ratelimited(&desc->intf->dev, "wdm_int_callback - %d bytes\n",
urb->actual_length);
goto exit;
}