linux-kernel - Re: [syzbot] [usb?] INFO: rcu detected stall in raw

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Date: Wed, 12 Jun 2024 21:23:17 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: syzbot <syzbot+5f996b83575ef4058638@...kaller.appspotmail.com>
Cc: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
  linux-usb@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [usb?] INFO: rcu detected stall in raw_ioctl

Try again, with the "#syz test:" command present this time.  Sigh.

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@...kaller.appspotmail.com
> 
> 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

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git 8867bbd4a056

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;
 	}