From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qt1-f169.google.com (mail-qt1-f169.google.com [209.85.160.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A3D9D2253EB for ; Sat, 14 Mar 2026 16:42:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773506537; cv=none; b=jukAdMgjjgMj67QzRMGVwaH4i+Dy6j58fs41XtZ/P2GB/EbnRPBM38hCWXH1M2ap5iLfV/szF8igi2umXQ9TVITJiuRodaQY/DfxPulzTPlIptdHsuvoaSXwRsKLzn8j4rkw91cNWYXKRtgIFq/v44GoLvyfTqYD1Pky3Tu6c4E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773506537; c=relaxed/simple; bh=aNW/SvQsvqoGJXuSokC/EAS8h/o0sai/yUenLTWBtuI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GT/vekEWdXh4mtY9I8mkM4sJmIYF2QbZHGdEGmDllOo8gO8SbEIhjPDZFZsrFjom77wJ/+MM/9jRW/gXKeK954ksK/HzpiML5McBmtmDB5H/iwM7K9UVW8hCpTnvEoFkjIJseEaq0T42XVoz1GIMqDLu8c6EiYcBK7ODrKgfp7Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=rowland.harvard.edu; spf=fail smtp.mailfrom=g.harvard.edu; dkim=pass (2048-bit key) header.d=rowland.harvard.edu header.i=@rowland.harvard.edu header.b=e3davlIR; arc=none smtp.client-ip=209.85.160.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=rowland.harvard.edu Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=g.harvard.edu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rowland.harvard.edu header.i=@rowland.harvard.edu header.b="e3davlIR" Received: by mail-qt1-f169.google.com with SMTP id d75a77b69052e-509046c5c7fso41949221cf.1 for ; Sat, 14 Mar 2026 09:42:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rowland.harvard.edu; s=google; t=1773506536; x=1774111336; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=fy06hteiKF+m/zJToPVb5WypJzO6ZJ0i6MwB/Wn9jNc=; b=e3davlIRw0vtox+jEw4C8706Ik5YbO47J3vuOHlPL7W1WTDDVt0DMVWcaBlJmJ+XX/ bQQd8pj4HJxzEeg7vSCT9eB4Pkq9z/j0ExiS4Q+vETE6yDUfAhnkRfLDN+3ILB3zGwV7 c0tWI4xOnJDYNr7Oc6zVu2d+Xs+RKqSUhIOGQuwobJtC2lzylZVT8KJU+TAAuTf6oMB5 TG7LSlr2meFEcqSfyyF1HKXS7W8h9JXbiZZjB5COmIRSpastB8EgwNX4FbDPgqNh+FuU uh+BPIgLVnjgo2EFljrIkWv6c+Q9xoGjOqYDunUL0MuqwZtcn7/saY827ProkHMQ2Jts VdCw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773506536; x=1774111336; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=fy06hteiKF+m/zJToPVb5WypJzO6ZJ0i6MwB/Wn9jNc=; b=Mi0Q6jGTGqqrWz81O0aqXT8b2TmDW1gs55GvfU06y1IhTVvh8Ku1XVHJdwNnQhj+9B 7AlpyG/mE8sp3gS7RjP6o7nIXsA4FrMr2PjyC0tluAqGUNfzgag6Vtm4aVhU84MqwpiB jFX9i5Ou1h5th7l8Lle9xHfjVaoRfqIyoWRQoUgWl28x5ad60rcTB+s0Osu3x8OzF3Fv CHwuORjvShtQmDAYNuZy0aQck7d/IMCwOcfcIxeI911QV1ePIMHONrVRBe1073vz7Bag rcL1387FD08ZEdhXZNF7JQKcH1jZy0u9J/+RpoTrbW0Ptr0H2XOEPxvvRyqUFTqnpbDV Xxmw== X-Forwarded-Encrypted: i=1; AJvYcCWdhUUmIM46XnGVFN7oyiPqFbC3U3+WvfmpnxfCsFW1bsLwuO5WdkAMMrBgXiagHg+v0UcM9sx8CToqdEs=@vger.kernel.org X-Gm-Message-State: AOJu0YxzwPuxUjgxdl3hfROaA1g23Vn1PzohnnyLWmOxrmpEbaYMZv/m ZHsmXgodXGVxLj6wztclQ9RC5zFnZ6njkWx/VUGNWvWrZUYhYQWC74LKOMmmPaOYCw== X-Gm-Gg: ATEYQzzNdIf7sT3ao63WmI1QXLwKuDyWxtqp3ykEAZ1vpbpTsB7VjZAkdQh+vxOTSLv NRtxxVC0h+A4kmXpPHd3/w0CKlfMFNlPDjXuKK9bcKzqsz5Rp7wDvg5Oa2bmwerToeqUBHvrPSu sa1F6C1YjPRaLuZqeZUmahj3HPW6zHdA5qzGOfF7SoJruxQToi+huj7kK0iYNjGKDLEZIBo3x/H gL/m9Af7D1ErVIC8Bxnt++PpAyGrq/KE1yswEBEIm5Y8LSdMIq1Lm7Mtqw49ID0nQtrWVxH+k6l EkU7BkZ8k9P/R3Wqv0vAEe0un/MtXTYYubnv+k7FeehlJ3DZlb17UnH+2RxvY3fma7/pBpTahL2 Cy71n0ZSjJcbnX6XnmWvKrUE5ozYBs+gPbRWWt+1WbDPa/glQy3gBvMKKi5woXciifz+voYamTA fsGBcOAzbOl24/ISBu2/J2lOVo X-Received: by 2002:a05:622a:93:b0:509:4b11:6cf4 with SMTP id d75a77b69052e-50957d51ef9mr100259131cf.5.1773506535458; Sat, 14 Mar 2026 09:42:15 -0700 (PDT) Received: from rowland.harvard.edu ([2601:19b:d01:d210::687c]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5093a14791dsm81733201cf.31.2026.03.14.09.42.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Mar 2026 09:42:14 -0700 (PDT) Date: Sat, 14 Mar 2026 12:42:11 -0400 From: Alan Stern To: syzbot Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [usb?] general protection fault in usb_gadget_udc_reset (4) Message-ID: <041e5d18-6120-48dd-b137-e10020f0c191@rowland.harvard.edu> References: <69b48162.050a0220.36eb34.000f.GAE@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <69b48162.050a0220.36eb34.000f.GAE@google.com> On Fri, Mar 13, 2026 at 02:28:02PM -0700, syzbot wrote: > Hello, > > syzbot has tested the proposed patch and the reproducer did not trigger any issue: > > Reported-by: syzbot+19bed92c97bee999e5db@syzkaller.appspotmail.com > Tested-by: syzbot+19bed92c97bee999e5db@syzkaller.appspotmail.com > > Tested on: > > commit: 65169048 Merge tag 'spi-fix-v7.0-rc2' of git://git.ker.. > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > console output: https://syzkaller.appspot.com/x/log.txt?x=14ab954a580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=2a019678b1a3a692 > dashboard link: https://syzkaller.appspot.com/bug?extid=19bed92c97bee999e5db > compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 > patch: https://syzkaller.appspot.com/x/patch.diff?x=113b1602580000 > > Note: testing is done by a robot and is best-effort only. Just out of curiosity, let's see if this test crashes with only the second change (moving stop_activity()) and not the first (moving the synchronize_irq() emulation). Alan Stern #syz test: upstream 651690480a96 Index: usb-devel/drivers/usb/gadget/udc/dummy_hcd.c =================================================================== --- usb-devel.orig/drivers/usb/gadget/udc/dummy_hcd.c +++ usb-devel/drivers/usb/gadget/udc/dummy_hcd.c @@ -462,8 +462,13 @@ static void set_link_state(struct dummy_ /* Report reset and disconnect events to the driver */ if (dum->ints_enabled && (disconnect || reset)) { - stop_activity(dum); ++dum->callback_usage; + /* + * stop_activity() can drop dum->lock, so it must + * must not come between the dum->ints_enabled test + * and the ++dum->callback_usage. + */ + stop_activity(dum); spin_unlock(&dum->lock); if (reset) usb_gadget_udc_reset(&dum->gadget, dum->driver);