From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8363D1D88AC; Thu, 29 Jan 2026 00:46:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769647599; cv=none; b=kb8uqgHjT1UUUuNarYQSirrwRLcKISyt/yh3P311+miBQ17PFku43Cma2VHCXcZJlGmz3EtjQ8qhui/HyxJl51UVzTF1noR4t7d9EnOy5fjsX069InDqn1vGpxaOO+hEAqqgVyN9v3TvIJo1rlab7dGu0J/u2lO1X/N7RoX09GM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769647599; c=relaxed/simple; bh=7Xml+48FylCxkNKMZeTofrrUHZFglxeIWVQKeX3ax44=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=sI+Vut6PCecgv6KqUZ5LUGZlVGebOt/NXgC4MKmyXO5gvAoDpgksdqAAmuMyMef2rT/XhMYEt+wG2rZ1cpslQeB+fQwICugfTfnHLFdx8wJtgdIn4sUp1gR7DGw3vQFBHvUHtJEdK8uXVomUtu7EWoKSFZ5C/t0x06Osp7ZV858= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 372E7BA563; Thu, 29 Jan 2026 00:46:36 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf05.hostedemail.com (Postfix) with ESMTPA id 23DA12000D; Thu, 29 Jan 2026 00:46:34 +0000 (UTC) Date: Wed, 28 Jan 2026 19:46:44 -0500 From: Steven Rostedt To: Daniel Thompson Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Will Deacon , Robin Murphy , linux-arm-kernel@lists.infradead.org, Joerg Roedel Subject: Re: [PATCH v2] iommu: Fix NULL pointer deref when io_page_fault tracepoint fires Message-ID: <20260128194644.0c76eeb3@gandalf.local.home> In-Reply-To: <20260128-iommu-io_page_fault_null_fix-v2-1-de047be6dd3a@riscstar.com> References: <20260128-iommu-io_page_fault_null_fix-v2-1-de047be6dd3a@riscstar.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: zbnrqykkbsctq1xypty1uxryh3hi8pak X-Rspamd-Server: rspamout02 X-Rspamd-Queue-Id: 23DA12000D X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19mNQtqSQkXD3+IliWA9iQPxr0OnT5GTl8= X-HE-Tag: 1769647594-734317 X-HE-Meta: U2FsdGVkX18MOrD3v8VfqWZtxIFDGANwb1LiocAuKBOLEhLP+uqW9c6+dxvNIFq+OEEPdjNlAHmX5fwOoUtV4xD0aXUWrxY5XwNRVli6aznBP9SD2jLx1Z0qHupPrFT2dTPJJ/bHAzElKVWmxv47VqQKG3qyI4PLR9abAohEDCXA3XFkv2sE3RQOVCLkEqKY6Dh2MQEVoo/7nydrv8m6s5ucbEWbvxJFmVU80f1x/PwJARS9FMEXlmBxs6T65y6h33QJYSJvbPLdcPFuaOOO4yHiAqi+05Ckbkb5YVIsGy5BHM67DPr4BgzMRgbG26xbopW6W979+xdtLz+pAgO/Dgz0ZLsy45Vc2k0LIGGBtTtOANTEqIwjvDhUPfOvHuGT8dxOP7YO/thpp/7ZXnGWV17GtGb8VlDxbPoR8TSc7B1lU7bL/XYow29uGStBEyrnCAmfv0kwzXKDPcqeATABVA== Note, event changes go through the maintainer's tree where the events are used. But from a tracing POV: Reviewed-by: Steven Rostedt (Google) -- Steve On Wed, 28 Jan 2026 15:48:01 +0000 Daniel Thompson wrote: > The arm-smmu driver is unable to allocate the blame for a page fault to > a specific device so it calls report_iommu_fault() with the dev argument > set to NULL. Normally this doesn't cause anything catastrophic but on a > system with the io_page_fault tracepoint enabled this results in a NULL > pointer deref (resulting in a fairly spectacular crash on the hardware > I'm currently working on). > > Fix this by adding logic to the tracepoint to safely propagate NULL. > > Fixes: f8f934c180f6 ("iommu/arm-smmu: Add support for driver IOMMU fault handlers") > Signed-off-by: Daniel Thompson > --- > Changes in v2: > - Add a Fixes:. It points to the earliest point I can find where it becomes > possible for the tracepoint to be triggered with dev set to NULL. > - Link to v1: https://lore.kernel.org/r/20260116-iommu-io_page_fault_null_fix-v1-1-6c20c2e62987@riscstar.com > --- > include/trace/events/iommu.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/trace/events/iommu.h b/include/trace/events/iommu.h > index 373007e567cb827458a729b8200bbcc1b7d76912..1315193f13b8812ad4e29e6b0c0c66ca806ce08d 100644 > --- a/include/trace/events/iommu.h > +++ b/include/trace/events/iommu.h > @@ -131,8 +131,8 @@ DECLARE_EVENT_CLASS(iommu_error, > TP_ARGS(dev, iova, flags), > > TP_STRUCT__entry( > - __string(device, dev_name(dev)) > - __string(driver, dev_driver_string(dev)) > + __string(device, dev ? dev_name(dev) : NULL) > + __string(driver, dev ? dev_driver_string(dev) : NULL) > __field(u64, iova) > __field(int, flags) > ), > > --- > base-commit: 0f61b1860cc3f52aef9036d7235ed1f017632193 > change-id: 20260116-iommu-io_page_fault_null_fix-f81b4e8b5423 > > Best regards,