From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8934649482F for ; Thu, 6 Aug 2026 19:36:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786045007; cv=none; b=ejoPh7uocCwJz7ug4qYi4hd9JpXA+prl7S0VfV5FRtKfjHlOzCs9sWHCGrExkgMoyc1quHFJM3M8qJyXHWLpKLhPXrlUcI7jYgA0/rJiwqYjNaRxpN7GqFek2dNoA5QvurayoIsxnIqMK96WxJoThfwtmvJsoS6FIYja7rv+7hw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786045007; c=relaxed/simple; bh=B3QYSXdvc0oqTbovybXloJu6jzJklawFLwgQF9VZllw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=W/QPRCb1YFuN38yI1YT2BXsgqkYsRe+l9O7ZK0cyz4rsjTqEZ0Ig4oFE5s2fznqS8oV7AIynPl0hmJZos0mJwaMzS+mRS9pfJ+/I2o0YEcZ6Y7zb8CTjAkKyK2jztj8+a0PtPPvjmyYGlL1FTS14XBI3xsMYMz6JwQizcpYbx7M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=j74uIjjo; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="j74uIjjo" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6099E153B; Thu, 6 Aug 2026 12:36:39 -0700 (PDT) Received: from [10.211.55.3] (unknown [10.57.68.93]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 969873F632; Thu, 6 Aug 2026 12:36:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1786045003; bh=B3QYSXdvc0oqTbovybXloJu6jzJklawFLwgQF9VZllw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=j74uIjjoAHtxwZflmYnBeXQSz1b5Zd5wQNmJqHWWTCr3HJNi0etJrQ3ZivCvVTiL8 yWCNy5rFTf3uyAKc8dOlVb9qALxGHmgljFM5Rbyby6/4HHXdM5gfcWW5yCkWMXegBl LZSGQ/OMNNaRPynPgHQdF1z/4yLZsWFyNYW6o17A= Message-ID: <0b7702a8-8ffd-468a-b328-755000bd71f2@arm.com> Date: Thu, 6 Aug 2026 20:36:30 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [PATCH v1 1/2] arm_mpam: Fix a NULL pointer dereference on unbinding after an error interrupt To: Andre Przywara Cc: james.morse@arm.com, reinette.chatre@intel.com, fenghuay@nvidia.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, dave.martin@arm.com, will@kernel.org, catalin.marinas@kernel.org References: <20260806144631.2502918-1-ben.horgan@arm.com> <20260806144631.2502918-2-ben.horgan@arm.com> <51f5d369-9491-49cb-957a-dd70ad42ecd6@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: <51f5d369-9491-49cb-957a-dd70ad42ecd6@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Andre, On 8/6/26 16:38, Andre Przywara wrote: > Hi, > > On 8/6/26 16:46, Ben Horgan wrote: >> If a user unbinds an MSC after mpam_disable() has been run in response >> to an error interrupt then a dereference of a NULL pointer occurs as >> mpam_disable() sets the drvdata to NULL. Add an early return to the >> driver >> remove callback to avoid this. > > Yes, I added a very similar patch to my stack yesterday, in response to > a Sashiko complaint. > However I was still calling mpam_free_garbage() at the end, to me it > looks like this is not depending on any MSC? mpam_free_garbage() doesn't depend on any MSC but it won't have any work to do unless something in the driver has been destroyed and mpam_disable() already calls mpam_free_garbage() after it calls the _destroy() functions. Hence, I think it's ok either way. Thanks, Ben > > Cheers, > Andre > >> Fixes: f04046f2577a ("arm_mpam: Add probe/remove for mpam msc driver >> and kbuild boiler plate") >> Signed-off-by: Ben Horgan >> --- >>   drivers/resctrl/mpam_devices.c | 3 +++ >>   1 file changed, 3 insertions(+) >> >> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/ >> mpam_devices.c >> index 2f09f4b78bd3..bc6cc0b5c96b 100644 >> --- a/drivers/resctrl/mpam_devices.c >> +++ b/drivers/resctrl/mpam_devices.c >> @@ -2025,6 +2025,9 @@ static void mpam_msc_drv_remove(struct >> platform_device *pdev) >>   { >>       struct mpam_msc *msc = platform_get_drvdata(pdev); >>   +    if (!msc) >> +        return; >> + >>       mutex_lock(&mpam_list_lock); >>       mpam_msc_destroy(msc); >>       mutex_unlock(&mpam_list_lock); >