From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CF33936403B; Fri, 8 May 2026 22:12:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778278359; cv=none; b=bph2/98lEkH7MTis7bViJwCtsd+MT4ZeRz4gdlkncUx7qO2TGB6uq82KllavY6baxY/ZR5uXYNzEOFGpNWKqTVGm5/rPpC5ADgm0Zy5vlYUc1/4FNq7ElJmQnkzIsegQNRJkgYm/1VFvmeAtRdMZWomr/S/6Le+D7UKSR2MSweg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778278359; c=relaxed/simple; bh=EXFu3dbPq+W4HjNloEeAKnwcJiIEWBNLUBj9vuURyfI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=W1ziW0CNrSN+x7vhoDQN0jlq9D30AMlX4NblMjzH6v18jDJ+vTIWfXkRk8HHGtWYaXQCXxksdk0b0ySH6u7omppHzl/MvklnIWiJBSaMo2ooF39ENoLFMtJN5iPA8wY2xTUDhnlagWyv+GUtFCshpBKG9NKxKOBs5DErhqCcXYM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CnlO75o9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CnlO75o9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 903C1C2BCB0; Fri, 8 May 2026 22:12:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778278358; bh=EXFu3dbPq+W4HjNloEeAKnwcJiIEWBNLUBj9vuURyfI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=CnlO75o9EKo2lfd0L5d5WAEyAgYxUb+JcqBT2DLKUZslcrBS1Z2chmutOVtCGiXBE g6Bk/wLinZBJt1VI3jn3p76vT5/MQxoVUCUaY0wqP5vbPSBcXPQvGUd8rm1AwpNg33 W+Kbk+HOhz81vkQZsFt1U5QVBZ5qfnS8l7gsWB9Z4ot1fkFFPQzyKRvwTfSGDd+hAu XKWXjO+pu9JDmrhdEsHmygwe3GliwZGXhxFNU++0U/P1rcllnRQmKXxT/tCAAmhc5Q M8a/OhbEZOgmRp0nWL72ydShelw3XzeGx+ifhlkgXkbRJf1BMwhSguCZiO70/A93af b/9XEgob0eYrw== Date: Fri, 8 May 2026 15:12:37 -0700 From: Jakub Kicinski To: Marc Kleine-Budde Cc: netdev@vger.kernel.org, davem@davemloft.net, linux-can@vger.kernel.org, kernel@pengutronix.de, Lee Jones , Oliver Hartkopp Subject: Re: [PATCH net 2/6] can: bcm: prevent thrtimer UAF in rx path by checking RX_NO_AUTOTIMER Message-ID: <20260508151237.7d0a9105@kernel.org> In-Reply-To: <20260507112321.439968-3-mkl@pengutronix.de> References: <20260507112321.439968-1-mkl@pengutronix.de> <20260507112321.439968-3-mkl@pengutronix.de> Precedence: bulk X-Mailing-List: linux-can@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 7 May 2026 10:22:24 +0200 Marc Kleine-Budde wrote: > Commit f1b4e32aca08 ("can: bcm: use call_rcu() instead of costly > synchronize_rcu()") removed the synchronize_rcu() call from > bcm_delete_rx_op() and introduced the RX_NO_AUTOTIMER flag to prevent > timers from being rearmed during deletion. However, it only applied > this check to op->timer via bcm_rx_starttimer(). All AIs point out this is insufficient: reader (bcm_rx_handler, RCU) | writer (bcm_delete_rx_op) -----------------------------+------------------------------- test op->flags (no AUTOTIMER)| | op->flags |= RX_NO_AUTOTIMER | bcm_remove_op() | hrtimer_cancel(&op->thrtimer) | /* not armed: no-op */ | call_rcu(bcm_free_op_rcu) hrtimer_start(&op->thrtimer) | return from RCU section | | grace period elapses | bcm_free_op_rcu() -> kfree(op) thrtimer fires | bcm_rx_thr_handler(op) | <-- UAF