From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9B69ACEFCE2 for ; Tue, 6 Jan 2026 18:29:41 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4dm07m0bhdz2xPB; Wed, 07 Jan 2026 05:29:40 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=172.105.4.254 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1767724180; cv=none; b=djWJPQpzFgdoaphKKr/zgIkp28nlUF7AKs3eyJ3oCg3+o1ZWjExwKPv0LHXXue2a94mRNngtZH+uyspYrrCRBE9gBX8+kZ1k3hdrH/pGTj715+dNRfSb4OsgyrtxyY+/8AqMaLraSPhmlmByeJUQqtUzOPI7ixlk5lL40MONFpbc6XmZmKzzcQBW0a3eIgF4Pog6gQMAXmHWvREbRKexJVKyojYyW6PCzDBvziXQhIkIj1oe2lnpC+5yXXcd5DOfmoZDu7axKi7w+hqsVPlbDfJsLOuTaI8276c5kkPtJM/c60fKEI4bOMd6y6pWZ/GITYsY2z8rgpCgUXwWa4brmA== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1767724180; c=relaxed/relaxed; bh=C6qFHxqoWBG7IV6u8Cbs7on3ylcj5l0UA0SsRBcTYU4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AjYgSxbjTTVmDB0bAMV+uDv5iG66ga7FOBaGvR7j5AUisWLPTYdmkcdNoSpyNiM2w+uV97VHkHS0fjdgx0dRICeo3Jl/b3cjh0d0ULY7YMxufnhOGdFrIlnArVHA+Z0lXvwz7JEF4JZzEGu7QKMnw8UnysyqUkrklAs/Jy4zBKZieggOiHl7zUZcM9I2f/T4R5dSJx5dIpZt4Bd5HeUioKnibw1TN+bNleuWYcnOnCheUfLnwt73gAjABaKzPVv26HlPadjxSuqMEufCa8tehRP6nOcjLSyG+wPuagsHUUkLv5hpUC2ffuycjXHlctBM0w6ecAyHpCh+O85tRtQTJA== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=SyQv0/FV; dkim-atps=neutral; spf=pass (client-ip=172.105.4.254; helo=tor.source.kernel.org; envelope-from=chleroy@kernel.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.org Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=SyQv0/FV; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=172.105.4.254; helo=tor.source.kernel.org; envelope-from=chleroy@kernel.org; receiver=lists.ozlabs.org) Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4dm07l0kz2z2xLR for ; Wed, 07 Jan 2026 05:29:38 +1100 (AEDT) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 113EB60144; Tue, 6 Jan 2026 18:29:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3793EC116C6; Tue, 6 Jan 2026 18:29:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767724145; bh=viOFB4/yDJPmlUVK9aA8lHxdD5KZeK3qCbk9U703L4E=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SyQv0/FVAuHmLLwaUjLZZIbKRJ0Ehmu9FcOAuL/Te9JbKsrsAcuaCb+Hh5YGxuW6G VkVl8ulqlqE9lEttQE8XxMTMSYEK1D96atzzOY+t6d3yb53OVWzVVs2F2Ptfg7EOAU zeGB/Vs5BjrBO6KddnnwOZJag4OPAytBPKke+X49hvirea36YlOw3RKtTaZ/hhidQ8 Rn1333x7VB3pOwB+julHkI3YIxt7CFmNBtmk40LsDlrG0YeDPkkm45Pe7DCpPKl1hw WOFU9KcQzE2WHLhzt+ILx6VR9mPYNNg+IHyLj4uk6TMckdb/PicweYTbTqAwAu5Mp3 yFArfhjPITKdA== Message-ID: Date: Tue, 6 Jan 2026 19:29:00 +0100 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] soc: fsl: qbman: fix race condition in qman_destroy_fq To: Richard Genoud , Marco Crivellari , Kees Cook , Roy Pledge , Claudiu Manoil , Scott Wood Cc: Thomas Petazzoni , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20251223072549.397625-1-richard.genoud@bootlin.com> Content-Language: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: <20251223072549.397625-1-richard.genoud@bootlin.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 23/12/2025 à 08:25, Richard Genoud a écrit : > [Vous ne recevez pas souvent de courriers de richard.genoud@bootlin.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] > > When QMAN_FQ_FLAG_DYNAMIC_FQID is set, there's a race condition between > fq_table[fq->idx] state and freeing/allocating from the pool and > WARN_ON(fq_table[fq->idx]) in qman_create_fq() gets triggered. > > Indeed, we can have: > Thread A Thread B > qman_destroy_fq() qman_create_fq() > qman_release_fqid() > qman_shutdown_fq() > gen_pool_free() > -- At this point, the fqid is available again -- > qman_alloc_fqid() > -- so, we can get the just-freed fqid in thread B -- > fq->fqid = fqid; > fq->idx = fqid * 2; > WARN_ON(fq_table[fq->idx]); > fq_table[fq->idx] = fq; > fq_table[fq->idx] = NULL; > > And adding some logs between qman_release_fqid() and > fq_table[fq->idx] = NULL makes the WARN_ON() trigger a lot more. > > To prevent that, ensure that fq_table[fq->idx] is set to NULL before > gen_pool_free() is called by using smp_wmb(). You dismantle/reimplement qman_release_fqid(). Is that the only possible approach ? Isn't it possible to just clear fq_table[fq->idx] _before_ calling qman_release_fqid() ? > > Fixes: c535e923bb97 ("soc/fsl: Introduce DPAA 1.x QMan device driver") > Signed-off-by: Richard Genoud > --- > drivers/soc/fsl/qbman/qman.c | 24 ++++++++++++++++++++++-- > 1 file changed, 22 insertions(+), 2 deletions(-) > > NB: I'm not 100% sure of the need of a barrier here, since even without > it, the WARN_ON() wasn't triggered any more. > > diff --git a/drivers/soc/fsl/qbman/qman.c b/drivers/soc/fsl/qbman/qman.c > index 6b392b3ad4b1..39a3e7aab6ff 100644 > --- a/drivers/soc/fsl/qbman/qman.c > +++ b/drivers/soc/fsl/qbman/qman.c > @@ -1827,6 +1827,8 @@ EXPORT_SYMBOL(qman_create_fq); > > void qman_destroy_fq(struct qman_fq *fq) > { > + int leaked; > + > /* > * We don't need to lock the FQ as it is a pre-condition that the FQ be > * quiesced. Instead, run some checks. > @@ -1834,11 +1836,29 @@ void qman_destroy_fq(struct qman_fq *fq) > switch (fq->state) { > case qman_fq_state_parked: > case qman_fq_state_oos: > - if (fq_isset(fq, QMAN_FQ_FLAG_DYNAMIC_FQID)) > - qman_release_fqid(fq->fqid); > + /* > + * There's a race condition here on releasing the fqid, > + * setting the fq_table to NULL, and freeing the fqid. > + * To prevent it, this order should be respected: > + */ > + if (fq_isset(fq, QMAN_FQ_FLAG_DYNAMIC_FQID)) { > + leaked = qman_shutdown_fq(fq->fqid); > + if (leaked) > + pr_debug("FQID %d leaked\n", fq->fqid); > + } > > DPAA_ASSERT(fq_table[fq->idx]); > fq_table[fq->idx] = NULL; > + > + if (fq_isset(fq, QMAN_FQ_FLAG_DYNAMIC_FQID) && !leaked) { > + /* > + * fq_table[fq->idx] should be set to null before > + * freeing fq->fqid otherwise it could by allocated by > + * qman_alloc_fqid() while still being !NULL > + */ > + smp_wmb(); > + gen_pool_free(qm_fqalloc, fq->fqid | DPAA_GENALLOC_OFF, 1); > + } > return; > default: > break; > > base-commit: 9448598b22c50c8a5bb77a9103e2d49f134c9578 > -- > 2.47.3 >