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 1C3E6128816 for ; Thu, 16 Oct 2025 01:31:47 +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=1760578308; cv=none; b=X0OWoMfIw0iqOIpJCqfGzLSt6Xb2wfl3v/cWWfcU2KGb5b7H9WVLcp884Tl8uzUNKYxVsmTiu45JK5x/P/VHVkIDWdbRzyOAujffTkeH1R5AITwCu+rcneQwka0nuDQ8UVx/l/zbn+y/hP4yTFSMkokruHmVvN4R2c5PZZQJrK8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760578308; c=relaxed/simple; bh=/O+KvSK6ZNqk67j+pEivLfHqGMLjOhJDGdzZAoQuJiY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rT3farg52CviZMTRhL3oxDGxGFr9gYmxyO2s66KsZb/bFwYXrpa30rPmERZGuMLHOhNzuJNLUWoH8+YtgqsBjI1VKwj/RyZ18FBctBByB79yzCHR7JhQsQuG8iKtqTT6/N53epDs0xQbrEYyWhBXEiSpi8sYm0AeM+6yLr7Ap4U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TWxdpGo/; 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="TWxdpGo/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0820EC4CEF8; Thu, 16 Oct 2025 01:31:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760578307; bh=/O+KvSK6ZNqk67j+pEivLfHqGMLjOhJDGdzZAoQuJiY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TWxdpGo/41sQFmS81AfMeAikAKm9lumHWc/hanoWXxlraj0VNDBeNLuuE972rWZI6 436IeJ765rZj1LsjWtS7oA6ZiIDZ0WotKYqQ3N/aEDmA3lmcdbyJbEgWaI3MVw/fVz eLHiQVLwYz1Si8wGGHxSi7/92jN4CzgR37sf++lb4VxyuvwMa11PDCtSG17yqstN8j f6CidxW83sNBdiJDbrGgR9X8LnSqLMk+GRJGtlHWFOWQK33+cZ+7M3KOUMf1hNZXKa rjo2wzo13F08a5fwKahFZmBGkdfNhMkvQnKMeS4xPKz6E/LWaAqIUtUV44YNQVC7r+ SoONxBDL5nFRA== From: Sasha Levin To: stable@vger.kernel.org Cc: Thomas Gleixner , Boqun Feng , Mathieu Desnoyers , Sasha Levin Subject: [PATCH 6.6.y] rseq: Protect event mask against membarrier IPI Date: Wed, 15 Oct 2025 21:31:44 -0400 Message-ID: <20251016013144.1560902-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025101555-glimpse-gauntlet-5c2a@gregkh> References: <2025101555-glimpse-gauntlet-5c2a@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Thomas Gleixner [ Upstream commit 6eb350a2233100a283f882c023e5ad426d0ed63b ] rseq_need_restart() reads and clears task::rseq_event_mask with preemption disabled to guard against the scheduler. But membarrier() uses an IPI and sets the PREEMPT bit in the event mask from the IPI, which leaves that RMW operation unprotected. Use guard(irq) if CONFIG_MEMBARRIER is enabled to fix that. Fixes: 2a36ab717e8f ("rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ") Signed-off-by: Thomas Gleixner Reviewed-by: Boqun Feng Reviewed-by: Mathieu Desnoyers Cc: stable@vger.kernel.org [ Applied changes to include/linux/sched.h instead of include/linux/rseq.h ] Signed-off-by: Sasha Levin --- include/linux/sched.h | 11 ++++++++--- kernel/rseq.c | 10 +++++----- 2 files changed, 13 insertions(+), 8 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index cb38eee732fd0..9559501236af0 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2343,6 +2343,12 @@ enum rseq_event_mask { RSEQ_EVENT_MIGRATE = (1U << RSEQ_EVENT_MIGRATE_BIT), }; +#ifdef CONFIG_MEMBARRIER +# define RSEQ_EVENT_GUARD irq +#else +# define RSEQ_EVENT_GUARD preempt +#endif + static inline void rseq_set_notify_resume(struct task_struct *t) { if (t->rseq) @@ -2361,9 +2367,8 @@ static inline void rseq_handle_notify_resume(struct ksignal *ksig, static inline void rseq_signal_deliver(struct ksignal *ksig, struct pt_regs *regs) { - preempt_disable(); - __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); - preempt_enable(); + scoped_guard(RSEQ_EVENT_GUARD) + __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); rseq_handle_notify_resume(ksig, regs); } diff --git a/kernel/rseq.c b/kernel/rseq.c index 23894ba8250cf..810005f927d7c 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -255,12 +255,12 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags) /* * Load and clear event mask atomically with respect to - * scheduler preemption. + * scheduler preemption and membarrier IPIs. */ - preempt_disable(); - event_mask = t->rseq_event_mask; - t->rseq_event_mask = 0; - preempt_enable(); + scoped_guard(RSEQ_EVENT_GUARD) { + event_mask = t->rseq_event_mask; + t->rseq_event_mask = 0; + } return !!event_mask; } -- 2.51.0