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 6F104522A for ; Mon, 9 Jun 2025 06:25:03 +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=1749450303; cv=none; b=crNiTFhQvTpP77ImJxRVIVXuuz8WPac6HLtS5shU6z6vJF802C6DFU9rHab7bHul/d4Po4Wd6NDQzJqULN3QxssJ350FJi1rU3ZAqJz9Kfuj+iZlqfUVckY25b1M76yprNIsPUdgoZFBSpAri/A2ybTVjVRw2DqTNhljBiKLxA0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749450303; c=relaxed/simple; bh=FDwySwbWdYzZTdWz+Mo5+rUSNr9zCN4gogJojzE3JTA=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=PjEPY75NyzVz/zhY/kGZ4Vp6sRCwS2jhYjXSIzhxTAWwjkEhrocEKkiOQYW9dkBvGiIjVRMgbFsOGSyapLInHBzf5dPyqa2nKJwp+/Y8NAlVRqpC/jcP6VM5sAPj5k6jWHiDJz6UggLY+Z56IXIHe66vXHpwKcVi5yFKHaGhzrg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R/vydeiJ; 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="R/vydeiJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D446AC4CEEB; Mon, 9 Jun 2025 06:25:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1749450303; bh=FDwySwbWdYzZTdWz+Mo5+rUSNr9zCN4gogJojzE3JTA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=R/vydeiJfwZOn3sKUP6bxIGUubeaBm2Q1aP4g/jq8jrH8+FtfJ93hoSZmoB4xyGxP 7g7mbT2+7jN8690j2CAM93jPo+wQPtx7T9sUxMLgzrSWeclFfLs//2Jaz0iz0iglha pnrrPebsRx20pHW3qUJz1vbDMTjQBqpQw7+B/5f1NFbIexIgjABHpIe39x1J0aMkaG XARUsw5RqJ+iS3FTphSxQB5BvZdqxUYp8KTG5klxbozN19h3b0s5RDETRvegDB1Y0c ikVJQHFQiJBx6T5c2VLqZvIZrno1WGehU6Tb8mBG/ptGpQH8Txk6nHo3QaEDcXFnQG rXwB4NH/uODtw== Date: Mon, 9 Jun 2025 15:25:00 +0900 From: Masami Hiramatsu (Google) To: Dmitry Antipov Cc: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Tzvetomir Stoyanov , linux-trace-kernel@vger.kernel.org, syzbot+05d673e83ec640f0ced9@syzkaller.appspotmail.com Subject: Re: [PATCH v2] ring-buffer: fix buffer locking in ring_buffer_subbuf_order_set() Message-Id: <20250609152500.30f1a34ba10488f568f3a6cc@kernel.org> In-Reply-To: <20250606112242.1510605-1-dmantipov@yandex.ru> References: <20250606065124.07857968@gandalf.local.home> <20250606112242.1510605-1-dmantipov@yandex.ru> X-Mailer: Sylpheed 3.8.0beta1 (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 On Fri, 6 Jun 2025 14:22:42 +0300 Dmitry Antipov wrote: > In 'ring_buffer_subbuf_order_set()', prefer mutex guard over explicit > mutex operations to ensure that the buffer remains locked everywhere > where its innards may be changed, thus preventing per-CPU sub-buffer > lists corruptions and other concurrency-related issues. > > Reported-by: syzbot+05d673e83ec640f0ced9@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=05d673e83ec640f0ced9 > Fixes: f9b94daa542a8 ("ring-buffer: Set new size of the ring buffer sub page") > Signed-off-by: Dmitry Antipov Looks good to me. Reviewed-by: Masami Hiramatsu (Google) Thanks, > --- > v2: use mutex guard as suggested by Steven > --- > kernel/trace/ring_buffer.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index e24509bd0af5..00fc38d70e86 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -6795,7 +6795,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) > old_size = buffer->subbuf_size; > > /* prevent another thread from changing buffer sizes */ > - mutex_lock(&buffer->mutex); > + guard(mutex)(&buffer->mutex); > atomic_inc(&buffer->record_disabled); > > /* Make sure all commits have finished */ > @@ -6900,7 +6900,6 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) > } > > atomic_dec(&buffer->record_disabled); > - mutex_unlock(&buffer->mutex); > > return 0; > > @@ -6909,7 +6908,6 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) > buffer->subbuf_size = old_size; > > atomic_dec(&buffer->record_disabled); > - mutex_unlock(&buffer->mutex); > > for_each_buffer_cpu(buffer, cpu) { > cpu_buffer = buffer->buffers[cpu]; > -- > 2.49.0 > -- Masami Hiramatsu (Google)