From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E56E54334B0 for ; Wed, 12 Aug 2026 15:33:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786548821; cv=none; b=e1HvZXQ6YqqjTdnn/EsK3FtnSOApkn8g2kGGzXfYaTrR8nsyHWRKkSSNXDTx2drLJKxtrV0WTfMxQbgJmKHg5GE2Jk9GXN5avdSZhxqZ6LYsv+hHfqqfcHuE5LaUB9dRx2x8ZYvPRv8A+JN7jmb4rDSrH3eN64O/pMfggI31pTI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786548821; c=relaxed/simple; bh=MshSAdzlkn4ap22AVygvjx0jv1ySj3uhv1qD48JSN/A=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FdR/FIoXRXBIRKJ5FNFveNZqNN1v1/PXlGnZMcHOP39XMXWhhnNOJoX0fxCMcB1g+asFTnNuRP5q4le2nu0TGB9q3tb1JT8rc+2h2LDzWorjabicKDhX95mS8RdbHtEDuK8kUwM5hguGWMdFR5b9qaJqDcpdw9+ord26wHYXG20= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=YBrJLiS+; arc=none smtp.client-ip=209.85.128.70 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="YBrJLiS+" Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4954c2d4081so8709785e9.2 for ; Wed, 12 Aug 2026 08:33:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786548811; x=1787153611; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=eZ+oGpfrYdP0u5dy7mXQ7HlJ9v4mKCq4nCtAk0vOwG8=; b=YBrJLiS+kfOvqfHFrg3TsduISAs+eLb0foc2K/bZrZbX/00k/aFcNppx6C8djtLVen chJTP09C4omu4/+xYCTXGQGtwlmdL2ixL7ESlfo5dtzpUFUJEBWNyDF3+eeiDA0YVfIu kIIZKlE3lFTDA0RcXX9Cy3lbNFhgQkse9tu1PfhpA2FZ+nv5Lv3nXE/cxxjew3XdGqH9 8Hb0SIjHvGEHZ2h1+iziXVLf9EjZUrLYLotiZ+HIzTFtzijK/GWjt3ue+lL+llhTAsfc xQhRSAJZoLkziy1C2M4PHr9+wUQS0j5bkFJSZLI73cUBivpXoUpLOrsTPOan2xPY2Kd4 NP7Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786548811; x=1787153611; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=eZ+oGpfrYdP0u5dy7mXQ7HlJ9v4mKCq4nCtAk0vOwG8=; b=SAqdIUimFCpL8tgJ+AAUp9HksLHvFqBBdMlbN3KxxVEVFVjkWoro9GRpAAOH07EeKD UQ/D6WQVU6U4/XP5rU28o1+y4tUg4/AF80LLxEPjXA8Mw2+znIE3p+PyhEMSzuwzMLtd PgaW9/Pk6y1v4sCsNawp+twmdE2yrSEBe7JuIwF1hMKKduQu7uZ6Z+14Zlql/Yc1On7q 5LRV4IFFtbW4xG36kBgPmAOc6pFFK89StOL3nWkCik5JFQkaDIf3uWUsRB7n/fMBXl+B qn0v+AAwXflSM11w/K+9/5ToL5WtGq/LlcODKgppiZoD3ffAvnl7y+JdG8G0MfmqknWp zpSw== X-Forwarded-Encrypted: i=1; AHgh+RoWHYYT2AxN/tibBxKQqyr8Y0dL3fqiKKF9kR6CB5+j9IAhvPvC3Cq8DweT74oqDRsQC6FZ+vUdmHFO15O2d9AT/fc=@vger.kernel.org X-Gm-Message-State: AOJu0Yz8oMzmCCo6JFoUrFXhsWio05si6Lg21WfwosOon8Oh/oY+DV7T 63FJmFz3vJzQ4+sHRfoDUzJ+i5k4uuo2JIDdhgX15nNFafEuJFIuUZhWmIHvq/fyuqxgKzVpMJ3 p00fVjC8g5KR3whC5HpRnsg== X-Received: from wmi18.prod.google.com ([2002:a05:600c:212:b0:495:6708:efe5]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:3b17:b0:497:ff73:68d5 with SMTP id 5b1f17b1804b1-4997bf7d7ffmr73532505e9.0.1786548811300; Wed, 12 Aug 2026 08:33:31 -0700 (PDT) Date: Wed, 12 Aug 2026 16:33:05 +0100 In-Reply-To: <20260812153311.2328812-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260812153311.2328812-1-vdonnefort@google.com> X-Mailer: git-send-email 2.55.0.691.gc56d675ccc-goog Message-ID: <20260812153311.2328812-5-vdonnefort@google.com> Subject: [PATCH v4 4/9] ring-buffer: Fix subbuf resize race in ring_buffer_alloc_read_page() From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, linux-kernel@vger.kernel.org, Vincent Donnefort , Sashiko Content-Type: text/plain; charset="UTF-8" ring_buffer_alloc_read_page() is racy with ring_buffer_subbuf_order_set, it can allocate a reader page with an outdated order. This isn't a big issue, the user can still re-allocate a new reader page and try again. However, what is more problematic is if the value of subbuf_order changes in the middle of ring_buffer_alloc_read_page(). In that case, bpage->order might not match the actual allocated memory. Use bpage->order for the allocation to prevent this race. Fixes: bce761d75745 ("ring-buffer: Read and write to ring buffers with custom sub buffer size") Reported-by: Sashiko Signed-off-by: Vincent Donnefort diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 97449423d3a6..94552a433228 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -7018,7 +7018,7 @@ ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu) if (bpage->data) { rb_init_data_page(bpage->data); } else { - bpage->data = alloc_cpu_data(cpu, cpu_buffer->buffer->subbuf_order); + bpage->data = alloc_cpu_data(cpu, bpage->order); if (!bpage->data) { kfree(bpage); return ERR_PTR(-ENOMEM); -- 2.55.0.691.gc56d675ccc-goog