From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 ED81346EC8F; Fri, 14 Aug 2026 12:41:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786711290; cv=none; b=G0cOGdz5/NTh0voHuLu4IjiyckL5RFt0WhVLlVFtarVSod6F6elup5LX3Gj/Ihlq/8BVeG2OlKwyjlZwEcZJ9d64WKZ0KZ1QSgyPbIScWln8aSIyeF/wwtVE6fzQ8KPWG4Nyn0fmX5QUtiTNnJsFElzJUXbPC/n8gvcGPLz1Ll0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786711290; c=relaxed/simple; bh=csj+y7b87J57izW7dshInivp64LxKu4YFyOL3Nz+XhE=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=GWA74kAuZLjv9hAr6jY/jk13ylLWPl/iMR4ctWgFlA4IG6zDhOXMoYhIkXktCd6SdifnI8L+04MmDjLdddFxdlrc1t4uFzk5dCuXQgJvPiT7MvQzspmVpl+zRLRHgxRwT5mf+bEc0FkB6ncOt8cC70kPnhAk23705hCBiJk2KmE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PCLb+bbb; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PCLb+bbb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E977F1F00ACF; Fri, 14 Aug 2026 12:41:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786711284; bh=CDKIlCxcHcHVQcLzlXr/2oBd2JZPxlPkIoB88zc/hVY=; h=Date:From:To:Cc:Subject:References; b=PCLb+bbbeyz8Xe0mXoEgTeyXO5LEvKutrU5AL/9/qMWnNZrMKya3RTboD9kFZgrey bAZG2KITSUtNRs4IoPqZfDeP2ciyDG5Y/7r1m2XISbVtTd7aFcKhR+TxjvQUfu8SlV flpLxUD+CQCmbOwoji5QFUwqjTqu83/Zk5jzcPq1AebVCeUXnnNGtRBG9FYWFCsNJR SL8TvLTfcElhX9sgrY00KGy4W9Qo5770jj1/uIJG3yqer1Px/baNgm5wNOnOdeZLJw 691/Xm1f1mLCz4Ya8J5fTRmBeoLpHA0VTwQy3wO6f/9uSo2SBfWw95e1+j6SK2R/pg b7hpHiVckMMTg== Received: from rostedt by gandalf with local (Exim 4.99.4) (envelope-from ) id 1wurEE-00000003zmm-1q5W; Fri, 14 Aug 2026 08:41:42 -0400 Message-ID: <20260814124142.300131278@kernel.org> User-Agent: quilt/0.69 Date: Fri, 14 Aug 2026 08:41:29 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, Sashiko , Vincent Donnefort Subject: [for-next][PATCH 6/9] ring-buffer: Fix subbuf resize race with ring_buffer_alloc_read_page() References: <20260814124123.133362396@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: Vincent Donnefort 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. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260813131152.3589632-6-vdonnefort@google.com Fixes: bce761d75745 ("ring-buffer: Read and write to ring buffers with custom sub buffer size") Reported-by: Sashiko Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index e436793ed5c1..796c10319d6a 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); -- 2.53.0