From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792774736; b=4yCwkXIO2EieUNlXU7qd7WJobve27AubMXnD194iPNo+G7lniytCX7+ty9iYeLdrxGnh YZ0s17f6sSN1bNCMzKXtQ1uiFBFc2RKfWIjX2vwqhwahv8kn9DXm3nGMF/rkWfHsantAK PmgVzg47iCpMvJK6ov9UH5ifgc8bhSiDwJGjMfmRTMcIcbywSjoL8LlWEJPuD8C1u4fuM kVJOoWFzNz6vC1Qkd4XR/uiyoQRfq2MuBju8vdNTlNsQgRcJBjR5X7u8KbYtzdrMtYDrw DPAvBzztOqjhmmMsDR++9ncri7AyhEIj5IFHetUHmFaW3ImncxjqTDw/K71tQHzYJTA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792774736; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=FouEzS6SAWEgprPKgjrvb96ovcxDEbrWVAyjxpoOVdI=; b=cpAfHzz21lE+t+8XEi0ad2/If/FN/yp5QghRr6ho9kCW+BS4lDqyq3hg2Lm4Sx6Yxt8H szBuOH2cc4G1Y1jcmdRqTG7iwY+lhw2xFzhpHoXCfqHIpQoNIkXlRhz4b7/ivuzqmzkJv LRnsptNNVG2pDi+vpvMJkUGA4CuIFIkXkKE2BZlMNFogIo4EU8sOflmSXSxQ/nTugYjJG yf6mKwksncWx1z7dasbnCZljUgYiyBjvjjUnzJSDU3QiAc/cptEMV5aDDfGdYHfixIOpi BKKLqg+L5SWqhPvQIPSguub9JEvrYVrbZuZx2uociuBVcqWDK/ntety5zypVRSJBmwg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ysI3KjGI; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8A4B6606A31A; Fri, 23 Oct 2026 16:58:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ysI3KjGI Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB8BF1F01828; Fri, 23 Oct 2026 16:58:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792774736; bh=FouEzS6SAWEgprPKgjrvb96ovcxDEbrWVAyjxpoOVdI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ysI3KjGITmJPakBJUxg6+5LH1EdDWmq9RfwllEYzBN5n8d3AIAZnhQI+zYJuRcUU4 AzkGb0b9b7GyYEz9QXVubUbgVf4JpAWwb8s27Tx6thT9S1TThKF6YltldeWN28Y7Sz JU9ogYKcKkHP11OrJADxxyTxEJlNWrmBqdH/l0+c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Donggeun Yoo , Vincent Donnefort , "Masami Hiramatsu (Google)" , Steven Rostedt Subject: [PATCH 7.2 142/242] ring-buffer: Fix the sub-buffer array base in rb_meta_subbuf_idx() Date: Fri, 23 Oct 2026 18:39:44 +0200 Message-ID: <20261023163717.138208747@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261023163713.816071858@linuxfoundation.org> References: <20261023163713.816071858@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Donggeun Yoo commit 25132363c723afc39aace8b098f547ab4a0ea759 upstream. On a persistent ring buffer, rb_meta_subbuf_idx() can return an index one sub-buffer too high. rb_setup_ids_meta_page() then fills subbuf_ids[] shifted by one and leaves subbuf_ids[0] NULL, which __rb_map_vma() dereferences when userspace maps trace_pipe_raw. rb_update_meta_reader() writes two such indices into meta->buffers[], which rb_cpu_meta_valid() would reject on the next boot, discarding the previous boot's trace. A CPU's sub-buffer array starts after its meta header and the nr_subbufs integers that follow, aligned up to a sub-buffer. rb_meta_subbuf_idx() inverts that calculation but skips only the integers, not the header, so its base is one sub-buffer low whenever the omitted header size crosses the alignment boundary. Invert the calculation with rb_subbufs_from_meta() rather than repeating it. rb_range_buffer() maps an index back to an address through the same helper, so the two directions can no longer disagree. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260918071507.1019251-1-donggeunyoo.kernel@gmail.com Fixes: b14d032973d4 ("ring-buffer: Add ring_buffer_meta data") Signed-off-by: Donggeun Yoo Reviewed-by: Vincent Donnefort Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- kernel/trace/ring_buffer.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3616,10 +3616,8 @@ static void rb_inc_iter(struct ring_buff /* Return the index into the sub-buffers for a given sub-buffer */ static int rb_meta_subbuf_idx(struct ring_buffer_cpu_meta *meta, void *subbuf) { - void *subbuf_array; + void *subbuf_array = rb_subbufs_from_meta(meta); - subbuf_array = (void *)meta + sizeof(int) * meta->nr_subbufs; - subbuf_array = (void *)ALIGN((unsigned long)subbuf_array, meta->subbuf_size); return (subbuf - subbuf_array) / meta->subbuf_size; }