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=1793207773; b=yB4sojVx/Fz0Wiksyw7lNOxC7klimHEzp2IytbykZGEx6kLxTLt9aGKD/pbckLWYRs9J 3ZVgNKK994Eq1F616Y0TVzit0TvxSQNi8v+BBa7lB4bXKYVrt0xsB22uNPKskUBszLfBq SaBFPVYiQUL9MOrDGOv4ZbWKYcz9mEC29ZdX7Ni82tYnDKX8uQ77W9XMAEoNHU1Z8XYO1 ku+sYbHXtiV8Lv8s7IUx39ALfILS7WWFt6s9A1F9tq6P4gangJjM+sPB2TsmX8h9CLENv mbN3f/42SzWSuzyFH5rkjzDQG96XZ8xAAZ1+3FS1XghCdE0OkGV4dsmoBPRc6YOii7g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793207773; 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=Lu76WtBKHXPuSViSGMXMIt/bsoQ19qFEmOMJecBoWJ8=; b=tizH3TonovrLTNmoHUc+0sbdMib2bjkJT9i0JaHThO8B8VNxVw4yUC1q/DMdPeoa7cSv wnzHLUv8TXZSDhTy6ZNSeQ20WaLJO67iESkymQt1dhExi1fqmvrdHZIILUvFOIZjNPdFz NiIfkXbJmEogZGjNSCOWhifQ5wIQcg0L+ZQ4Yje/4eBK/eCJv7qeFlQX1gT0FIc9VakAV zdjf6hBHMigiwCTwjMYJdWhjkb7PlIdSeeOkbFMplEoipKAhsttNUGeNRn0giIvWfC0h4 LBWplIUIEQhMPVKlxwLfAaO6Ihw7zn5ZuwpUA9LMqcetAqeANGOSi1jiDDk07F/bg9Q== 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=hc8SrPgp; 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 C5679606A31A; Wed, 28 Oct 2026 17:16:12 +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=hc8SrPgp Received: by smtp.kernel.org (Postfix) with ESMTPSA id 230971F01825; Wed, 28 Oct 2026 17:16:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793207772; bh=Lu76WtBKHXPuSViSGMXMIt/bsoQ19qFEmOMJecBoWJ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=hc8SrPgpW8V6/wg12E6hxOeh2x9SDqojUWV9VmDpnejLyraLVoHPQEMnfCOgfgOk4 S/OgV7Gf+Yrqc+IAPdeTgTBKGlQyURM7E4EJN7f5X9RMRONabwa04iMvdtWxjN1MyR 2J1ORST1hslhh4bmRjgbN/yOG/MoiA04RunltPo8= 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 6.12 080/247] ring-buffer: Fix the sub-buffer array base in rb_meta_subbuf_idx() Date: Wed, 28 Oct 2026 17:58:03 +0100 Message-ID: <20261028165949.287551422@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165947.349197979@linuxfoundation.org> References: <20261028165947.349197979@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 6.12-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 @@ -3203,10 +3203,8 @@ 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_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; }