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 AF3433B2FF6; Mon, 23 Mar 2026 14:10:16 +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=1774275016; cv=none; b=VdBcEze3RjRbdER8PDS4v2C7oB6V8ZkQw7ZrPdjOE6af2gy6fe/O29qycX79BXPry5VLS2V3+s5Hg/7Cex6eYSxaqAAvPhmAHIF/AK5mfcHfrRS2kTzHtNPiQRilEebh/w/7Ipe624kgC0YUm+/9AeT4Wspz1vzUw5qnQzcMw7c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774275016; c=relaxed/simple; bh=mmTUF/szwNFwG27eAe8fDFW5Bp8e1hsNtnkNfYh2whc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=F4r5ph+ZnBL/7bjo8gRapHvm9todsHTYxG67sXi5yxXKaVOJEhGtsZDi6LS3dDAkJE/Yw/QWMS3I8mEeE+JevQT2zRzdalENiCp+XkK+hJ2FSoaiY1eNclkdzIVxTEioYBpuGqYDPFjls1pnb4g1JsTu8ufPFIeVv8PrCTLqFbo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VUVNsLeC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VUVNsLeC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C5F3C4CEF7; Mon, 23 Mar 2026 14:10:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774275016; bh=mmTUF/szwNFwG27eAe8fDFW5Bp8e1hsNtnkNfYh2whc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VUVNsLeCUDpj8UVOGT+7I8xdZT4sY76wBVl/sqSMzILk7thTSS/TqMxI5nKSL+UFt gi8v1T0ZpfBq8o/Lai1Szp3u4KsIH+HSmLHknjbI0u+U+ke0Kx6WChloT9J3Tn9hHl NL4/eUVRr+9ExXzpqAWClwebuXXiQJDDqa11+n3Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Masami Hiramatsu , Mathieu Desnoyers , Sasha Levin , "Steven Rostedt (Google)" Subject: [PATCH 6.18 194/212] tracing: Fix trace_marker copy link list updates Date: Mon, 23 Mar 2026 14:46:55 +0100 Message-ID: <20260323134509.857786007@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134503.770111826@linuxfoundation.org> References: <20260323134503.770111826@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Steven Rostedt [ Upstream commit 07183aac4a6828e474f00b37c9d795d0d99e18a7 ] When the "copy_trace_marker" option is enabled for an instance, anything written into /sys/kernel/tracing/trace_marker is also copied into that instances buffer. When the option is set, that instance's trace_array descriptor is added to the marker_copies link list. This list is protected by RCU, as all iterations uses an RCU protected list traversal. When the instance is deleted, all the flags that were enabled are cleared. This also clears the copy_trace_marker flag and removes the trace_array descriptor from the list. The issue is after the flags are called, a direct call to update_marker_trace() is performed to clear the flag. This function returns true if the state of the flag changed and false otherwise. If it returns true here, synchronize_rcu() is called to make sure all readers see that its removed from the list. But since the flag was already cleared, the state does not change and the synchronization is never called, leaving a possible UAF bug. Move the clearing of all flags below the updating of the copy_trace_marker option which then makes sure the synchronization is performed. Also use the flag for checking the state in update_marker_trace() instead of looking at if the list is empty. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://patch.msgid.link/20260318185512.1b6c7db4@gandalf.local.home Fixes: 7b382efd5e8a ("tracing: Allow the top level trace_marker to write into another instances") Reported-by: Sasha Levin Closes: https://lore.kernel.org/all/20260225133122.237275-1-sashal@kernel.org/ Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -569,7 +569,7 @@ static bool update_marker_trace(struct t lockdep_assert_held(&event_mutex); if (enabled) { - if (!list_empty(&tr->marker_list)) + if (tr->trace_flags & TRACE_ITER_COPY_MARKER) return false; list_add_rcu(&tr->marker_list, &marker_copies); @@ -577,10 +577,10 @@ static bool update_marker_trace(struct t return true; } - if (list_empty(&tr->marker_list)) + if (!(tr->trace_flags & TRACE_ITER_COPY_MARKER)) return false; - list_del_init(&tr->marker_list); + list_del_rcu(&tr->marker_list); tr->trace_flags &= ~TRACE_ITER_COPY_MARKER; return true; } @@ -10232,18 +10232,19 @@ static int __remove_instance(struct trac list_del(&tr->list); - /* Disable all the flags that were enabled coming in */ - for (i = 0; i < TRACE_FLAGS_MAX_SIZE; i++) { - if ((1 << i) & ZEROED_TRACE_FLAGS) - set_tracer_flag(tr, 1 << i, 0); - } - if (printk_trace == tr) update_printk_trace(&global_trace); + /* Must be done before disabling all the flags */ if (update_marker_trace(tr, 0)) synchronize_rcu(); + /* Disable all the flags that were enabled coming in */ + for (i = 0; i < TRACE_FLAGS_MAX_SIZE; i++) { + if ((1 << i) & ZEROED_TRACE_FLAGS) + set_tracer_flag(tr, 1 << i, 0); + } + tracing_set_nop(tr); clear_ftrace_function_probes(tr); event_trace_del_tracer(tr);