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 1EAD737C92D; Sun, 22 Mar 2026 03:09:34 +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=1774148974; cv=none; b=hHUaowAFXKr/rE/FMz9/bFMUFWfPzlYcUQbrOipmCYHRx0W6UbxpAjPXOdVcKIr0JCQ2r57fjNZ2+1h/3Z1bHRz6QhJzmDo45Wjlayt/TwABpdmRHcdhqckV9T4mE6qH8BEAl2nPzTVacyj1MGSglSdx9d5E/zhhVb5mDSD/l9s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774148974; c=relaxed/simple; bh=qtH6bG4u2QFvuoi0sHppW45t1BcXTOUZnSN9m4ZE0F8=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=Q7My+2b4A3vNv/d7Wlk94A8w2bOLXjLLCDHeam/QB8ZPP6pPLnAS05OpUTBjyNdFn1kIku3pz8iKcc8oUq9E152Z1zTiRCPARK4G1NbmrKtF2NeoHq+KJNRJmdmKlFJBSWPakNEJfzXOLIBPdBK1u+4x/66Y6D4+dHbXYPa5foY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=St4VISp/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="St4VISp/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EFBEEC2BCB7; Sun, 22 Mar 2026 03:09:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774148974; bh=qtH6bG4u2QFvuoi0sHppW45t1BcXTOUZnSN9m4ZE0F8=; h=Date:From:To:Cc:Subject:References:From; b=St4VISp/eESYD9sFLI8+jZcJ+y51aMmXU8RaUbgrIBErHzVXw2bMy04DDTSf8C5qh CiN6Xt8KdWyi3gFjBw5vs6Zmc3oFAcfiZITcDNbSvhwRvrhmFOsFDFQ27yrmKWCOeF lTxveF0SexiCdf5FLt7wXqtF7snosM9BGbOvHyyHznG8FezG78siG3GFBjcACxlZ4X hewim5eoKKFuAzqmkDd5+NZuGlMmWArnWG0J0wnoAT4CSiKOaKtwTJmw/kGyCvHPvo HpXoVov9K/WQDC/ZQTOI6VREFHxUkLoU82eNZDqZq35/dytlqrayR8Su+y5GZS52ly ohWuN9+grUDdg== Received: from rostedt by gandalf with local (Exim 4.99.1) (envelope-from ) id 1w49Cc-0000000B7kH-2AUe; Sat, 21 Mar 2026 23:10:10 -0400 Message-ID: <20260322031010.367354466@kernel.org> User-Agent: quilt/0.69 Date: Sat, 21 Mar 2026 23:09:57 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, Sasha Levin Subject: [for-linus][PATCH 3/5] tracing: Fix trace_marker copy link list updates References: <20260322030954.198361547@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: Steven Rostedt 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) --- kernel/trace/trace.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index bb4a62f4b953..a626211ceb9a 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -555,7 +555,7 @@ static bool update_marker_trace(struct trace_array *tr, int enabled) 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); @@ -563,10 +563,10 @@ static bool update_marker_trace(struct trace_array *tr, int enabled) 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; } @@ -9761,18 +9761,19 @@ static int __remove_instance(struct trace_array *tr) list_del(&tr->list); - /* Disable all the flags that were enabled coming in */ - for (i = 0; i < TRACE_FLAGS_MAX_SIZE; i++) { - if ((1ULL << i) & ZEROED_TRACE_FLAGS) - set_tracer_flag(tr, 1ULL << 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 ((1ULL << i) & ZEROED_TRACE_FLAGS) + set_tracer_flag(tr, 1ULL << i, 0); + } + tracing_set_nop(tr); clear_ftrace_function_probes(tr); event_trace_del_tracer(tr); -- 2.51.0