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=1792498813; b=hmbuNDJQbtvDpjxGPftT0jHd3zAOdZg2E58HHa8lUVE1o9wBEY+kQifplxE+QwWXq6a6 0qdERTOw8eqc4JkYL+XxdwUnh/kzf4hUdi/77Hw97PZj9DA7q6wmV7HtbEjYUWWJHdfXT gjkhhgCks09KyJ772tVYGITXYH7BsYy1a15BG6ECShbYKjsfTK6nbMorWmso/3LqvNxTz hUbP2qcjf+5BClOVVT6r+2CKdLGReeqxIWXXwlLzinlK2UxMjLBKaMCXDma1kltGNO9jc XrJM84Win1EXyDDWSZOfSfTRaBVikud5PPKU+ESwkRnm/ovOOrTh08wjNQ6QxEUQJww== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792498813; h=Received:DKIM-Signature:Received:Message-ID:User-Agent:Date:From:To: Cc:Subject:References:MIME-Version:Content-Type; bh=1bX3LhI/tU8AszsfckVEOh+0Dxk/I+jSEHqnFcRwNcY=; b=Ehb1oMZhMBYdl+Jkk9dwmZOqixLEX6an/1f9g0OyvEhOoM2LRU98Kj4eoSKCbUVT+q3a Hu65GdMxJ1Lplz8i4TGoG09hJgYxCcKyhE56tjzjX+GDXEN+3a+BgEZ+2SLCaWHoYEqOU ZWvBdLn+y9u5xFiuYKI4bYoCIBv5UToqwNSBptfvM7PTEGdvgoUaL5R2Mx/e7R2Zn8tw3 TTmXNnfRt/s96b9JQlhwnc3J6RsQSEHagoVMOAYbKDZMrsPn5PMk8XHz9ZSmVW3IedSay LDY1oz8OrIMsTPJvagk9huta9GaKDwJE7zG7rBxdJxoMxebSIrbCnGq3GHQ5vJdQnMw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XH3TQ+i8; 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 5CF4D606A323; Tue, 20 Oct 2026 12:20:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XH3TQ+i8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 162A41F000CD; Tue, 20 Oct 2026 12:20:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792498812; bh=1bX3LhI/tU8AszsfckVEOh+0Dxk/I+jSEHqnFcRwNcY=; h=Date:From:To:Cc:Subject:References; b=XH3TQ+i8sNvp+f9DNGuM/gQcCTelqL+n7OnRsZ2IuugI3fTa/eP7xaACIin+wgXMa Pfz58xKhT5GJWc7M7H1kt9uybEv5ZCN/aXzc6DV0uMx0o4vKEtlRycU+7hhQiCNqki D1UFbVXgXiTHXpbCWM+1vPqSW//1yuvR0u4NWjaybTEdCgxohyBxHcs8u3ACPkNWW5 EXC2/XO9kZcwqV6t1w/S/0SsO5SrkV1PBOui44DYnbW2pgbMEAk0sg8zZ4wzKAhPFP Vi3/X36pqtl9SmTTy6745sbX/d2DbHhF1RPLTbnsxWiVdY+6//X7YQVXFCrV9QMGwy 7D9FbqDa/5zqw== Received: from rostedt by gandalf with local (Exim 4.100.1) (envelope-from ) id 1xJ8p9-00000001y3N-1qtj; Tue, 20 Oct 2026 08:20:11 -0400 Message-ID: <20261020122011.246739609@kernel.org> User-Agent: quilt/0.69 Date: Tue, 20 Oct 2026 08:20:00 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, Sashiko , Donggeun Yoo , Tom Zanussi Subject: [for-next][PATCH 4/6] tracing: Save the event file instead of the compatible histogram References: <20261020121956.600452831@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: Donggeun Yoo create_field_var_hist() creates a histogram on the matched event to supply a field variable, and records it on the target so it can be torn down later: hist_data = find_compatible_hist(target_hist_data, file); ... /* Save the compatible histogram information */ var_hist->hist_data = hist_data; hist_data is not the histogram it creates. It is one that was already there, whose keys the new one copies. The saved pointer has a single user, unregister_field_var_hists(), which runs when the target is removed: file = hist_data->field_var_hists[i]->hist_data->event_file; find_compatible_hist() matches on keys alone, so it can pick one with no variables of its own. check_var_refs() then returns false and the user can remove it while the target still points at it: BUG: KASAN: slab-use-after-free in event_hist_trigger_free+0x2b2/0x320 Read of size 8 at addr ffff8880093b90e0 by task init/1 Freed by task 1: kfree+0x154/0x420 event_hist_trigger_free+0x1d5/0x320 event_hist_trigger_parse+0x35f3/0x69e0 trigger_process_regex+0x1a6/0x250 Save the event file instead. It is all the dereference ever wanted, and it does not go away when the user removes a trigger. Cc: stable@vger.kernel.org Reported-by: Sashiko Link: https://lore.kernel.org/all/20260914110753.221E61F000FF@smtp.kernel.org/ Link: https://patch.msgid.link/20260914234754.3676905-1-donggeunyoo.kernel@gmail.com Fixes: 02205a6752f2 ("tracing: Add support for 'field variables'") Signed-off-by: Donggeun Yoo Assisted-by: Claude:claude-fable-5 Acked-by: Tom Zanussi Signed-off-by: Steven Rostedt --- kernel/trace/trace_events_hist.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 5527605758cb..42b89171134d 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -557,7 +557,7 @@ struct field_var { }; struct field_var_hist { - struct hist_trigger_data *hist_data; + struct trace_event_file *file; char *cmd; }; @@ -3129,8 +3129,8 @@ create_field_var_hist(struct hist_trigger_data *target_hist_data, return ERR_PTR(-ENOMEM); } - /* Save the compatible histogram information */ - var_hist->hist_data = hist_data; + /* Needed to remove the histogram when the target goes away */ + var_hist->file = file; /* Create the new histogram with our variable */ ret = event_hist_trigger_parse(&trigger_hist_cmd, file, @@ -6362,7 +6362,7 @@ static void unregister_field_var_hists(struct hist_trigger_data *hist_data) int ret; for (i = 0; i < hist_data->n_field_var_hists; i++) { - file = hist_data->field_var_hists[i]->hist_data->event_file; + file = hist_data->field_var_hists[i]->file; cmd = hist_data->field_var_hists[i]->cmd; ret = event_hist_trigger_parse(&trigger_hist_cmd, file, "!hist", "hist", cmd); -- 2.53.0