From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EFEA04279E9; Tue, 28 Jul 2026 12:58:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785243514; cv=none; b=btWxiSZBeGnr4mxqmvk3lVKj45W2+4sslf/jyrM8GgER4u2PD3M2vNMlZjpFsjIcki427fmjUnl3jJLBvMzJMxqZh02M8JdseqPMWaH8mZ2jCJnAMGePmwrZVN3b+PDJm+w6i9EmWwhQs+iUFSSWQ/WsB5XJlWOqVvzkhiPfUds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785243514; c=relaxed/simple; bh=iM5zPdKoP4R2a4bIeAg9U2JW7uEG0VarSVcZuUfwBD4=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=F9KUbV/FOviYjJcgDHG67vBORRoR6OrDKvs5IFdZVsDVedi0g2VxR9R9bdKIhUNi6rqmx8VLGy3aWAMOdTI5skYrFwZfvY8aTFFiDftdOb1dmzMC4KxjvmoRzyXHlJxI6rRcIDfit2HkwsGR7dTaDliGTXCeSq0HpCYSJI5xMB0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=l2mvFaHR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="l2mvFaHR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E5691F00AC4; Tue, 28 Jul 2026 12:58:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785243512; bh=Q3+5PLC6tuiR15k7Ir1miK99OsvsI6f+wZcxr7t+LYo=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=l2mvFaHRJs865B7pMSUiBOmrM2AzV8ln1/PWvJoJwtl0mGNvqcX65rQFKQwI1MnjY ADMked79QJnuVW56zKrfTnZih/lRnJUt1OLs4JW/bugtfOWoNKxQbO25OLYPxZjk5p EKqPs379vuvR6F2ioMTfJ6XzbcM9dl4XOL6o1Ju7hA9vYeEy03Ga1mWhKMUcASrT7E JTzs+fA07xtYwrEFwOncw6iRGXbTZslYDd96/p+iopgWEhe14SPTVH6ue8AqmLRvGX kDSfZtgYZkAz7dUjo7B1XkSMMvJQDbOLni0nZtlMLjipduELfoeJMfRRkxAJTohTIh w3hz1uYOAwNzg== Date: Tue, 28 Jul 2026 21:58:29 +0900 From: Masami Hiramatsu (Google) To: Raushan Patel Cc: Steven Rostedt , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] tracing/probes: Reject $arg0 in meta argument expansion Message-Id: <20260728215829.42b08c74e29665f295f1fdc7@kernel.org> In-Reply-To: <20260724054435.146279-1-raushan.jhon@gmail.com> References: <20260724054435.146279-1-raushan.jhon@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 24 Jul 2026 11:14:35 +0530 Raushan Patel wrote: > traceprobe_expand_meta_args() parses $argN with simple_strtoul() and > calls sprint_nth_btf_arg(n - 1, ...). For $arg0, n is 0 so the index is > -1. Because ctx->nr_params is signed, the "idx >= nr_params" guard in > sprint_nth_btf_arg() does not catch the negative index, and > ctx->params[-1].name_off is read out of bounds. > > The normal per-argument path (parse_probe_vars()) already rejects > $arg0 via its argument-number check, but meta-argument expansion runs > before per-argument parsing and substitutes the value first, bypassing > that check. > > Reject $arg0 explicitly during expansion. Good catch! Let me pick this. Thanks! > > Fixes: 18b1e870a496 ("tracing/probes: Add $arg* meta argument for all function args") > Signed-off-by: Raushan Patel > --- > kernel/trace/trace_probe.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > index 506e6037e163..c8fd9b946f44 100644 > --- a/kernel/trace/trace_probe.c > +++ b/kernel/trace/trace_probe.c > @@ -1901,7 +1901,11 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], > trace_probe_log_err(0, BAD_VAR); > return ERR_PTR(-ENOENT); > } > - /* Note: $argN starts from $arg1 */ > + /* Note: $argN starts from $arg1, so $arg0 is invalid. */ > + if (n == 0) { > + trace_probe_log_err(0, BAD_ARG_NUM); > + return ERR_PTR(-EINVAL); > + } > ret = sprint_nth_btf_arg(n - 1, type, buf + used, > bufsize - used, ctx); > if (ret < 0) > -- > 2.53.0 > -- Masami Hiramatsu (Google)