From patchwork Thu Oct 3 14:49:25 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13821114 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 E6016126C13; Thu, 3 Oct 2024 14:48:32 +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=1727966913; cv=none; b=ng9zOvSiI/A+N1a0wMsFXIdBGACl5X3TGirBz6tF9QyqgNZEC+6RYp19vhQR58keXsSMQvo2UPl3x+8Dg8g9cubuoKXaQrD78KYQ0rl6xrur0labCbaUCo+eKR0XyVpChDrju98565rkiXmcDXaErmn9qeLot9N4pJR++/GNbco= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727966913; c=relaxed/simple; bh=9H1UCUJdO03zoRskdQul88BnU5jqtiSwZBcVv5KNzmI=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=RyeE378f4DqEJoOgvT1dIajrlp8NXfly5f76dJ2sdxntFpHGpEkwci0fGqcpGXMifBMVnvMviOsXZYAmG7cX00pFT+T12aQki/nq/kxBfngGug2VlbOxaxBgYwAmLeFhON3z80jDqcfP8UoHVfMvtgUrOHQgb5yKLjd0LIE4kqA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id B195FC4CEC5; Thu, 3 Oct 2024 14:48:31 +0000 (UTC) Date: Thu, 3 Oct 2024 10:49:25 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , Alison Schofield Subject: [PATCH] tracing: Fix trace_check_vprintf() when tp_printk is used Message-ID: <20241003104925.4e1b1fd9@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Steven Rostedt When the tp_printk kernel command line is used, the trace events go directly to printk(). It is still checked via the trace_check_vprintf() function to make sure the pointers of the trace event are legit. The addition of reading buffers from previous boots required adding a delta between the addresses of the previous boot and the current boot so that the pointers in the old buffer can still be used. But this required adding a trace_array pointer to acquire the delta offsets. The tp_printk code does not provide a trace_array (tr) pointer, so when the offsets were examined, a NULL pointer dereference happened and the kernel crashed. If the trace_array does not exist, just default the delta offsets to zero, as that also means the trace event is not being read from a previous boot. Link: https://lore.kernel.org/all/Zv3z5UsG_jsO9_Tb@aschofie-mobl2.lan/ Reported-by: Alison Schofield Fixes: 07714b4bb3f98 ("tracing: Handle old buffer mappings for event strings and functions") Signed-off-by: Steven Rostedt (Google) Tested-by: Alison Schofield --- kernel/trace/trace.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index c01375adc471..1c69ca1f1088 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3697,8 +3697,8 @@ static void test_can_verify(void) void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, va_list ap) { - long text_delta = iter->tr->text_delta; - long data_delta = iter->tr->data_delta; + long text_delta = 0; + long data_delta = 0; const char *p = fmt; const char *str; bool good; @@ -3710,6 +3710,17 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, if (static_branch_unlikely(&trace_no_verify)) goto print; + /* + * When the kernel is booted with the tp_printk command line + * parameter, trace events go directly through to printk(). + * It also is checked by this function, but it does not + * have an associated trace_array (tr) for it. + */ + if (iter->tr) { + text_delta = iter->tr->text_delta; + data_delta = iter->tr->data_delta; + } + /* Don't bother checking when doing a ftrace_dump() */ if (iter->fmt == static_fmt_buf) goto print;