From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) (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 4D2B735C68B for ; Fri, 28 Aug 2026 17:48:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787939334; cv=none; b=Zalf9/ZCoOv82H4tddksBjp5i2WLUlKXsbeTZxLa4ZEukw9r9Rtnvec94/KwL4rmYdXZgwfwjqMyXWDjo22E5HNvUNOna0olqyua9kyKaV3qhCqn4PQjOyv0hKJYsZIVgl+rBk0rQMd7o5SSC6gCrYlV4XdvlyNwYqLlpafWCUM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787939334; c=relaxed/simple; bh=aLkabJqgZ7sedDtk/fVfc6fwzp8mf9Hb8VpBmwZ2sAE=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=bvZ9YxSQi92j3/nOaHlnTDg8mJgL4VUwZ3nIJF3V84M1kL08FGkOgL/QA9zX9ZXctjZE3mvCLpkwK1xB2tQT0mBztS/J+qoCdhUegi8CkXNe5qfOjwah2jGeO+hM5q/bXFuQOMeYIRXEk9VxSPyIn/3bDG1bo5+ULG7eZqQr0No= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; dkim=pass (1024-bit key) header.d=goodmis.org header.i=@goodmis.org header.b=MSqE6fIW; arc=none smtp.client-ip=216.40.44.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=goodmis.org header.i=@goodmis.org header.b="MSqE6fIW" Received: from omf01.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id CFDCE80521; Fri, 28 Aug 2026 17:48:50 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf01.hostedemail.com (Postfix) with ESMTPA id 21D0A6000C; Fri, 28 Aug 2026 17:48:49 +0000 (UTC) Date: Fri, 28 Aug 2026 13:49:38 -0400 From: Steven Rostedt To: Breno Leitao Cc: mark.rutland@arm.com, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: ftrace: UAF in ftrace_regex_open() on a removed tracing instance Message-ID: <20260828134938.1a6f8c4f@gandalf.local.home> In-Reply-To: <20260828123430.22d43b44@gandalf.local.home> References: <20260828104201.21aa9d08@gandalf.local.home> <20260828123430.22d43b44@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 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: ca9ubcsizyfew1qsokh9k4phfp5e8fhk X-Rspamd-Server: rspamout04 X-Rspamd-Queue-Id: 21D0A6000C X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18UINrTRcI26prbVJTbj2Nr3x1oUMUsz9M= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=goodmis.org; h=date:from:to:cc:subject:message-id:in-reply-to:references:mime-version:content-type:content-transfer-encoding; s=dkim1; bh=mrPkrNQ3/o1waqcSm8wt1bhuzanyHzue5dSeCpgqc2A=; b=MSqE6fIWzNJqQw1ZbqlYAZoGOf6Mb/bkJYa6hpRm342XdHEWoCgJYQZTYYdp7mPy/vWU5nUggRE+5asOzw98lgsoVjHa714fDwQ4CTbdz3fiRjlNBsJPmvDuc7kfRV1xwPoNFiDW2HBZQvawQWFxSOSSxCIKB/Qqxwmj9vonmbM= X-HE-Tag: 1787939329-327006 X-HE-Meta: U2FsdGVkX1/qLlavYHPCdSXHjUDhVZse5VPs4cIwbIu9800bfBOA0XS1OoVB85gzswfApL38EyX/D9gL2Hvy4FHlU9q1fBvW4258dBcXio67Lw10QE7klngPmY0PNslALRpZJ5rKbXFjGDTskQRZWzIsslAcmAjc38JHDJFrOTAU8V+/XJAIYZlr11I2ibIHRlQz3/tWBBA/WHXmaqo0QHibn6kz58WyTeCtdT5onKrYROsMBuGdmUXR+/nPtJxMGLdLlkKmiZ8lna5J3q7BZzbBRFD4QoJXysDtCz3HO36lg84XlSm64vBkD687c7mETI1NZ7DvlQ2iI+4wVODZn02OF98sl1llUDUenMvBtqvY+jxN5XfIoiIj9JqljFN6 On Fri, 28 Aug 2026 12:34:52 -0400 Steven Rostedt wrote: > > trace_create_file("set_ftrace_filter", TRACE_MODE_WRITE, parent, > > - ops, &ftrace_filter_fops); > > + ops->private, &ftrace_filter_fops); > > But this also assumes that ops->private is always a trace_array. Which may > someday change and we will get a hidden bug if it does. > > This is the exact reason I want to look deeper at it. Something like this is more robust: diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index f9d80c7bd9f1..a417ad0f3f24 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4786,24 +4786,48 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, } static int -ftrace_filter_open(struct inode *inode, struct file *file) +__ftrace_regex_open(struct trace_array *tr, int flag, + struct inode *inode, struct file *file) { - struct ftrace_ops *ops = inode->i_private; + struct ftrace_ops *ops; + int ret; + + if (trace_array_get(tr) < 0) + return -ENODEV; + + ret = -EINVAL; + ops = tr->ops; + if (!ops) + goto fail; /* Checks for tracefs lockdown */ - return ftrace_regex_open(ops, - FTRACE_ITER_FILTER | FTRACE_ITER_DO_PROBES, - inode, file); + ret = ftrace_regex_open(ops, flag, inode, file); + if (ret < 0) + goto fail; + + return ret; + fail: + trace_array_put(tr); + return ret; +} + +static int +ftrace_filter_open(struct inode *inode, struct file *file) +{ + struct trace_array *tr = inode->i_private; + + return __ftrace_regex_open(tr, + FTRACE_ITER_FILTER | FTRACE_ITER_DO_PROBES, + inode, file); } static int ftrace_notrace_open(struct inode *inode, struct file *file) { - struct ftrace_ops *ops = inode->i_private; + struct trace_array *tr = inode->i_private; - /* Checks for tracefs lockdown */ - return ftrace_regex_open(ops, FTRACE_ITER_NOTRACE, - inode, file); + return __ftrace_regex_open(tr, FTRACE_ITER_NOTRACE, + inode, file); } /* Type for quick search ftrace basic regexes (globs) from filter_parse_regex */ @@ -7492,15 +7516,15 @@ static const struct file_operations ftrace_graph_notrace_fops = { }; #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ -void ftrace_create_filter_files(struct ftrace_ops *ops, +void ftrace_create_filter_files(struct trace_array *tr, struct dentry *parent) { trace_create_file("set_ftrace_filter", TRACE_MODE_WRITE, parent, - ops, &ftrace_filter_fops); + tr, &ftrace_filter_fops); trace_create_file("set_ftrace_notrace", TRACE_MODE_WRITE, parent, - ops, &ftrace_notrace_fops); + tr, &ftrace_notrace_fops); } /* @@ -7525,6 +7549,7 @@ void ftrace_destroy_filter_files(struct ftrace_ops *ops) static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer) { + struct trace_array *tr; trace_create_file("available_filter_functions", TRACE_MODE_READ, d_tracer, NULL, &ftrace_avail_fops); @@ -7538,7 +7563,9 @@ static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer) trace_create_file("touched_functions", TRACE_MODE_READ, d_tracer, NULL, &ftrace_touched_fops); - ftrace_create_filter_files(&global_ops, d_tracer); + tr = global_ops.private; + if (!WARN_ON(tr == NULL)) + ftrace_create_filter_files(tr, d_tracer); #ifdef CONFIG_FUNCTION_GRAPH_TRACER trace_create_file("set_graph_function", TRACE_MODE_WRITE, d_tracer, diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 74a7a50d1e78..3c111ca88e32 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1340,7 +1340,7 @@ extern void clear_ftrace_function_probes(struct trace_array *tr); int register_ftrace_command(struct ftrace_func_command *cmd); int unregister_ftrace_command(struct ftrace_func_command *cmd); -void ftrace_create_filter_files(struct ftrace_ops *ops, +void ftrace_create_filter_files(struct trace_array *tr, struct dentry *parent); void ftrace_destroy_filter_files(struct ftrace_ops *ops); @@ -1363,11 +1363,12 @@ static inline void clear_ftrace_function_probes(struct trace_array *tr) { } +static inline void ftrace_create_filter_files(struct trace_array *tr, + struct dentry *parent) { } /* * The ops parameter passed in is usually undefined. * This must be a macro. */ -#define ftrace_create_filter_files(ops, parent) do { } while (0) #define ftrace_destroy_filter_files(ops) do { } while (0) #endif /* CONFIG_FUNCTION_TRACER && CONFIG_DYNAMIC_FTRACE */ diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index cd37f2013758..c879d43a5fbb 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -101,7 +101,7 @@ int ftrace_create_function_files(struct trace_array *tr, return ret; } - ftrace_create_filter_files(tr->ops, parent); + ftrace_create_filter_files(tr, parent); return 0; } -- Steve