From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) (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 3679E27A47F; Fri, 28 Aug 2026 19:59:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787947144; cv=none; b=fc4Ob4RFSLh10BIKhNPTn7Zij51FOM1TtafTcTWYqybazp78uQTgbq4ngjMuMJfS1GVfeKCmeWjZu/CoqUpjJW9Zqg4D5CdkbHvN/gQtATIpR0xgq4qWjnn2v5s/3WeAk1Ry4PQfRXVgECHnVDRJrzw3YaEqFjD3X9uznXBIqMQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787947144; c=relaxed/simple; bh=LgMOatiy+7XEyiCvqb4M1kKcLipTyx0ODtzakxJIjiA=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=RkV1oyWWUDC+olcr+jKgKSzMG4mWtGDyrS1fBLYEOY2y5mhY5r5O1im44DM4eI87kw/j9m/Fd48o+rjhsX61W5E3rvYz2uUhxryqDQ3BbZx+6ZAhKzExXux4VWX8APLu3p9+yUpJPllocWGi5+dG/M5mTztoBXmSLUCe1b1b4Ic= 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=5tzIGdy2; arc=none smtp.client-ip=216.40.44.12 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="5tzIGdy2" Received: from omf04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 5BC7CA056A; Fri, 28 Aug 2026 19:58:54 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf04.hostedemail.com (Postfix) with ESMTPA id 8DFE72002B; Fri, 28 Aug 2026 19:58:52 +0000 (UTC) Date: Fri, 28 Aug 2026 15:59:42 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , Mark Rutland , Breno Leitao Subject: [PATCH] ftrace: Take trace_array reference before accessing its ftrace_ops Message-ID: <20260828155942.445f46e5@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-Rspamd-Server: rspamout05 X-Rspamd-Queue-Id: 8DFE72002B X-Stat-Signature: 1w18up9pq5e83gw6exubumdrwzsuiahp X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18Yb9jRXkSyPDoXLbuSUOgC5KL9Ug1cS/k= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=goodmis.org; h=date:from:to:cc:subject:message-id:mime-version:content-type:content-transfer-encoding; s=dkim1; bh=1/oOOJl68blsipXdwWwm/N25KYqVOSFFcMXMMZnjr0g=; b=5tzIGdy285KOFGiOi29CMVK7EAiyxxk8cJFNRJjO2KQ0NjPYzHI7smRHe/u6dkLMFL+6LGdJUVoHc6l+hGqEzwDBm4D2Vytxalx7EI52yt92jq4Wpyr2zQSNxbHNt8DiByRyA1Rocl64JD/tssh7ojctiUIeaJW7kbwaLjxLFEU= X-HE-Tag: 1787947132-504366 X-HE-Meta: U2FsdGVkX1/CQrSRG4dsWZo4R5CUyOZdH6yYH/GpYuGXqQBu22yyyb7pzXRgNs3D4jxqi/lm9ToPzzuoL3jayETzSkTqsNHVBb6u64DwF4Zgjo4Rq+28aAO9kAuHQDT2Vake3tNtxy4MgHEmOsHk3MeOnQZ2PJ3i6uI+3vxxVZ6KE+JhB8lGjYcsV5BbbNH0izXN00xfkc8Y00It5aAQylTALEqUdqaGfXJ9xmLFFd/K2E7J7vxL/fQLOedntq9+cFBqShSLbr1Z8p5+MiQnCbms9yX3TVCSTo/8prYubLuQwhW6H4kvOb8J5nITN1Is9mL524E15yhzfbyDtQXLyQgPgpJsZsc0Wgs2wyoY/H08geuVvwqFyU2M9ImV5gRCKDa7PlnwJXG2l/2a/GdZhENYb92kdl3RKnPt3Di4QGCZdCbvaOaMpW471KD36gTeOavCj1rtFl8= From: Steven Rostedt The trace instance files set_ftrace_filter and set_ftrace_notrace was updated to work with specific trace instances (trace_arrays). The issue is that when these files are opened, there is a small race window where it will use the ftrace_ops from the inode->private pointer to get a reference to the trace_array and then take its reference. The problem is that the ftrace_ops itself could be freed. If the rmdir on the instance happens at the same time the set_ftrace_filter file is opened, the rmdir could have also freed the ftrace_ops and referencing it will cause a use-after-free bug and crash the kernel. Instead, pass in the trace_array as the file private data (NULL for the top level instance), and then pass both the trace_array and the ftrace_ops to the ftrace_regex_open() function. If the trace_array is NULL, then it just uses the ftrace_ops without the need to take its reference (like normal). If the ftrace_ops is NULL, that is only the case for the top level instance and the global_ops can be used. This allows the trace_array to have its reference incremented before touching the ftrace_ops that could also be freed when the instance is. Cc: stable@vger.kernel.org Fixes: 591dffdade9f0 ("ftrace: Allow for function tracing instance to filter functions") Reported-by: Breno Leitao Closes: https://lore.kernel.org/all/apGORjltZgAiAYHT@gmail.com/ Signed-off-by: Steven Rostedt --- include/linux/ftrace.h | 5 ++-- kernel/trace/ftrace.c | 52 ++++++++++++++++++++-------------- kernel/trace/trace.h | 5 ++-- kernel/trace/trace_functions.c | 2 +- kernel/trace/trace_stack.c | 2 +- 5 files changed, 39 insertions(+), 27 deletions(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 02bc5027523a..bd76a16a63af 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -866,8 +866,9 @@ unsigned long ftrace_get_addr_new(struct dyn_ftrace *rec); unsigned long ftrace_get_addr_curr(struct dyn_ftrace *rec); extern ftrace_func_t ftrace_trace_function; +struct trace_array; -int ftrace_regex_open(struct ftrace_ops *ops, int flag, +int ftrace_regex_open(struct trace_array *tr, struct ftrace_ops *ops, int flag, struct inode *inode, struct file *file); ssize_t ftrace_filter_write(struct file *file, const char __user *ubuf, size_t cnt, loff_t *ppos); @@ -1077,7 +1078,7 @@ static inline unsigned long ftrace_location(unsigned long ip) * have them defined when ftrace is not enabled, but these * functions may still be called. Use a macro instead of inline. */ -#define ftrace_regex_open(ops, flag, inod, file) ({ -ENODEV; }) +#define ftrace_regex_open(tr, ops, flag, inode, file) ({ -ENODEV; }) #define ftrace_set_early_filter(ops, buf, enable) do { } while (0) #define ftrace_set_filter_ip(ops, ip, remove, reset) ({ -ENODEV; }) #define ftrace_set_filter_ips(ops, ips, cnt, remove, reset) ({ -ENODEV; }) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index f9d80c7bd9f1..4babd86c7be0 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4677,7 +4677,8 @@ ftrace_avail_addrs_open(struct inode *inode, struct file *file) /** * ftrace_regex_open - initialize function tracer filter files - * @ops: The ftrace_ops that hold the hash filters + * @tr: The trace_array that holds the ftrace_ops [optional] + * @ops: The ftrace_ops that hold the hash filters [optional] * @flag: The type of filter to process * @inode: The inode, usually passed in to your open routine * @file: The file, usually passed in to your open routine @@ -4691,26 +4692,38 @@ ftrace_avail_addrs_open(struct inode *inode, struct file *file) * tracing_lseek() should be used as the lseek routine, and * release must call ftrace_regex_release(). * + * Note, If @tr is not NULL, its reference has to be taken before + * @ops may be referenced. + * If @ops is NULL and @tr is not, then @tr->ops is used. + * If both @tr and @ops are NULL, then the &global_ops is + * to be used. + * * Returns: 0 on success or a negative errno value on failure */ int -ftrace_regex_open(struct ftrace_ops *ops, int flag, +ftrace_regex_open(struct trace_array *tr, struct ftrace_ops *ops, int flag, struct inode *inode, struct file *file) { - struct ftrace_iterator *iter; + struct ftrace_iterator *iter = NULL; struct ftrace_hash *hash; struct list_head *mod_head; - struct trace_array *tr = ops->private; - int ret = -ENOMEM; - - ftrace_ops_init(ops); + int ret = -ENODEV; if (unlikely(ftrace_disabled)) return -ENODEV; - if (tracing_check_open_get_tr(tr)) + if (tr && tracing_check_open_get_tr(tr)) return -ENODEV; + if (!ops) + ops = tr ? tr->ops : &global_ops; + + if (WARN_ON_ONCE(!ops)) + goto out; + + ftrace_ops_init(ops); + + ret = -ENOMEM; iter = kzalloc_obj(*iter); if (!iter) goto out; @@ -4788,21 +4801,19 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, static int ftrace_filter_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_FILTER | FTRACE_ITER_DO_PROBES, - inode, file); + return ftrace_regex_open(tr, NULL, + 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, + return ftrace_regex_open(tr, NULL, FTRACE_ITER_NOTRACE, inode, file); } @@ -7492,15 +7503,15 @@ 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); } /* @@ -7525,7 +7536,6 @@ void ftrace_destroy_filter_files(struct ftrace_ops *ops) static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer) { - trace_create_file("available_filter_functions", TRACE_MODE_READ, d_tracer, NULL, &ftrace_avail_fops); @@ -7538,7 +7548,7 @@ 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); + ftrace_create_filter_files(NULL, 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; } diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index 0aa2514a6593..e7f4e523587d 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -499,7 +499,7 @@ stack_trace_filter_open(struct inode *inode, struct file *file) struct ftrace_ops *ops = inode->i_private; /* Checks for tracefs lockdown */ - return ftrace_regex_open(ops, FTRACE_ITER_FILTER, + return ftrace_regex_open(NULL, ops, FTRACE_ITER_FILTER, inode, file); } -- 2.53.0