FAILED: patch "[PATCH] ftrace: Take trace_array reference before accessing its" failed to apply to 6.12-stable tree

PATCH New [email protected] 2 participants 2 messages Sep 8 – Sep 10

Subsystems (3)

Stable branch Tracing ftrace

lore

Share & tools

lore

[email protected]

author maintainer

2026-09-08 13:30 UTC #0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 9100191e5acb2e5ea2313f436667bb5fce129f47
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090804-math-renewal-5eb6@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9100191e5acb2e5ea2313f436667bb5fce129f47 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <[email protected]>
Date: Fri, 28 Aug 2026 22:39:01 -0400
Subject: [PATCH] ftrace: Take trace_array reference before accessing its
ftrace_ops

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 [email protected]

Link https://patch.msgid.link/20260828223901.29e26edb@robin open here

Fixes 591dffdade9f0 ("ftrace: Allow for function tracing instance to filter functions")

Reported-by Breno Leitao <[email protected]>

Tested-by Breno Leitao <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Signed-off-by Steven Rostedt <[email protected]>

include/linux/ftrace.h +3 -2

index 02bc5027523a..bd76a16a63af 100644
@@ -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; })

kernel/trace/ftrace.c +37 ~~-20~~

120 lines not on this page · raw message

kernel/trace/trace.h +3 -2

index 74a7a50d1e78..3c111ca88e32 100644
@@ -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 */

kernel/trace/trace_functions.c +1 -1

index cd37f2013758..c879d43a5fbb 100644
@@ -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;
 }

kernel/trace/trace_stack.c +1 -1

index 0aa2514a6593..e7f4e523587d 100644
@@ -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);
 }

Sasha Levin

maintainer

2026-09-10 14:03 UTC #1 lore raw

PATCH 1/1 ftrace: Take trace_array reference before accessing its ftrace_ops

From: Steven Rostedt <[email protected]>

[ Upstream commit 9100191e5acb2e5ea2313f436667bb5fce129f47 ]