From cf372342bd064951411ff03c03ab9b241354c48b Mon Sep 17 00:00:00 2001
From: Ksawlii <ksawery.blaszczak@proton.me>
Date: Sun, 24 Nov 2024 00:23:31 +0100
Subject: [PATCH] Revert "ftrace: Fix possible use-after-free issue in
 ftrace_location()"

This reverts commit 2c12c9f7ef34e0ff520387f70736ee71034beac3.
---
 kernel/trace/ftrace.c | 39 ++++++++++++++++-----------------------
 1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 36182e7e0..a781733b2 100755
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1566,15 +1566,12 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end)
 unsigned long ftrace_location_range(unsigned long start, unsigned long end)
 {
 	struct dyn_ftrace *rec;
-	unsigned long ip = 0;
 
-	rcu_read_lock();
 	rec = lookup_rec(start, end);
 	if (rec)
-		ip = rec->ip;
-	rcu_read_unlock();
+		return rec->ip;
 
-	return ip;
+	return 0;
 }
 
 /**
@@ -1587,22 +1584,25 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
  */
 unsigned long ftrace_location(unsigned long ip)
 {
-	unsigned long loc;
+	struct dyn_ftrace *rec;
 	unsigned long offset;
 	unsigned long size;
 
-	loc = ftrace_location_range(ip, ip);
-	if (!loc) {
+	rec = lookup_rec(ip, ip);
+	if (!rec) {
 		if (!kallsyms_lookup_size_offset(ip, &size, &offset))
 			goto out;
 
 		/* map sym+0 to __fentry__ */
 		if (!offset)
-			loc = ftrace_location_range(ip, ip + size - 1);
+			rec = lookup_rec(ip, ip + size - 1);
 	}
 
+	if (rec)
+		return rec->ip;
+
 out:
-	return loc;
+	return 0;
 }
 
 /**
@@ -6331,8 +6331,6 @@ static int ftrace_process_locs(struct module *mod,
 	/* We should have used all pages unless we skipped some */
 	if (pg_unuse) {
 		WARN_ON(!skipped);
-		/* Need to synchronize with ftrace_location_range() */
-		synchronize_rcu();
 		ftrace_free_pages(pg_unuse);
 	}
 	return ret;
@@ -6515,9 +6513,6 @@ void ftrace_release_mod(struct module *mod)
  out_unlock:
 	mutex_unlock(&ftrace_lock);
 
-	/* Need to synchronize with ftrace_location_range() */
-	if (tmp_page)
-		synchronize_rcu();
 	for (pg = tmp_page; pg; pg = tmp_page) {
 
 		/* Needs to be called outside of ftrace_lock */
@@ -6840,7 +6835,6 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
 	unsigned long start = (unsigned long)(start_ptr);
 	unsigned long end = (unsigned long)(end_ptr);
 	struct ftrace_page **last_pg = &ftrace_pages_start;
-	struct ftrace_page *tmp_page = NULL;
 	struct ftrace_page *pg;
 	struct dyn_ftrace *rec;
 	struct dyn_ftrace key;
@@ -6884,8 +6878,12 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
 		ftrace_update_tot_cnt--;
 		if (!pg->index) {
 			*last_pg = pg->next;
-			pg->next = tmp_page;
-			tmp_page = pg;
+			if (pg->records) {
+				free_pages((unsigned long)pg->records, pg->order);
+				ftrace_number_of_pages -= 1 << pg->order;
+			}
+			ftrace_number_of_groups--;
+			kfree(pg);
 			pg = container_of(last_pg, struct ftrace_page, next);
 			if (!(*last_pg))
 				ftrace_pages = pg;
@@ -6902,11 +6900,6 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
 		clear_func_from_hashes(func);
 		kfree(func);
 	}
-	/* Need to synchronize with ftrace_location_range() */
-	if (tmp_page) {
-		synchronize_rcu();
-		ftrace_free_pages(tmp_page);
-	}
 }
 
 void __init ftrace_free_init_mem(void)