From: Alexei Starovoitov <ast@xxxxxxxxxx>
[ Upstream commit 8a141dd7f7060d1e64c14a5257e0babae20ac99b ]
The following sequence of commands:
register_ftrace_direct(ip, addr1);
modify_ftrace_direct(ip, addr1, addr2);
unregister_ftrace_direct(ip, addr2);
will cause the kernel to warn:
[ 30.179191] WARNING: CPU: 2 PID: 1961 at kernel/trace/ftrace.c:5223 unregister_ftrace_direct+0x130/0x150
[ 30.180556] CPU: 2 PID: 1961 Comm: test_progs W O 5.12.0-rc2-00378-g86bc10a0a711-dirty #3246
[ 30.182453] RIP: 0010:unregister_ftrace_direct+0x130/0x150
When modify_ftrace_direct() changes the addr from old to new it should update
the addr stored in ftrace_direct_funcs. Otherwise the final
unregister_ftrace_direct() won't find the address and will cause the splat.
Fixes: 0567d6809182 ("ftrace: Add modify_ftrace_direct()")
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20210316195815.34714-1-alexei.starovoitov@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/trace/ftrace.c | 43 ++++++++++++++++++++++++++++++++++++++-----
1 file changed, 38 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 9c1bba8cc51b..82041bbf8fc2 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5045,6 +5045,20 @@ struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr)
return NULL;
}
+static struct ftrace_direct_func *ftrace_alloc_direct_func(unsigned long addr)
+{
+ struct ftrace_direct_func *direct;
+
+ direct = kmalloc(sizeof(*direct), GFP_KERNEL);
+ if (!direct)
+ return NULL;
+ direct->addr = addr;
+ direct->count = 0;
+ list_add_rcu(&direct->next, &ftrace_direct_funcs);
+ ftrace_direct_func_count++;
+ return direct;
+}
+
/**
* register_ftrace_direct - Call a custom trampoline directly
* @ip: The address of the nop at the beginning of a function
@@ -5120,15 +5134,11 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
direct = ftrace_find_direct_func(addr);
if (!direct) {
- direct = kmalloc(sizeof(*direct), GFP_KERNEL);
+ direct = ftrace_alloc_direct_func(addr);
if (!direct) {
kfree(entry);
goto out_unlock;
}
- direct->addr = addr;
- direct->count = 0;
- list_add_rcu(&direct->next, &ftrace_direct_funcs);
- ftrace_direct_func_count++;
}
entry->ip = ip;
@@ -5329,6 +5339,7 @@ int __weak ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
int modify_ftrace_direct(unsigned long ip,
unsigned long old_addr, unsigned long new_addr)
{
+ struct ftrace_direct_func *direct, *new_direct = NULL;
struct ftrace_func_entry *entry;
struct dyn_ftrace *rec;
int ret = -ENODEV;
@@ -5344,6 +5355,20 @@ int modify_ftrace_direct(unsigned long ip,
if (entry->direct != old_addr)
goto out_unlock;
+ direct = ftrace_find_direct_func(old_addr);
+ if (WARN_ON(!direct))
+ goto out_unlock;
+ if (direct->count > 1) {
+ ret = -ENOMEM;
+ new_direct = ftrace_alloc_direct_func(new_addr);
+ if (!new_direct)
+ goto out_unlock;
+ direct->count--;
+ new_direct->count++;
+ } else {
+ direct->addr = new_addr;
+ }
+
/*
* If there's no other ftrace callback on the rec->ip location,
* then it can be changed directly by the architecture.
@@ -5357,6 +5382,14 @@ int modify_ftrace_direct(unsigned long ip,
ret = 0;
}
+ if (unlikely(ret && new_direct)) {
+ direct->count++;
+ list_del_rcu(&new_direct->next);
+ synchronize_rcu_tasks();
+ kfree(new_direct);
+ ftrace_direct_func_count--;
+ }
+
out_unlock:
mutex_unlock(&ftrace_lock);
mutex_unlock(&direct_mutex);
--
2.30.1
