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ftrace: Fix modify_ftrace_direct. 

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: 0567d68091 ("ftrace: Add modify_ftrace_direct()")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lore.kernel.org/bpf/20210316195815.34714-1-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2021-03-16 12:58:15 -07:00 committed by Daniel Borkmann
parent 31254dc956
commit 8a141dd7f7
1 changed files with 38 additions and 5 deletions
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43
kernel/trace/ftrace.c
View File

@ -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);