register_ftrace_function_probe() returns the number of functions it registered, which can be zero, it can also return a negative number if something went wrong. But event_enable_func() only checks for the case that it didn't register anything, it needs to also check for the case that something went wrong and return that error code as well. Added some comments about the code as well, to make it more understandable.
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| @@ -2061,11 +2061,18 @@ event_enable_func(struct ftrace_hash *hash, · 2060 unmodified lines | ||
| 2061 | 2061 | if (ret < 0) |
| 2062 | 2062 | goto out_put; |
| 2063 | 2063 | ret = register_ftrace_function_probe(glob, ops, data); |
| 2064 | + /* | |
| 2065 | + * The above returns on success the # of functions enabled, | |
| 2066 | + * but if it didn't find any functions it returns zero. | |
| 2067 | + * Consider no functions a failure too. | |
| 2068 | + */ | |
| 2064 | 2069 | if (!ret) { |
| 2065 | 2070 | ret = -ENOENT; |
| 2066 | 2071 | goto out_disable; |
| 2067 | − } else | |
| 2068 | − ret = 0; | |
| 2072 | + } else if (ret < 0) | |
| 2073 | + goto out_disable; | |
| 2074 | + /* Just return zero, not the number of enabled functions */ | |
| 2075 | + ret = 0; | |
| 2069 | 2076 | out: |
| 2070 | 2077 | mutex_unlock(&event_mutex); |
| 2071 | 2078 | return ret; |