[bug report] user_events: Add minimal support for trace_event into ftrace

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Beau Belgrave,

The patch 7f5a08c79df3: "user_events: Add minimal support for
trace_event into ftrace" from Jan 18, 2022, leads to the following
Smatch static checker warning:

	kernel/trace/trace_events_user.c:399 user_event_parse_field()
	error: uninitialized symbol 'name'.

kernel/trace/trace_events_user.c
    314 static int user_event_parse_field(char *field, struct user_event *user,
    315                                   u32 *offset)
    316 {
    317         char *part, *type, *name;
    318         u32 depth = 0, saved_offset = *offset;
    319         int len, size = -EINVAL;
    320         bool is_struct = false;
    321 
    322         field = skip_spaces(field);
    323 
    324         if (*field == '\0')
    325                 return 0;
    326 
    327         /* Handle types that have a space within */
    328         len = str_has_prefix(field, "unsigned ");
    329         if (len)
    330                 goto skip_next;
    331 
    332         len = str_has_prefix(field, "struct ");
    333         if (len) {
    334                 is_struct = true;
    335                 goto skip_next;
    336         }
    337 
    338         len = str_has_prefix(field, "__data_loc unsigned ");
    339         if (len)
    340                 goto skip_next;
    341 
    342         len = str_has_prefix(field, "__data_loc ");
    343         if (len)
    344                 goto skip_next;
    345 
    346         len = str_has_prefix(field, "__rel_loc unsigned ");
    347         if (len)
    348                 goto skip_next;
    349 
    350         len = str_has_prefix(field, "__rel_loc ");
    351         if (len)
    352                 goto skip_next;
    353 
    354         goto parse;
    355 skip_next:
    356         type = field;
    357         field = strpbrk(field + len, " ");
    358 
    359         if (field == NULL)
    360                 return -EINVAL;
    361 
    362         *field++ = '\0';
    363         depth++;
    364 parse:
    365         while ((part = strsep(&field, " ")) != NULL) {
    366                 switch (depth++) {
    367                 case FIELD_DEPTH_TYPE:
    368                         type = part;
    369                         break;
    370                 case FIELD_DEPTH_NAME:
    371                         name = part;
                                ^^^^^^^^^^^
name is only initialized here.  Otherwise uninitialized.

    372                         break;
    373                 case FIELD_DEPTH_SIZE:
    374                         if (!is_struct)
    375                                 return -EINVAL;
    376 
    377                         if (kstrtou32(part, 10, &size))
    378                                 return -EINVAL;
    379                         break;
    380                 default:
    381                         return -EINVAL;
    382                 }
    383         }
    384 
    385         if (depth < FIELD_DEPTH_SIZE)
    386                 return -EINVAL;
    387 
    388         if (depth == FIELD_DEPTH_SIZE)
    389                 size = user_field_size(type);
    390 
    391         if (size == 0)
    392                 return -EINVAL;
    393 
    394         if (size < 0)
    395                 return size;
    396 
    397         *offset = saved_offset + size;
    398 
--> 399         return user_event_add_field(user, type, name, saved_offset, size,
    400                                     type[0] != 'u', FILTER_OTHER);
    401 }

regards,
dan carpenter