If there is an entry at INT_MAX then idr_for_each_entry() will increment id after handling it. This is undefined behaviour, and is caught by UBSAN. Adding 1U to id forces the operation to be carried out as an unsigned addition which (when assigned to id) will result in INT_MIN. Since there is never an entry stored at INT_MIN, idr_get_next() will return NULL, ending the loop as expected.
Unified · Split
| @@ -185,7 +185,7 @@ static inline void idr_preload_end(void) · 184 unmodified lines | ||
| 185 | 185 | * is convenient for a "not found" value. |
| 186 | 186 | */ |
| 187 | 187 | #define idr_for_each_entry(idr, entry, id) \ |
| 188 | − for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; ++id) | |
| 188 | + for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; id += 1U) | |
| 189 | 189 | |
| 190 | 190 | /** |
| 191 | 191 | * idr_for_each_entry_ul() - Iterate over an IDR's elements of a given type. |