diff options
Diffstat (limited to 'include/linux/cpumask.h')
| -rw-r--r-- | include/linux/cpumask.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index fe29ac7cc469..4592d0845941 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -1071,4 +1071,22 @@ cpumap_print_list_to_buf(char *buf, const struct cpumask *mask, [0] = 1UL \ } } +/* + * Provide a valid theoretical max size for cpumap and cpulist sysfs files + * to avoid breaking userspace which may allocate a buffer based on the size + * reported by e.g. fstat. + * + * for cpumap NR_CPUS * 9/32 - 1 should be an exact length. + * + * For cpulist 7 is (ceil(log10(NR_CPUS)) + 1) allowing for NR_CPUS to be up + * to 2 orders of magnitude larger than 8192. And then we divide by 2 to + * cover a worst-case of every other cpu being on one of two nodes for a + * very large NR_CPUS. + * + * Use PAGE_SIZE as a minimum for smaller configurations. + */ +#define CPUMAP_FILE_MAX_BYTES ((((NR_CPUS * 9)/32 - 1) > PAGE_SIZE) \ + ? (NR_CPUS * 9)/32 - 1 : PAGE_SIZE) +#define CPULIST_FILE_MAX_BYTES (((NR_CPUS * 7)/2 > PAGE_SIZE) ? (NR_CPUS * 7)/2 : PAGE_SIZE) + #endif /* __LINUX_CPUMASK_H */ |