diff options
| -rw-r--r-- | kernel/sysctl_binary.c | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c index 112533d..8f5d16e 100644 --- a/kernel/sysctl_binary.c +++ b/kernel/sysctl_binary.c @@ -1417,6 +1417,35 @@ static void deprecated_sysctl_warning(const int *name, int nlen) return; } +#define WARN_ONCE_HASH_BITS 8 +#define WARN_ONCE_HASH_SIZE (1<<WARN_ONCE_HASH_BITS) + +static DECLARE_BITMAP(warn_once_bitmap, WARN_ONCE_HASH_SIZE); + +#define FNV32_OFFSET 2166136261U +#define FNV32_PRIME 0x01000193 + +/* + * Print each legacy sysctl (approximately) only once. + * To avoid making the tables non-const use a external + * hash-table instead. + * Worst case hash collision: 6, but very rarely. + * NOTE! We don't use the SMP-safe bit tests. We simply + * don't care enough. + */ +static void warn_on_bintable(const int *name, int nlen) +{ + int i; + u32 hash = FNV32_OFFSET; + + for (i = 0; i < nlen; i++) + hash = (hash ^ name[i]) * FNV32_PRIME; + hash %= WARN_ONCE_HASH_SIZE; + if (__test_and_set_bit(hash, warn_once_bitmap)) + return; + deprecated_sysctl_warning(name, nlen); +} + static ssize_t do_sysctl(int __user *args_name, int nlen, void __user *oldval, size_t oldlen, void __user *newval, size_t newlen) { @@ -1431,7 +1460,7 @@ static ssize_t do_sysctl(int __user *args_name, int nlen, if (get_user(name[i], args_name + i)) return -EFAULT; - deprecated_sysctl_warning(name, nlen); + warn_on_bintable(name, nlen); return binary_sysctl(name, nlen, oldval, oldlen, newval, newlen); } |
