diff options
| author | dcashman <dcashman@google.com> | 2016-02-24 13:27:06 -0800 |
|---|---|---|
| committer | Amit Pundir <amit.pundir@linaro.org> | 2016-04-07 16:49:59 +0530 |
| commit | 06bfe14bdda83b9544c6b7bd4cdf738013e51ae8 (patch) | |
| tree | 52910af5f26f4d4498c4eee1021506ce593f1c59 /drivers/char | |
| parent | 772d83a92971662b11316a2a266730d18c1bdeda (diff) | |
FROMLIST: drivers: char: random: add get_random_long()
(cherry picked from commit https://lkml.org/lkml/2016/2/4/831)
d07e22597d1d355 ("mm: mmap: add new /proc tunable for mmap_base ASLR")
added the ability to choose from a range of values to use for entropy
count in generating the random offset to the mmap_base address. The
maximum value on this range was set to 32 bits for 64-bit x86 systems, but
this value could be increased further, requiring more than the 32 bits of
randomness provided by get_random_int(), as is already possible for arm64.
Add a new function: get_random_long() which more naturally fits with the
mmap usage of get_random_int() but operates exactly the same as
get_random_int().
Also, fix the shifting constant in mmap_rnd() to be an unsigned long so
that values greater than 31 bits generate an appropriate mask without
overflow. This is especially important on x86, as its shift instruction
uses a 5-bit mask for the shift operand, which meant that any value for
mmap_rnd_bits over 31 acts as a no-op and effectively disables mmap_base
randomization.
Finally, replace calls to get_random_int() with get_random_long() where
appropriate.
Bug: 26963541
Signed-off-by: Daniel Cashman <dcashman@android.com>
Signed-off-by: Daniel Cashman <dcashman@google.com>
Change-Id: I5b45621088666d5d1dfbf43952f25ea0798b10ba
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/random.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index d0da5d852d41..b583e5336630 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1819,6 +1819,28 @@ unsigned int get_random_int(void) EXPORT_SYMBOL(get_random_int); /* + * Same as get_random_int(), but returns unsigned long. + */ +unsigned long get_random_long(void) +{ + __u32 *hash; + unsigned long ret; + + if (arch_get_random_long(&ret)) + return ret; + + hash = get_cpu_var(get_random_int_hash); + + hash[0] += current->pid + jiffies + random_get_entropy(); + md5_transform(hash, random_int_secret); + ret = *(unsigned long *)hash; + put_cpu_var(get_random_int_hash); + + return ret; +} +EXPORT_SYMBOL(get_random_long); + +/* * randomize_range() returns a start address such that * * [...... <range> .....] |