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authorDaniel Cashman <dcashman@android.com>2016-02-26 15:19:34 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-02-27 10:28:52 -0800
commitec9ee4acd97c0039a61c0ae4f12705767ae62153 (patch)
tree8f86b8fda1f9fd178643f42299f3e6f91cab31e3 /drivers/char
parent8479eba7781fa9ffb28268840de6facfc12c35a7 (diff)
drivers: char: random: add get_random_long()
Commit d07e22597d1d ("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. This patch (of 2): Add get_random_long(). Signed-off-by: Daniel Cashman <dcashman@android.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: David S. Miller <davem@davemloft.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Nick Kralevich <nnk@google.com> Cc: Jeff Vander Stoep <jeffv@google.com> Cc: Mark Salyzyn <salyzyn@android.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/random.c22
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> .....]