On 01/12/15 20:10, Daniel Cashman wrote:
> From: dcashman <dcashman@xxxxxxxxxx>
>
> arm64: arch_mmap_rnd() uses STACK_RND_MASK to generate the
> random offset for the mmap base address. This value represents a
> compromise between increased ASLR effectiveness and avoiding
> address-space fragmentation. Replace it with a Kconfig option, which
> is sensibly bounded, so that platform developers may choose where to
> place this compromise. Keep default values as new minimums.
>
> Signed-off-by: Daniel Cashman <dcashman@xxxxxxxxxxx>
> ---
> arch/arm64/Kconfig | 31 +++++++++++++++++++++++++++++++
> arch/arm64/mm/mmap.c | 8 ++++++--
> 2 files changed, 37 insertions(+), 2 deletions(-)
[snip]
> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
> index ed17747..af461b9 100644
> --- a/arch/arm64/mm/mmap.c
> +++ b/arch/arm64/mm/mmap.c
> @@ -51,8 +51,12 @@ unsigned long arch_mmap_rnd(void)
> {
> unsigned long rnd;
>
> - rnd = (unsigned long)get_random_int() & STACK_RND_MASK;
> -
> +ifdef CONFIG_COMPAT
> + if (test_thread_flag(TIF_32BIT))
> + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_compat_bits);
> + else
> +#endif
> + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits);
> return rnd << PAGE_SHIFT;
> }
The above is causing a build failure on -next today.
commit 42a6c8953112a9856dd09148c3d6a2cc106b6003
Author: Jon Hunter <jonathanh@xxxxxxxxxx>
Date: Mon Dec 7 10:15:47 2015 +0000
ARM64: mm: Fix build failure caused by invalid ifdef statement
Commit 2e4614190421 ("arm64-mm-support-arch_mmap_rnd_bits-v4") caused the
following build failure due to a missing "#". Fix this.
arch/arm64/mm/mmap.c: In function ‘arch_mmap_rnd’:
arch/arm64/mm/mmap.c:54:1: error: ‘ifdef’ undeclared (first use in this function)
ifdef CONFIG_COMPAT
^
Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index af461b935137..e59a75a308bc 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -51,7 +51,7 @@ unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;
-ifdef CONFIG_COMPAT
+#ifdef CONFIG_COMPAT
if (test_thread_flag(TIF_32BIT))
rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_compat_bits);
else
Cheers
Jon
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