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SubjectRe: [PATCH REBASE v4 11/14] mips: Adjust brk randomization offset to fit generic version
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On 7/24/19 7:58 AM, Alexandre Ghiti wrote:
> This commit simply bumps up to 32MB and 1GB the random offset
> of brk, compared to 8MB and 256MB, for 32bit and 64bit respectively.
>
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
> arch/mips/mm/mmap.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
> index a7e84b2e71d7..faa5aa615389 100644
> --- a/arch/mips/mm/mmap.c
> +++ b/arch/mips/mm/mmap.c
> @@ -16,6 +16,7 @@
> #include <linux/random.h>
> #include <linux/sched/signal.h>
> #include <linux/sched/mm.h>
> +#include <linux/sizes.h>
>
> unsigned long shm_align_mask = PAGE_SIZE - 1; /* Sane caches */
> EXPORT_SYMBOL(shm_align_mask);
> @@ -189,11 +190,11 @@ static inline unsigned long brk_rnd(void)
> unsigned long rnd = get_random_long();
>
> rnd = rnd << PAGE_SHIFT;
> - /* 8MB for 32bit, 256MB for 64bit */
> + /* 32MB for 32bit, 1GB for 64bit */
> if (TASK_IS_32BIT_ADDR)
> - rnd = rnd & 0x7ffffful;
> + rnd = rnd & SZ_32M;
> else
> - rnd = rnd & 0xffffffful;
> + rnd = rnd & SZ_1G;
>
> return rnd;
> }

Hi Andrew,

I have just noticed that this patch is wrong, do you want me to send
another version of the entire series or is the following diff enough ?
This mistake gets fixed anyway in patch 13/14 when it gets merged with the
generic version.

Sorry about that,

Thanks,

Alex

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index a7e84b2e71d7..ff6ab87e9c56 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -16,6 +16,7 @@
 #include <linux/random.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/mm.h>
+#include <linux/sizes.h>

 unsigned long shm_align_mask = PAGE_SIZE - 1;  /* Sane caches */
 EXPORT_SYMBOL(shm_align_mask);
@@ -189,11 +190,11 @@ static inline unsigned long brk_rnd(void)
        unsigned long rnd = get_random_long();

        rnd = rnd << PAGE_SHIFT;
-       /* 8MB for 32bit, 256MB for 64bit */
+       /* 32MB for 32bit, 1GB for 64bit */
        if (TASK_IS_32BIT_ADDR)
-               rnd = rnd & 0x7ffffful;
+               rnd = rnd & (SZ_32M - 1);
        else
-               rnd = rnd & 0xffffffful;
+               rnd = rnd & (SZ_1G - 1);

        return rnd;
 }


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