[v6,11/14] mips: Adjust brk randomization offset to fit generic version
diff mbox series

Message ID 20190808061756.19712-12-alex@ghiti.fr
State New
Headers show
Series
  • Provide generic top-down mmap layout functions
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Commit Message

Alex Ghiti Aug. 8, 2019, 6:17 a.m. UTC
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>
Acked-by: Paul Burton <paul.burton@mips.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/mips/mm/mmap.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Comments

Sergei Shtylyov Aug. 8, 2019, 9:19 a.m. UTC | #1
Hello!

On 08.08.2019 9:17, 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>
> Acked-by: Paul Burton <paul.burton@mips.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.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..ff6ab87e9c56 100644
> --- a/arch/mips/mm/mmap.c
> +++ b/arch/mips/mm/mmap.c
[...]
> @@ -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);

    Why not make these 'rnd &= SZ_* - 1', while at it anyways?

[...]

MBR, Sergei
Alex Ghiti Aug. 9, 2019, 9:45 a.m. UTC | #2
On 8/8/19 11:19 AM, Sergei Shtylyov wrote:
> Hello!
>
> On 08.08.2019 9:17, 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>
>> Acked-by: Paul Burton <paul.burton@mips.com>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Reviewed-by: Luis Chamberlain <mcgrof@kernel.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..ff6ab87e9c56 100644
>> --- a/arch/mips/mm/mmap.c
>> +++ b/arch/mips/mm/mmap.c
> [...]
>> @@ -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);
>
>    Why not make these 'rnd &= SZ_* - 1', while at it anyways?


You're right, I could have. Again, this code gets removed afterwards, so 
I think it's ok
to leave it as is.

Anyway, thanks for your remarks Sergei !

Alex


>
> [...]
>
> MBR, Sergei
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Patch
diff mbox series

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;
 }