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From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 1/4] powerpc/64s: implement probe_kernel_read/write without touching AMR
Date: Fri, 27 Mar 2020 08:13:56 +0100
Message-ID: <d619b378-3a88-f941-b2d5-42b79574e2ab@c-s.fr> (raw)
In-Reply-To: <20200327070240.427074-1-npiggin@gmail.com>



Le 27/03/2020 à 08:02, Nicholas Piggin a écrit :
> There is no need to allow user accesses when probing kernel addresses.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   arch/powerpc/include/asm/uaccess.h | 25 ++++++++++-----
>   arch/powerpc/lib/Makefile          |  2 +-
>   arch/powerpc/lib/uaccess.c         | 50 ++++++++++++++++++++++++++++++
>   3 files changed, 68 insertions(+), 9 deletions(-)
>   create mode 100644 arch/powerpc/lib/uaccess.c
> 

[...]

> diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> index b8de3be10eb4..a15060b5008e 100644
> --- a/arch/powerpc/lib/Makefile
> +++ b/arch/powerpc/lib/Makefile
> @@ -36,7 +36,7 @@ extra-$(CONFIG_PPC64)	+= crtsavres.o
>   endif
>   
>   obj-$(CONFIG_PPC_BOOK3S_64) += copyuser_power7.o copypage_power7.o \
> -			       memcpy_power7.o
> +			       memcpy_power7.o uaccess.o

Why only book3s/64 ? It applies to the 8xx and book3s/32 as well, I 
think it should just be for all powerpc.

>   
>   obj64-y	+= copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
>   	   memcpy_64.o memcpy_mcsafe_64.o
> diff --git a/arch/powerpc/lib/uaccess.c b/arch/powerpc/lib/uaccess.c
> new file mode 100644
> index 000000000000..0057ab52d6fe
> --- /dev/null
> +++ b/arch/powerpc/lib/uaccess.c
> @@ -0,0 +1,50 @@
> +#include <linux/mm.h>
> +#include <linux/uaccess.h>
> +
> +static __always_inline long
> +probe_read_common(void *dst, const void __user *src, size_t size)
> +{
> +	long ret;
> +
> +	pagefault_disable();
> +	ret = raw_copy_from_user_allowed(dst, src, size);
> +	pagefault_enable();
> +
> +	return ret ? -EFAULT : 0;
> +}
> +
> +static __always_inline long
> +probe_write_common(void __user *dst, const void *src, size_t size)
> +{
> +	long ret;
> +
> +	pagefault_disable();
> +	ret = raw_copy_to_user_allowed(dst, src, size);
> +	pagefault_enable();
> +
> +	return ret ? -EFAULT : 0;
> +}
> +
> +long probe_kernel_read(void *dst, const void *src, size_t size)
> +{
> +	long ret;
> +	mm_segment_t old_fs = get_fs();
> +
> +	set_fs(KERNEL_DS);
> +	ret = probe_read_common(dst, (__force const void __user *)src, size);

I think you should squash probe_read_common() here, having it separated 
is a lot of lines for no added value. It also may make people believe it 
overwrites the generic probe_read_common()


> +	set_fs(old_fs);
> +
> +	return ret;
> +}
> +
> +long probe_kernel_write(void *dst, const void *src, size_t size)
> +{
> +	long ret;
> +	mm_segment_t old_fs = get_fs();
> +
> +	set_fs(KERNEL_DS);
> +	ret = probe_write_common((__force void __user *)dst, src, size);

Same comment as for probe_read_common()

> +	set_fs(old_fs);
> +
> +	return ret;
> +}
> 

Christophe

      parent reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-27  7:02 Nicholas Piggin
2020-03-27  7:02 ` [PATCH 2/4] powerpc/64s: use mmu_has_feature in set_kuap() and get_kuap() Nicholas Piggin
2020-03-27  7:02 ` [PATCH 3/4] powerpc/uaccess: evaluate macro arguments once, before user access is allowed Nicholas Piggin
2020-03-27  7:21   ` Christophe Leroy
2020-03-27  7:02 ` [PATCH 4/4] powerpc/uaccess: add more __builtin_expect annotations Nicholas Piggin
2020-03-27  7:13 ` Christophe Leroy [this message]

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