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From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Christoph Hellwig <hch@lst.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Michael Ellerman <mpe@ellerman.id.au>,
x86@kernel.org, linux-arch@vger.kernel.org,
Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org,
Luis Chamberlain <mcgrof@kernel.org>,
linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Alexey Dobriyan <adobriyan@gmail.com>
Subject: Re: [PATCH 14/14] powerpc: remove address space overrides using set_fs()
Date: Thu, 3 Sep 2020 18:03:56 +0200 [thread overview]
Message-ID: <7b895389-3da8-f634-4a13-82e533398ec5@csgroup.eu> (raw)
In-Reply-To: <20200903155644.GA23521@lst.de>
Le 03/09/2020 à 17:56, Christoph Hellwig a écrit :
> On Thu, Sep 03, 2020 at 05:49:09PM +0200, Christoph Hellwig wrote:
>> On Thu, Sep 03, 2020 at 05:43:25PM +0200, Christophe Leroy wrote:
>>>
>>>
>>> Le 03/09/2020 à 16:22, Christoph Hellwig a écrit :
>>>> Stop providing the possibility to override the address space using
>>>> set_fs() now that there is no need for that any more.
>>>>
>>>> Signed-off-by: Christoph Hellwig <hch@lst.de>
>>>> ---
>>>
>>>
>>>> -static inline int __access_ok(unsigned long addr, unsigned long size,
>>>> - mm_segment_t seg)
>>>> +static inline bool __access_ok(unsigned long addr, unsigned long size)
>>>> {
>>>> - if (addr > seg.seg)
>>>> - return 0;
>>>> - return (size == 0 || size - 1 <= seg.seg - addr);
>>>> + if (addr >= TASK_SIZE_MAX)
>>>> + return false;
>>>> + return size == 0 || size <= TASK_SIZE_MAX - addr;
>>>> }
>>>
>>> You don't need to test size == 0 anymore. It used to be necessary because
>>> of the 'size - 1', as size is unsigned.
>>>
>>> Now you can directly do
>>>
>>> return size <= TASK_SIZE_MAX - addr;
>>>
>>> If size is 0, this will always be true (because you already know that addr
>>> is not >= TASK_SIZE_MAX
>>
>> True. What do you think of Linus' comment about always using the
>> ppc32 version on ppc64 as well with this?
I have nothing against it. That's only adding a substract, all args are
already in registers so that will be in the noise for a modern CPU.
>
> i.e. something like this folded in:
>
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 5363f7fc6dd06c..be070254e50943 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -11,26 +11,14 @@
> #ifdef __powerpc64__
> /* We use TASK_SIZE_USER64 as TASK_SIZE is not constant */
> #define TASK_SIZE_MAX TASK_SIZE_USER64
> -
> -/*
> - * This check is sufficient because there is a large enough gap between user
> - * addresses and the kernel addresses.
> - */
> -static inline bool __access_ok(unsigned long addr, unsigned long size)
> -{
> - return addr < TASK_SIZE_MAX && size < TASK_SIZE_MAX;
> -}
> -
> #else
> #define TASK_SIZE_MAX TASK_SIZE
> +#endif
>
> static inline bool __access_ok(unsigned long addr, unsigned long size)
> {
> - if (addr >= TASK_SIZE_MAX)
> - return false;
> - return size == 0 || size <= TASK_SIZE_MAX - addr;
> + return addr < TASK_SIZE_MAX && size <= TASK_SIZE_MAX - addr;
> }
> -#endif /* __powerpc64__ */
>
> #define access_ok(addr, size) \
> (__chk_user_ptr(addr), \
>
Christophe
next prev parent reply other threads:[~2020-09-03 16:08 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 14:22 remove the last set_fs() in common code, and remove it for x86 and powerpc v3 Christoph Hellwig
2020-09-03 14:22 ` [PATCH 01/14] proc: remove a level of indentation in proc_get_inode Christoph Hellwig
2020-09-03 14:22 ` [PATCH 02/14] proc: cleanup the compat vs no compat file ops Christoph Hellwig
2020-09-03 14:22 ` [PATCH 03/14] proc: add a read_iter method to proc proc_ops Christoph Hellwig
2020-09-03 14:22 ` [PATCH 04/14] sysctl: Convert to iter interfaces Christoph Hellwig
2020-09-03 14:22 ` [PATCH 05/14] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-10-01 22:38 ` Eric Biggers
2020-10-01 22:40 ` Al Viro
2020-10-02 16:27 ` Linus Torvalds
2020-10-09 22:06 ` Eric Biggers
2020-10-10 1:03 ` Linus Torvalds
2020-10-10 1:19 ` Eric Biggers
2020-10-10 1:29 ` Linus Torvalds
2020-10-10 1:55 ` Alexander Viro
2020-10-14 5:51 ` Christoph Hellwig
2020-09-03 14:22 ` [PATCH 06/14] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-09-03 14:22 ` [PATCH 07/14] uaccess: add infrastructure for kernel builds with set_fs() Christoph Hellwig
2020-09-03 14:22 ` [PATCH 08/14] test_bitmap: remove user bitmap tests Christoph Hellwig
2020-09-03 14:22 ` [PATCH 09/14] lkdtm: remove set_fs-based tests Christoph Hellwig
2020-09-03 14:22 ` [PATCH 10/14] x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h Christoph Hellwig
2020-09-03 14:22 ` [PATCH 11/14] x86: make TASK_SIZE_MAX usable from assembly code Christoph Hellwig
2020-09-03 14:22 ` [PATCH 12/14] x86: remove address space overrides using set_fs() Christoph Hellwig
2020-09-03 21:30 ` David Laight
2020-09-03 23:25 ` Linus Torvalds
2020-09-04 7:59 ` David Laight
2020-09-04 2:55 ` Al Viro
2020-09-04 4:41 ` Al Viro
2020-09-04 6:38 ` Christoph Hellwig
2020-09-04 7:47 ` Christoph Hellwig
2020-09-03 14:22 ` [PATCH 13/14] powerpc: use non-set_fs based maccess routines Christoph Hellwig
2020-09-03 14:22 ` [PATCH 14/14] powerpc: remove address space overrides using set_fs() Christoph Hellwig
2020-09-03 15:43 ` Christophe Leroy
2020-09-03 15:49 ` Christoph Hellwig
2020-09-03 15:56 ` Christoph Hellwig
2020-09-03 16:03 ` Christophe Leroy [this message]
2020-09-03 14:28 ` remove the last set_fs() in common code, and remove it for x86 and powerpc v3 Al Viro
2020-09-03 14:30 ` Christoph Hellwig
2020-09-03 14:36 ` Al Viro
2020-09-03 14:40 ` Christoph Hellwig
2020-09-09 17:31 ` Linus Torvalds
2020-09-09 18:40 ` Segher Boessenkool
2020-09-09 21:33 ` Linus Torvalds
2020-09-10 8:04 ` David Laight
2020-09-10 8:13 ` Christophe Leroy
2020-09-10 9:26 ` David Laight
2020-09-10 12:26 ` David Laight
2020-09-10 15:20 ` Segher Boessenkool
2020-09-10 15:31 ` David Laight
2020-09-10 17:15 ` Segher Boessenkool
2020-09-10 15:16 ` Segher Boessenkool
2020-09-10 15:44 ` Segher Boessenkool
2020-09-03 15:49 ` Linus Torvalds
2020-09-04 6:00 ` Ingo Molnar
2020-09-04 17:58 ` Alexey Dobriyan
2020-09-04 18:42 ` Linus Torvalds
2020-09-04 21:01 ` David Laight
2020-09-05 7:16 ` Christophe Leroy
2020-09-05 10:13 ` David Laight
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