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From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Christoph Hellwig <hch@lst.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Michael Ellerman <mpe@ellerman.id.au>,
	x86@kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 10/10] powerpc: remove address space overrides using set_fs()
Date: Wed, 2 Sep 2020 08:15:12 +0200	[thread overview]
Message-ID: <8974838a-a0b1-1806-4a3a-e983deda67ca@csgroup.eu> (raw)
In-Reply-To: <20200827150030.282762-11-hch@lst.de>



Le 27/08/2020 à 17:00, 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>
> ---
>   arch/powerpc/Kconfig                   |  1 -
>   arch/powerpc/include/asm/processor.h   |  7 ---
>   arch/powerpc/include/asm/thread_info.h |  5 +--
>   arch/powerpc/include/asm/uaccess.h     | 62 ++++++++------------------
>   arch/powerpc/kernel/signal.c           |  3 --
>   arch/powerpc/lib/sstep.c               |  6 +--
>   6 files changed, 22 insertions(+), 62 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 7fe3531ad36a77..39727537d39701 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -8,62 +8,36 @@
>   #include <asm/extable.h>
>   #include <asm/kup.h>
>   
> -/*
> - * The fs value determines whether argument validity checking should be
> - * performed or not.  If get_fs() == USER_DS, checking is performed, with
> - * get_fs() == KERNEL_DS, checking is bypassed.
> - *
> - * For historical reasons, these macros are grossly misnamed.
> - *
> - * The fs/ds values are now the highest legal address in the "segment".
> - * This simplifies the checking in the routines below.
> - */
> -
> -#define MAKE_MM_SEG(s)  ((mm_segment_t) { (s) })
> -
> -#define KERNEL_DS	MAKE_MM_SEG(~0UL)
>   #ifdef __powerpc64__
>   /* We use TASK_SIZE_USER64 as TASK_SIZE is not constant */
> -#define USER_DS		MAKE_MM_SEG(TASK_SIZE_USER64 - 1)
> -#else
> -#define USER_DS		MAKE_MM_SEG(TASK_SIZE - 1)
> -#endif
> -
> -#define get_fs()	(current->thread.addr_limit)
> +#define TASK_SIZE_MAX		TASK_SIZE_USER64
>   
> -static inline void set_fs(mm_segment_t fs)
> +static inline bool __access_ok(unsigned long addr, unsigned long size)
>   {
> -	current->thread.addr_limit = fs;
> -	/* On user-mode return check addr_limit (fs) is correct */
> -	set_thread_flag(TIF_FSCHECK);
> +	if (addr >= TASK_SIZE_MAX)
> +		return false;
> +	/*
> +	 * This check is sufficient because there is a large enough gap between
> +	 * user addresses and the kernel addresses.
> +	 */
> +	return size <= TASK_SIZE_MAX;
>   }
> -
> -#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
> -#define user_addr_max()	(get_fs().seg)
> -
> -#ifdef __powerpc64__
> -/*
> - * This check is sufficient because there is a large enough
> - * gap between user addresses and the kernel addresses
> - */
> -#define __access_ok(addr, size, segment)	\
> -	(((addr) <= (segment).seg) && ((size) <= (segment).seg))
> -
>   #else
> +#define TASK_SIZE_MAX		TASK_SIZE
>   
> -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;
> +	if (size == 0)
> +		return false;

__access_ok() was returning true when size == 0 up to now. Any reason to 
return false now ?

> +	return size <= TASK_SIZE_MAX - addr;
>   }
> -
> -#endif
> +#endif /* __powerpc64__ */
>   
>   #define access_ok(addr, size)		\
>   	(__chk_user_ptr(addr),		\
> -	 __access_ok((__force unsigned long)(addr), (size), get_fs()))
> +	 __access_ok((unsigned long)(addr), (size)))
>   
>   /*
>    * These are the main single-value transfer routines.  They automatically

Christophe

  reply	other threads:[~2020-09-02  6:15 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-27 15:00 remove the last set_fs() in common code, and remove it for x86 and powerpc v2 Christoph Hellwig
2020-08-27 15:00 ` [PATCH 01/10] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-08-27 15:58   ` David Laight
2020-08-29  9:23     ` 'Christoph Hellwig'
     [not found]   ` <20200901064849.GI4299@shao2-debian>
2020-09-01  7:08     ` [fs] ef30fb3c60: kernel write not supported for file /sys/kernel/softlockup_panic Christoph Hellwig
2020-08-27 15:00 ` [PATCH 02/10] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-08-27 15:00 ` [PATCH 03/10] uaccess: add infrastructure for kernel builds with set_fs() Christoph Hellwig
2020-08-27 15:00 ` [PATCH 04/10] test_bitmap: skip user bitmap tests for !CONFIG_SET_FS Christoph Hellwig
2020-08-27 15:00 ` [PATCH 05/10] lkdtm: disable set_fs-based " Christoph Hellwig
2020-08-27 18:06   ` Linus Torvalds
2020-08-29  9:24     ` Christoph Hellwig
2020-09-01 18:52       ` Kees Cook
2020-09-01 18:57       ` Kees Cook
2020-09-02  8:09         ` Christoph Hellwig
2020-08-27 15:00 ` [PATCH 06/10] x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h Christoph Hellwig
2020-08-27 15:00 ` [PATCH 07/10] x86: make TASK_SIZE_MAX usable from assembly code Christoph Hellwig
2020-08-27 15:00 ` [PATCH 08/10] x86: remove address space overrides using set_fs() Christoph Hellwig
2020-08-27 18:15   ` Linus Torvalds
2020-08-29  9:25     ` Christoph Hellwig
2020-08-27 15:00 ` [PATCH 09/10] powerpc: use non-set_fs based maccess routines Christoph Hellwig
2020-08-27 15:00 ` [PATCH 10/10] powerpc: remove address space overrides using set_fs() Christoph Hellwig
2020-09-02  6:15   ` Christophe Leroy [this message]
2020-09-02 12:36     ` Christoph Hellwig
2020-09-02 13:13       ` David Laight
2020-09-02 13:24         ` Christophe Leroy
2020-09-02 13:51           ` David Laight
2020-09-02 14:12             ` Christophe Leroy
2020-09-02 15:02               ` David Laight
2020-09-02 15:17       ` Christophe Leroy
2020-09-02 18:02         ` Linus Torvalds
2020-09-03  7:11           ` Christoph Hellwig
2020-09-03  7:27             ` Christophe Leroy
2020-09-03  8:55             ` Christophe Leroy
2020-09-03  7:20           ` Christophe Leroy
2020-08-27 15:31 ` remove the last set_fs() in common code, and remove it for x86 and powerpc v2 Christoph Hellwig
2020-09-01 17:13 ` Christophe Leroy
2020-09-01 17:25   ` Al Viro
2020-09-01 17:42     ` Matthew Wilcox
2020-09-01 18:39     ` Christophe Leroy
2020-09-01 19:01     ` Christophe Leroy
2020-09-02  8:10     ` Christoph Hellwig
2020-10-27  9:29 ` [PATCH 02/10] fs: don't allow splice read/write without explicit ops David Howells
2020-10-27  9:51 ` David Howells
2020-10-27  9:54   ` Christoph Hellwig
2020-10-27 10:38   ` David Howells

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