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From: 'Christoph Hellwig' <hch@lst.de>
To: David Laight <David.Laight@ACULAB.COM>
Cc: 'Christoph Hellwig' <hch@lst.de>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Michael Ellerman <mpe@ellerman.id.au>,
	"x86@kernel.org" <x86@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 09/11] x86: remove address space overrides using set_fs()
Date: Thu, 27 Aug 2020 11:37:48 +0200	[thread overview]
Message-ID: <20200827093748.GA13887@lst.de> (raw)
In-Reply-To: <935d551809894d14965e430e05d21057@AcuMS.aculab.com>

On Mon, Aug 17, 2020 at 08:23:11AM +0000, David Laight wrote:
> From: Christoph Hellwig
> > Sent: 17 August 2020 08:32
> >
> > Stop providing the possibility to override the address space using
> > set_fs() now that there is no need for that any more.  To properly
> > handle the TASK_SIZE_MAX checking for 4 vs 5-level page tables on
> > x86 a new alternative is introduced, which just like the one in
> > entry_64.S has to use the hardcoded virtual address bits to escape
> > the fact that TASK_SIZE_MAX isn't actually a constant when 5-level
> > page tables are enabled.
> ....
> > @@ -93,7 +69,7 @@ static inline bool pagefault_disabled(void);
> >  #define access_ok(addr, size)					\
> >  ({									\
> >  	WARN_ON_IN_IRQ();						\
> > -	likely(!__range_not_ok(addr, size, user_addr_max()));		\
> > +	likely(!__range_not_ok(addr, size, TASK_SIZE_MAX));		\
> >  })
> 
> Can't that always compare against a constant even when 5-levl
> page tables are enabled on x86-64?
> 
> On x86-64 it can (probably) reduce to (addr | (addr + size)) < 0.

I'll leave that to the x86 maintainers as a future cleanup if wanted.

  reply	other threads:[~2020-08-27  9:37 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-17  7:32 remove the last set_fs() in common code, and remove it for x86 and powerpc Christoph Hellwig
2020-08-17  7:32 ` [PATCH 01/11] mem: remove duplicate ops for /dev/zero and /dev/null Christoph Hellwig
2020-08-18 19:33   ` Kees Cook
2020-08-17  7:32 ` [PATCH 02/11] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-08-18 19:34   ` Kees Cook
2020-08-17  7:32 ` [PATCH 03/11] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-08-18 19:39   ` Kees Cook
2020-08-18 19:54     ` Christoph Hellwig
2020-08-18 19:58       ` Kees Cook
2020-08-18 20:07         ` Christoph Hellwig
2020-08-17  7:32 ` [PATCH 04/11] uaccess: add infrastructure for kernel builds with set_fs() Christoph Hellwig
2020-08-18 19:40   ` Kees Cook
2020-08-17  7:32 ` [PATCH 05/11] test_bitmap: skip user bitmap tests for !CONFIG_SET_FS Christoph Hellwig
2020-08-17  7:50   ` Christophe Leroy
2020-08-17  7:52     ` Christoph Hellwig
2020-08-18 19:43   ` Kees Cook
2020-08-17  7:32 ` [PATCH 06/11] lkdtm: disable set_fs-based " Christoph Hellwig
2020-08-18 19:32   ` Kees Cook
2020-08-17  7:32 ` [PATCH 07/11] x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h Christoph Hellwig
2020-08-18 19:27   ` Kees Cook
2020-08-17  7:32 ` [PATCH 08/11] x86: make TASK_SIZE_MAX usable from assembly code Christoph Hellwig
2020-08-18 19:44   ` Kees Cook
2020-08-18 19:55     ` Christoph Hellwig
2020-08-18 19:59       ` Kees Cook
2020-08-18 20:00         ` Christoph Hellwig
2020-08-18 20:08           ` Kees Cook
2020-08-17  7:32 ` [PATCH 09/11] x86: remove address space overrides using set_fs() Christoph Hellwig
2020-08-17  8:23   ` David Laight
2020-08-27  9:37     ` 'Christoph Hellwig' [this message]
2020-08-18 19:46   ` Kees Cook
2020-08-17  7:32 ` [PATCH 10/11] powerpc: use non-set_fs based maccess routines Christoph Hellwig
2020-08-17 15:47   ` Christophe Leroy
2020-08-17  7:32 ` [PATCH 11/11] powerpc: remove address space overrides using set_fs() Christoph Hellwig
2020-08-17  7:39 ` remove the last set_fs() in common code, and remove it for x86 and powerpc Christoph Hellwig
2020-08-18 17:46 ` Christophe Leroy
2020-08-18 18:05   ` Christoph Hellwig
2020-08-18 18:23     ` Christophe Leroy
2020-08-19  7:16       ` Christophe Leroy
2020-08-19  7:22         ` iter and normal ops on /dev/zero & co, was " Christoph Hellwig

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