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From: Christoph Hellwig <hch@lst.de>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Christoph Hellwig <hch@lst.de>, Nick Hu <nickhu@andestech.com>,
	Greentime Hu <green.hu@gmail.com>,
	Vincent Chen <deanbo422@gmail.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6] syscalls: use uaccess_kernel in addr_limit_user_check
Date: Tue, 21 Jul 2020 07:35:42 +0200	[thread overview]
Message-ID: <20200721053542.GA10301@lst.de> (raw)
In-Reply-To: <7fc565fe-411e-6a0b-8aaf-0bf808f0d6a9@roeck-us.net>

On Mon, Jul 20, 2020 at 10:30:30PM -0700, Guenter Roeck wrote:
> Guess I lost it somewhere. Are you saying the check was wrong all along
> and your patch fixed it ?

Oh, it is a little complicated.

Normally we have two address space limits, KERNEL_DS and USER_DS,
and they are supposed to be different.  armnommu and m68k define them
to the same value for no good reason.  That leads to:

uaccess_kernel always returning true as it does a positive check
agains KERNEL_DS, which disables a bunch of drivers like sg and
rdma, and could also lead to really strange and probably broken
results in a few places.

It also leads to the SIGKILL in addr_limit_user_check never
triggering due to the negatіve check, which is ok as the limits
never are different.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-arch@vger.kernel.org, Nick Hu <nickhu@andestech.com>,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Greentime Hu <green.hu@gmail.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vincent Chen <deanbo422@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/6] syscalls: use uaccess_kernel in addr_limit_user_check
Date: Tue, 21 Jul 2020 07:35:42 +0200	[thread overview]
Message-ID: <20200721053542.GA10301@lst.de> (raw)
In-Reply-To: <7fc565fe-411e-6a0b-8aaf-0bf808f0d6a9@roeck-us.net>

On Mon, Jul 20, 2020 at 10:30:30PM -0700, Guenter Roeck wrote:
> Guess I lost it somewhere. Are you saying the check was wrong all along
> and your patch fixed it ?

Oh, it is a little complicated.

Normally we have two address space limits, KERNEL_DS and USER_DS,
and they are supposed to be different.  armnommu and m68k define them
to the same value for no good reason.  That leads to:

uaccess_kernel always returning true as it does a positive check
agains KERNEL_DS, which disables a bunch of drivers like sg and
rdma, and could also lead to really strange and probably broken
results in a few places.

It also leads to the SIGKILL in addr_limit_user_check never
triggering due to the negatіve check, which is ok as the limits
never are different.

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http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2020-07-21  5:35 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-14 10:54 clean up address limit helpers v2 Christoph Hellwig
2020-07-14 10:54 ` Christoph Hellwig
2020-07-14 10:55 ` [PATCH 1/6] syscalls: use uaccess_kernel in addr_limit_user_check Christoph Hellwig
2020-07-14 10:55   ` Christoph Hellwig
2020-07-18  1:38   ` Guenter Roeck
2020-07-18  1:38     ` Guenter Roeck
2020-07-18  9:48     ` Christoph Hellwig
2020-07-18  9:48       ` Christoph Hellwig
2020-07-18 14:54       ` Guenter Roeck
2020-07-18 14:54         ` Guenter Roeck
2020-07-20 10:01         ` Christoph Hellwig
2020-07-20 10:01           ` Christoph Hellwig
2020-07-20 14:55           ` Guenter Roeck
2020-07-20 14:55             ` Guenter Roeck
2020-07-20 15:28             ` Peter Maydell
2020-07-20 15:28               ` Peter Maydell
2020-07-20 22:10       ` Guenter Roeck
2020-07-20 22:10         ` Guenter Roeck
2020-07-21  4:58         ` Christoph Hellwig
2020-07-21  4:58           ` Christoph Hellwig
2020-07-21  5:15           ` Guenter Roeck
2020-07-21  5:15             ` Guenter Roeck
2020-07-21  5:20             ` Christoph Hellwig
2020-07-21  5:20               ` Christoph Hellwig
2020-07-21  5:30               ` Guenter Roeck
2020-07-21  5:30                 ` Guenter Roeck
2020-07-21  5:35                 ` Christoph Hellwig [this message]
2020-07-21  5:35                   ` Christoph Hellwig
2020-07-14 10:55 ` [PATCH 2/6] nds32: use uaccess_kernel in show_regs Christoph Hellwig
2020-07-14 10:55   ` Christoph Hellwig
2020-07-14 10:55 ` [PATCH 3/6] riscv: include <asm/pgtable.h> in <asm/uaccess.h> Christoph Hellwig
2020-07-14 10:55   ` Christoph Hellwig
2020-07-14 10:55 ` [PATCH 4/6] uaccess: remove segment_eq Christoph Hellwig
2020-07-14 10:55   ` Christoph Hellwig
2020-07-14 15:27   ` Linus Torvalds
2020-07-14 15:27     ` Linus Torvalds
2020-07-14 10:55 ` [PATCH 5/6] uaccess: add force_uaccess_{begin,end} helpers Christoph Hellwig
2020-07-14 10:55   ` Christoph Hellwig
2020-07-14 15:29   ` Linus Torvalds
2020-07-14 15:29     ` Linus Torvalds
2020-07-14 10:55 ` [PATCH 6/6] exec: use force_uaccess_begin during exec and exit Christoph Hellwig
2020-07-14 10:55   ` Christoph Hellwig
2020-07-15  3:33   ` Eric W. Biederman
2020-07-15  3:33     ` Eric W. Biederman
2020-07-15  6:06     ` Christoph Hellwig
2020-07-15  6:06       ` Christoph Hellwig
2020-07-16 23:49 ` clean up address limit helpers v2 Andrew Morton
2020-07-16 23:49   ` Andrew Morton
2020-07-17  6:06   ` Christoph Hellwig
2020-07-17  6:06     ` Christoph Hellwig
2020-07-20 15:54 ` [PATCH 0/6] arm: don't call addr_limit_user_check for nommu Christoph Hellwig
2020-07-20 15:54   ` Christoph Hellwig
  -- strict thread matches above, loose matches on Subject: below --
2020-07-10 13:57 clean up address limit helpers Christoph Hellwig
2020-07-10 13:57 ` [PATCH 1/6] syscalls: use uaccess_kernel in addr_limit_user_check Christoph Hellwig
2020-07-10 13:57   ` Christoph Hellwig

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