From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
airlied@linux.ie, daniel@ffwll.ch, torvalds@linux-foundation.org,
viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
keescook@chromium.org, hpa@zytor.com
Cc: linux-arch@vger.kernel.org, linux-mm@kvack.org,
intel-gfx@lists.freedesktop.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/5] uaccess: Add user_read_access_begin/end and user_write_access_begin/end
Date: Fri, 29 May 2020 14:20:23 +1000 (AEST) [thread overview]
Message-ID: <49YBF35KWQz9sSr@ozlabs.org> (raw)
In-Reply-To: <36e43241c7f043a24b5069e78c6a7edd11043be5.1585898438.git.christophe.leroy@c-s.fr>
On Fri, 2020-04-03 at 07:20:50 UTC, Christophe Leroy wrote:
> Some architectures like powerpc64 have the capability to separate
> read access and write access protection.
> For get_user() and copy_from_user(), powerpc64 only open read access.
> For put_user() and copy_to_user(), powerpc64 only open write access.
> But when using unsafe_get_user() or unsafe_put_user(),
> user_access_begin open both read and write.
>
> Other architectures like powerpc book3s 32 bits only allow write
> access protection. And on this architecture protection is an heavy
> operation as it requires locking/unlocking per segment of 256Mbytes.
> On those architecture it is therefore desirable to do the unlocking
> only for write access. (Note that book3s/32 ranges from very old
> powermac from the 90's with powerpc 601 processor, till modern
> ADSL boxes with PowerQuicc II processors for instance so it
> is still worth considering.)
>
> In order to avoid any risk based of hacking some variable parameters
> passed to user_access_begin/end that would allow hacking and
> leaving user access open or opening too much, it is preferable to
> use dedicated static functions that can't be overridden.
>
> Add a user_read_access_begin and user_read_access_end to only open
> read access.
>
> Add a user_write_access_begin and user_write_access_end to only open
> write access.
>
> By default, when undefined, those new access helpers default on the
> existing user_access_begin and user_access_end.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Reviewed-by: Kees Cook <keescook@chromium.org>
Applied to powerpc topic/uaccess, thanks.
https://git.kernel.org/powerpc/c/999a22890cb183b918e4372395d24426a755cef2
cheers
prev parent reply other threads:[~2020-05-29 4:22 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-03 7:20 [PATCH v2 1/5] uaccess: Add user_read_access_begin/end and user_write_access_begin/end Christophe Leroy
2020-04-03 7:20 ` [PATCH v2 2/5] uaccess: Selectively open read or write user access Christophe Leroy
2020-05-29 4:20 ` Michael Ellerman
2020-04-03 7:20 ` [PATCH v2 3/5] drm/i915/gem: Replace user_access_begin by user_write_access_begin Christophe Leroy
2020-05-29 4:20 ` Michael Ellerman
2020-04-03 7:20 ` [PATCH v2 4/5] powerpc/uaccess: Implement user_read_access_begin and user_write_access_begin Christophe Leroy
2020-05-29 4:24 ` Michael Ellerman
2020-04-03 7:20 ` [PATCH v2 5/5] uaccess: Rename user_access_begin/end() to user_full_access_begin/end() Christophe Leroy
2020-04-03 18:01 ` Linus Torvalds
2020-04-03 20:52 ` Al Viro
2020-04-21 2:49 ` Al Viro
2020-04-21 9:12 ` Russell King - ARM Linux admin
2020-04-21 18:34 ` Linus Torvalds
2020-04-05 18:47 ` Christophe Leroy
2020-04-04 6:20 ` kbuild test robot
2020-04-04 7:17 ` kbuild test robot
2020-05-29 4:20 ` Michael Ellerman [this message]
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