From: Jani Nikula <jani.nikula@linux.intel.com>
To: sohu0106 <sohu0106@126.com>,
joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: Linux kernel: drivers/gpu/drm/i915/i915_gem.c: i915_gem_pread_ioctl similar Double-Fetch bug
Date: Mon, 18 Dec 2017 10:04:59 +0200 [thread overview]
Message-ID: <87efnspil0.fsf@intel.com> (raw)
In-Reply-To: <1adb515b.3e98.1605fbfb6ec.Coremail.sohu0106@126.com>
On Sat, 16 Dec 2017, sohu0106 <sohu0106@126.com> wrote:
> I found a similar Double-Fetch bug in drivers/gpu/drm/i915/i915_gem.c
> when I was examining the source code.
Similar to what?
> In function i915_gem_pread_ioctl(), the driver check user space data
> by pointer data_ptr via access_ok() in line 694, and after run a
> while, in function shmem_pread_slow in line 657 or shmem_pread_fast in
> line 639, finally it use __copy_to_user with no check user space
> pointer.
>
> If the args->data_ptr is modified by a user thread under race
> condition between the check and __copy_to_user operations, for example
> changing to a kernel address, this will lead to Arbitrary kernel
> address writing(caused by __copy_to_user() ).
See drm_ioctl() for why this is not a possible scenario.
BR,
Jani.
--
Jani Nikula, Intel Open Source Technology Center
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next prev parent reply other threads:[~2017-12-18 8:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-16 14:34 Linux kernel: drivers/gpu/drm/i915/i915_gem.c: i915_gem_pread_ioctl similar Double-Fetch bug sohu0106
2017-12-18 8:04 ` Jani Nikula [this message]
2017-12-18 11:48 ` 回复: " sohu0106
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