linux-kernel - Use of copy_from_user in msm_gem_submit.c while holding a spin

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Message-ID: <57B44D2E.2030301@oracle.com>
Date:	Wed, 17 Aug 2016 17:10:30 +0530
From:	Vaishali Thakkar <vaishali.thakkar@...cle.com>
To:	Rob Clark <robdclark@...il.com>, David Airlie <airlied@...ux.ie>,
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Use of copy_from_user in msm_gem_submit.c while holding a spin_lock

Hello,

I was wondering about the call to copy_from_user in function submit_lookup_objects for drive
/gpu/drm/msm/msm_gem_submit.c  It calls copy_from_user[1] in a spin_lock, which is not normally
allowed, due to the possibility of a deadlock.  

Is there some reason that I am overlooking why it is OK in this case? Is there some code in the
same file which ensures that page fault will not occur when we are calling the function holding
spin_lock?

Thank you.

[1] http://lxr.free-electrons.com/source/drivers/gpu/drm/msm/msm_gem_submit.c#L85

-- 
Vaishali