linux-kernel - Re: [PATCH] drm/vkms: fix use-after-free when drm_gem_handle

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Date:   Tue, 26 Feb 2019 22:14:49 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Eric Biggers <ebiggers@...nel.org>, dri-devel@...ts.freedesktop.org
Cc:     syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        linux-kernel@...r.kernel.org,
        Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
        Haneen Mohammed <hamohammed.sa@...il.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>, stable@...r.kernel.org
Subject: Re: [PATCH] drm/vkms: fix use-after-free when drm_gem_handle_create() fails

Quoting Eric Biggers (2019-02-26 22:08:58)
> From: Eric Biggers <ebiggers@...gle.com>
> 
> If drm_gem_handle_create() fails in vkms_gem_create(), then the
> vkms_gem_object is freed twice: once when the reference is dropped by
> drm_gem_object_put_unlocked(), and again by the extra calls to
> drm_gem_object_release() and kfree().
> 
> Fix it by skipping the second release and free.
> 
> This bug was originally found in the vgem driver by syzkaller using
> fault injection, but I noticed it's also present in the vkms driver.
> 
> Fixes: 559e50fd34d1 ("drm/vkms: Add dumb operations")
> Cc: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
> Cc: Haneen Mohammed <hamohammed.sa@...il.com>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Cc: Chris Wilson <chris@...is-wilson.co.uk>
> Cc: stable@...r.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
-Chris