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To:     Eric Biggers <ebiggers@kernel.org>, dri-devel@lists.freedesktop.org
From:   Chris Wilson <chris@chris-wilson.co.uk>
In-Reply-To: <20190226220858.214438-1-ebiggers@kernel.org>
Cc:     syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        linux-kernel@vger.kernel.org,
        Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
        Haneen Mohammed <hamohammed.sa@gmail.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>, stable@vger.kernel.org
References: <20190226213053.GC218103@gmail.com>
 <20190226220858.214438-1-ebiggers@kernel.org>
Message-ID: <155121928860.5956.12770996408502874761@skylake-alporthouse-com>
User-Agent: alot/0.6
Subject: Re: [PATCH] drm/vkms: fix use-after-free when drm_gem_handle_create() fails
Date:   Tue, 26 Feb 2019 22:14:49 +0000
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Quoting Eric Biggers (2019-02-26 22:08:58)
> From: Eric Biggers <ebiggers@google.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@gmail.com>
> Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris