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Wed, 27 Feb 2019 15:12:05 -0800 (PST) Date: Wed, 27 Feb 2019 20:12:02 -0300 From: Rodrigo Siqueira To: Eric Biggers Cc: dri-devel@lists.freedesktop.org, syzkaller-bugs , linux-kernel@vger.kernel.org, Haneen Mohammed , Daniel Vetter , Chris Wilson , stable@vger.kernel.org Subject: Re: [PATCH] drm/vkms: fix use-after-free when drm_gem_handle_create() fails Message-ID: <20190227231202.tycdbcqtk5ylwp4k@smtp.gmail.com> References: <20190226213053.GC218103@gmail.com> <20190226220858.214438-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="zv4pfadv7tlm7aiw" Content-Disposition: inline In-Reply-To: <20190226220858.214438-1-ebiggers@kernel.org> User-Agent: NeoMutt/20180716 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org --zv4pfadv7tlm7aiw Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 02/26, Eric Biggers wrote: > From: Eric Biggers >=20 > 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(). >=20 > Fix it by skipping the second release and free. >=20 > 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. >=20 > Fixes: 559e50fd34d1 ("drm/vkms: Add dumb operations") > Cc: Rodrigo Siqueira > Cc: Haneen Mohammed > Cc: Daniel Vetter > Cc: Chris Wilson > Cc: stable@vger.kernel.org > Signed-off-by: Eric Biggers > --- > drivers/gpu/drm/vkms/vkms_gem.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) >=20 > diff --git a/drivers/gpu/drm/vkms/vkms_gem.c b/drivers/gpu/drm/vkms/vkms_= gem.c > index 138b0bb325cf9..69048e73377dc 100644 > --- a/drivers/gpu/drm/vkms/vkms_gem.c > +++ b/drivers/gpu/drm/vkms/vkms_gem.c > @@ -111,11 +111,8 @@ struct drm_gem_object *vkms_gem_create(struct drm_de= vice *dev, > =20 > ret =3D drm_gem_handle_create(file, &obj->gem, handle); > drm_gem_object_put_unlocked(&obj->gem); > - if (ret) { > - drm_gem_object_release(&obj->gem); > - kfree(obj); > + if (ret) > return ERR_PTR(ret); > - } > =20 > return &obj->gem; > } > --=20 > 2.21.0.rc2.261.ga7da99ff1b-goog >=20 Hi, Thanks for your patch! :) The patch looks good for me. I also tested it under the IGT tests on my local VM and everything was fine. Reviewed-by: Rodrigo Siqueira --=20 Rodrigo Siqueira https://siqueira.tech Graduate Student Department of Computer Science University of S=E3o Paulo --zv4pfadv7tlm7aiw Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE4tZ+ii1mjMCMQbfkWJzP/comvP8FAlx3GUIACgkQWJzP/com vP8ashAAjVUU9uyTdgnZhM9fHdtKxqgp5lN+Rr6GejyOyjFgNVusANtf2Ed+7ucz 9wq6NfRRZotGTtj0MBSUVE6lwYmkMkE9XS0CRtwrt4EnDFy14V7u1JBuoMw3hDCo RZ+P51j0vVERvCiaBP+yCdgcP+ih+y25TmIPaSQonFGy8cFhU+HxjNUT0NdS85M2 /JvaBjgzoE978YAKZJr3WQzyzF8EHz5zJVfBeVJez6VSF1oVGXZbGfy7nwRv8twH 1JnlnP/8/7Uglo7EUtS8nWvoeN253JYLeeOOmTiXlT4QXfrxxMmzwAh8ArL2bgEe 3JYDwxS3rzxUj7iQPD+HfRFg/R5QkBUoGaAhSrYSImO0OWNrADk+oV47DNzRn6Ww Cq6sKdBWpzpfHpYkJfx01x4dEA7kNonVdg3v9LgRmTh63El7Yl41UbU8zAELpRrB R2oBlVqC5cSMfKAAduEqXa14uMjd5mzA5rrqSzvLm8nI6wk++n/uOmPnAQVCflBb PkxXO4ic0SKolFGL1/lstiVfJbqBsK1yPRb/SuRJdgeDsARy0xYIpav8PKGVg4gm uu5+vYJ+X5RCGNn8jVMIZ9dgi3bySnwC/Jqs1VDuMm30lsiOXDXlmjzd/FfZNJ04 s4nq9umM/YTaMo3XP2hBVAHZ5SX+3KZXNgZesiJL8wONOuF+vyw= =XvvV -----END PGP SIGNATURE----- --zv4pfadv7tlm7aiw--