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a=rsa-sha256; c=relaxed/relaxed; d=mail.ustc.edu.cn; s=dkim; h=Received:From:To:Cc:Subject:Date: Message-Id:MIME-Version:Content-Transfer-Encoding; bh=XcjGkHVa6C nee3IqKp4QVabZFCLc/bBbQsfdChM0o8M=; b=JxgXXgrPjt06IXfD+VfFyt55xH rfybtg0zY7Ipzrz2pOjyfe7kCglsSbH693814QChtOgpNQWSuB7N3OO3dAaFQIMx IsIdu1PxcDfXYiSRTfGLAlWO+2JVBq4p0I3wD/J3isBRHcRhKaJUbWAG+tSys/n7 /g4LCOa5RRLjhk0Ww= From: Lv Yunlong To: oleksandr_andrushchenko@epam.com, airlied@linux.ie, daniel@ffwll.ch Cc: dri-devel@lists.freedesktop.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Lv Yunlong Subject: [PATCH] gpu/xen: Fix a use after free in xen_drm_drv_init Date: Mon, 22 Mar 2021 18:46:56 -0700 Message-Id: <20210323014656.10068-1-lyl2019@mail.ustc.edu.cn> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: LkAmygAHTZySSFlgFboXAA--.232S4 X-Coremail-Antispam: 1UD129KBjvJXoW7Zw4fXw1fCFy8Xw4kWry5twb_yoW8Xw47pF 4fZFy5KrWUtws2kr15A3Wku3W5JanrKa1fGr9xA3y3Cw45ZFy09a15t34xuFyUArWfCrn5 tr9xXFyUAFyDCr7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvl14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1lnxkEFVAIw20F6cxK64vIFxWle2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xv F2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r 4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I 648v4I1lc2xSY4AK67AK6w4l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr 1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE 14v26r126r1DMIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7 IYx2IY6xkF7I0E14v26r1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvE x4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvj DU0xZFpf9x0JUmNtcUUUUU= X-CM-SenderInfo: ho1ojiyrz6zt1loo32lwfovvfxof0/ X-ZohoMail-DKIM: pass (identity @mail.ustc.edu.cn) Content-Type: text/plain; charset="utf-8" In function displback_changed, has the call chain displback_connect(front_info)->xen_drm_drv_init(front_info). We can see that drm_info is assigned to front_info->drm_info and drm_info is freed in fail branch in xen_drm_drv_init(). Later displback_disconnect(front_info) is called and it calls xen_drm_drv_fini(front_info) cause a use after free by drm_info =3D front_info->drm_info statement. My patch has done two things. First fixes the fail label which drm_info =3D kzalloc() failed and still free the drm_info. Second sets front_info->drm_info to NULL to avoid uaf. Signed-off-by: Lv Yunlong Reviewed-by: Oleksandr Andrushchenko --- drivers/gpu/drm/xen/xen_drm_front.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_= drm_front.c index 30d9adf31c84..9f14d99c763c 100644 --- a/drivers/gpu/drm/xen/xen_drm_front.c +++ b/drivers/gpu/drm/xen/xen_drm_front.c @@ -521,7 +521,7 @@ static int xen_drm_drv_init(struct xen_drm_front_info *= front_info) drm_dev =3D drm_dev_alloc(&xen_drm_driver, dev); if (IS_ERR(drm_dev)) { ret =3D PTR_ERR(drm_dev); - goto fail; + goto fail_dev; } =20 drm_info->drm_dev =3D drm_dev; @@ -551,8 +551,10 @@ static int xen_drm_drv_init(struct xen_drm_front_info = *front_info) drm_kms_helper_poll_fini(drm_dev); drm_mode_config_cleanup(drm_dev); drm_dev_put(drm_dev); -fail: +fail_dev: kfree(drm_info); + front_info->drm_info =3D NULL; +fail: return ret; } =20 --=20 2.25.1