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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 26 Feb 2019 14:08:58 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     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>,
        Chris Wilson <chris@...is-wilson.co.uk>, stable@...r.kernel.org
Subject: [PATCH] drm/vkms: fix use-after-free when drm_gem_handle_create() fails

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>
---
 drivers/gpu/drm/vkms/vkms_gem.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

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_device *dev,
 
 	ret = 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);
-	}
 
 	return &obj->gem;
 }
-- 
2.21.0.rc2.261.ga7da99ff1b-goog