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From: Eric Biggers <ebiggers@kernel.org>
To: dri-devel@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	linux-kernel@vger.kernel.org,
	syzbot+e73f2fb5ed5a5df36d33@syzkaller.appspotmail.com,
	Laura Abbott <labbott@redhat.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	stable@vger.kernel.org
Subject: [PATCH v2] drm/vgem: fix use-after-free when drm_gem_handle_create() fails
Date: Tue, 26 Feb 2019 13:44:51 -0800
Message-ID: <20190226214451.195123-1-ebiggers@kernel.org> (raw)
In-Reply-To: <20190226213053.GC218103@gmail.com>

From: Eric Biggers <ebiggers@google.com>

If drm_gem_handle_create() fails in vgem_gem_create(), then the
drm_vgem_gem_object is freed twice: once when the reference is dropped
by drm_gem_object_put_unlocked(), and again by __vgem_gem_destroy().

This was hit by syzkaller using fault injection.

Fix it by skipping the second free.

Reported-by: syzbot+e73f2fb5ed5a5df36d33@syzkaller.appspotmail.com
Fixes: af33a9190d02 ("drm/vgem: Enable dmabuf import interfaces")
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/gpu/drm/vgem/vgem_drv.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index 5930facd6d2d8..11a8f99ba18c5 100644
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -191,13 +191,9 @@ static struct drm_gem_object *vgem_gem_create(struct drm_device *dev,
 	ret = drm_gem_handle_create(file, &obj->base, handle);
 	drm_gem_object_put_unlocked(&obj->base);
 	if (ret)
-		goto err;
+		return ERR_PTR(ret);
 
 	return &obj->base;
-
-err:
-	__vgem_gem_destroy(obj);
-	return ERR_PTR(ret);
 }
 
 static int vgem_gem_dumb_create(struct drm_file *file, struct drm_device *dev,
-- 
2.21.0.rc2.261.ga7da99ff1b-goog

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <00000000000053fea105791276d8@google.com>
2018-10-29 11:51 ` KASAN: use-after-free Read in drm_gem_object_release Dmitry Vyukov
2019-02-26 20:47   ` [PATCH] drm/vgem: fix use-after-free when drm_gem_handle_create() fails Eric Biggers
2019-02-26 21:01     ` Chris Wilson
2019-02-26 21:30       ` Eric Biggers
2019-02-26 21:44         ` Eric Biggers [this message]
2019-02-27 23:52           ` [PATCH v2] " Laura Abbott
2019-03-04 23:24           ` Rodrigo Siqueira
2019-02-26 22:08         ` [PATCH] drm/vkms: " Eric Biggers
2019-02-26 22:14           ` Chris Wilson
2019-02-27 23:12           ` Rodrigo Siqueira
2019-02-28  6:41             ` Dmitry Vyukov
2019-03-04 23:23               ` Rodrigo Siqueira
2019-03-05 14:25                 ` Dmitry Vyukov
2019-03-10 15:36                   ` Rodrigo Siqueira
2019-02-27 13:23     ` [PATCH] drm/vgem: " Sasha Levin

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