From: Dan Carpenter <dan.carpenter@oracle.com>
To: syzbot <syzbot+0dc4444774d419e916c8@syzkaller.appspotmail.com>
Cc: robdclark@chromium.org, davem@davemloft.net, airlied@linux.ie,
netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com,
linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org,
chris@chris-wilson.co.uk, linaro-mm-sig@lists.linaro.org,
eric@anholt.net, seanpaul@chromium.org,
dri-devel@lists.freedesktop.org, daniel@ffwll.ch,
alexander.deucher@amd.com, linux-media@vger.kernel.org,
sumit.semwal@linaro.org, christian.koenig@amd.com,
emil.velikov@collabora.com
Subject: Re: KASAN: use-after-free Read in vgem_gem_dumb_create
Date: Sat, 1 Feb 2020 08:56:12 +0300 [thread overview]
Message-ID: <20200201055612.GF1778@kadam> (raw)
In-Reply-To: <000000000000ae2f81059d7716b8@google.com>
I don't totally understand the stack trace but I do see a double free
bug.
drivers/gpu/drm/vgem/vgem_drv.c
186 static struct drm_gem_object *vgem_gem_create(struct drm_device *dev,
187 struct drm_file *file,
188 unsigned int *handle,
189 unsigned long size)
190 {
191 struct drm_vgem_gem_object *obj;
192 int ret;
193
194 obj = __vgem_gem_create(dev, size);
obj->base.handle_count is zero.
195 if (IS_ERR(obj))
196 return ERR_CAST(obj);
197
198 ret = drm_gem_handle_create(file, &obj->base, handle);
We bump it +1 and then the error handling calls
drm_gem_object_handle_put_unlocked(obj);
which calls drm_gem_object_put_unlocked(); which frees obj.
199 drm_gem_object_put_unlocked(&obj->base);
So this is a double free. Could someone check my thinking and send
a patch? It's just a one liner. Otherwise I can send it on Monday.
200 if (ret)
201 return ERR_PTR(ret);
202
203 return &obj->base;
204 }
regards,
dan carpenter
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next prev parent reply other threads:[~2020-02-01 5:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 22:28 KASAN: use-after-free Read in vgem_gem_dumb_create syzbot
2020-02-01 5:56 ` Dan Carpenter [this message]
2020-02-02 4:38 ` syzbot
2020-02-02 13:19 ` Daniel Vetter
2020-02-03 9:06 ` Dan Carpenter
2020-02-03 15:08 ` Christian König
-- strict thread matches above, loose matches on Subject: below --
2020-02-01 4:32 Hillf Danton
2020-02-01 6:17 ` Dan Carpenter
2020-02-01 9:02 ` Hillf Danton
2020-02-01 16:25 ` Dan Carpenter
2020-02-02 13:17 ` Daniel Vetter
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