| Message ID | 20200124141356.365bgzg2lp3tjedm@kili.mountain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | media: usbvision: Fix a use after free in v4l2_release() | expand |
On 1/24/20 3:13 PM, Dan Carpenter wrote: > Syzbot triggered a use after free in v5.5-rc6: > > BUG: KASAN: use-after-free in v4l2_release+0x2f1/0x390 drivers/media/v4l2-core/v4l2-dev.c:459 > > Allocated by task 94: > usbvision_alloc drivers/media/usb/usbvision/usbvision-video.c:1315 [inline] > usbvision_probe.cold+0x5c5/0x1f21 drivers/media/usb/usbvision/usbvision-video.c:1469 > > Freed by task 1913: > kfree+0xd5/0x300 mm/slub.c:3957 > usbvision_release+0x181/0x1c0 drivers/media/usb/usbvision/usbvision-video.c:1364 > usbvision_radio_close.cold+0x2b/0x74 drivers/media/usb/usbvision/usbvision-video.c:1130 > v4l2_release+0x2e7/0x390 drivers/media/v4l2-core/v4l2-dev.c:455 > > The problem is that the v4l2_release() calls usbvision_release() which > frees "usbvision" but v4l2_release() still wants to use > "usbvision->vdev". One solution is to make this devm_ allocated memory > so the memory isn't freed until later. devm_ allocated memory is freed after disconnect, so I doubt this will help, or at best it will just move the problem elsewhere. The right approach would be to use the release() callback from struct v4l2_device: that's called when the very last open filehandle is closed. But I'm not sure if it is worth the effort. The usbvision driver is a mess and personally I think it should be deprecated. Regards, Hans > > Reported-by: syzbot+75287f75e2fedd69d680@syzkaller.appspotmail.com > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > --- > I copied this idea from a different driver, but I haven't tested it. > I wanted to try the #syz fix command to see if it works. > > drivers/media/usb/usbvision/usbvision-video.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/media/usb/usbvision/usbvision-video.c b/drivers/media/usb/usbvision/usbvision-video.c > index 93d36aab824f..07b4763062c4 100644 > --- a/drivers/media/usb/usbvision/usbvision-video.c > +++ b/drivers/media/usb/usbvision/usbvision-video.c > @@ -1312,7 +1312,7 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, > { > struct usb_usbvision *usbvision; > > - usbvision = kzalloc(sizeof(*usbvision), GFP_KERNEL); > + usbvision = devm_kzalloc(&dev->dev, sizeof(*usbvision), GFP_KERNEL); > if (!usbvision) > return NULL; > > @@ -1336,7 +1336,6 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, > v4l2_ctrl_handler_free(&usbvision->hdl); > v4l2_device_unregister(&usbvision->v4l2_dev); > err_free: > - kfree(usbvision); > return NULL; > } > > @@ -1361,7 +1360,6 @@ static void usbvision_release(struct usb_usbvision *usbvision) > > v4l2_ctrl_handler_free(&usbvision->hdl); > v4l2_device_unregister(&usbvision->v4l2_dev); > - kfree(usbvision); > > PDEBUG(DBG_PROBE, "success"); > } >
Hi Hans, On Fri, Feb 14, 2020 at 11:06:36AM +0100, Hans Verkuil wrote: > On 1/24/20 3:13 PM, Dan Carpenter wrote: > > Syzbot triggered a use after free in v5.5-rc6: > > > > BUG: KASAN: use-after-free in v4l2_release+0x2f1/0x390 drivers/media/v4l2-core/v4l2-dev.c:459 > > > > Allocated by task 94: > > usbvision_alloc drivers/media/usb/usbvision/usbvision-video.c:1315 [inline] > > usbvision_probe.cold+0x5c5/0x1f21 drivers/media/usb/usbvision/usbvision-video.c:1469 > > > > Freed by task 1913: > > kfree+0xd5/0x300 mm/slub.c:3957 > > usbvision_release+0x181/0x1c0 drivers/media/usb/usbvision/usbvision-video.c:1364 > > usbvision_radio_close.cold+0x2b/0x74 drivers/media/usb/usbvision/usbvision-video.c:1130 > > v4l2_release+0x2e7/0x390 drivers/media/v4l2-core/v4l2-dev.c:455 > > > > The problem is that the v4l2_release() calls usbvision_release() which > > frees "usbvision" but v4l2_release() still wants to use > > "usbvision->vdev". One solution is to make this devm_ allocated memory > > so the memory isn't freed until later. > > devm_ allocated memory is freed after disconnect, so I doubt this will help, or at > best it will just move the problem elsewhere. Yes, devm_*alloc is evil :-( It has spread to many drivers and is used incorrectly in most cases. > The right approach would be to use the release() callback from struct v4l2_device: > that's called when the very last open filehandle is closed. Hillf Danton has sent a patch to do so in the "Re: KASAN: use-after-free Read in v4l2_release (3)" thread. Have you seen it ? > But I'm not sure if it is worth the effort. The usbvision driver is a mess and > personally I think it should be deprecated. I agree. > > Reported-by: syzbot+75287f75e2fedd69d680@syzkaller.appspotmail.com > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > > --- > > I copied this idea from a different driver, but I haven't tested it. > > I wanted to try the #syz fix command to see if it works. > > > > drivers/media/usb/usbvision/usbvision-video.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/drivers/media/usb/usbvision/usbvision-video.c b/drivers/media/usb/usbvision/usbvision-video.c > > index 93d36aab824f..07b4763062c4 100644 > > --- a/drivers/media/usb/usbvision/usbvision-video.c > > +++ b/drivers/media/usb/usbvision/usbvision-video.c > > @@ -1312,7 +1312,7 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, > > { > > struct usb_usbvision *usbvision; > > > > - usbvision = kzalloc(sizeof(*usbvision), GFP_KERNEL); > > + usbvision = devm_kzalloc(&dev->dev, sizeof(*usbvision), GFP_KERNEL); > > if (!usbvision) > > return NULL; > > > > @@ -1336,7 +1336,6 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, > > v4l2_ctrl_handler_free(&usbvision->hdl); > > v4l2_device_unregister(&usbvision->v4l2_dev); > > err_free: > > - kfree(usbvision); > > return NULL; > > } > > > > @@ -1361,7 +1360,6 @@ static void usbvision_release(struct usb_usbvision *usbvision) > > > > v4l2_ctrl_handler_free(&usbvision->hdl); > > v4l2_device_unregister(&usbvision->v4l2_dev); > > - kfree(usbvision); > > > > PDEBUG(DBG_PROBE, "success"); > > }
On 2/14/20 12:22 PM, Laurent Pinchart wrote: > Hi Hans, > > On Fri, Feb 14, 2020 at 11:06:36AM +0100, Hans Verkuil wrote: >> On 1/24/20 3:13 PM, Dan Carpenter wrote: >>> Syzbot triggered a use after free in v5.5-rc6: >>> >>> BUG: KASAN: use-after-free in v4l2_release+0x2f1/0x390 drivers/media/v4l2-core/v4l2-dev.c:459 >>> >>> Allocated by task 94: >>> usbvision_alloc drivers/media/usb/usbvision/usbvision-video.c:1315 [inline] >>> usbvision_probe.cold+0x5c5/0x1f21 drivers/media/usb/usbvision/usbvision-video.c:1469 >>> >>> Freed by task 1913: >>> kfree+0xd5/0x300 mm/slub.c:3957 >>> usbvision_release+0x181/0x1c0 drivers/media/usb/usbvision/usbvision-video.c:1364 >>> usbvision_radio_close.cold+0x2b/0x74 drivers/media/usb/usbvision/usbvision-video.c:1130 >>> v4l2_release+0x2e7/0x390 drivers/media/v4l2-core/v4l2-dev.c:455 >>> >>> The problem is that the v4l2_release() calls usbvision_release() which >>> frees "usbvision" but v4l2_release() still wants to use >>> "usbvision->vdev". One solution is to make this devm_ allocated memory >>> so the memory isn't freed until later. >> >> devm_ allocated memory is freed after disconnect, so I doubt this will help, or at >> best it will just move the problem elsewhere. > > Yes, devm_*alloc is evil :-( It has spread to many drivers and is used > incorrectly in most cases. > >> The right approach would be to use the release() callback from struct v4l2_device: >> that's called when the very last open filehandle is closed. > > Hillf Danton has sent a patch to do so in the "Re: KASAN: use-after-free > Read in v4l2_release (3)" thread. Have you seen it ? Ah, that was never mailed to linux-media, so never ended up in patchwork. And if it ain't in patchwork, then I don't know about it :-) Hillf, if you want your patch to be merged, then make sure it is CC-ed to linux-media as well. Regards, Hans > >> But I'm not sure if it is worth the effort. The usbvision driver is a mess and >> personally I think it should be deprecated. > > I agree. > >>> Reported-by: syzbot+75287f75e2fedd69d680@syzkaller.appspotmail.com >>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> >>> --- >>> I copied this idea from a different driver, but I haven't tested it. >>> I wanted to try the #syz fix command to see if it works. >>> >>> drivers/media/usb/usbvision/usbvision-video.c | 4 +--- >>> 1 file changed, 1 insertion(+), 3 deletions(-) >>> >>> diff --git a/drivers/media/usb/usbvision/usbvision-video.c b/drivers/media/usb/usbvision/usbvision-video.c >>> index 93d36aab824f..07b4763062c4 100644 >>> --- a/drivers/media/usb/usbvision/usbvision-video.c >>> +++ b/drivers/media/usb/usbvision/usbvision-video.c >>> @@ -1312,7 +1312,7 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, >>> { >>> struct usb_usbvision *usbvision; >>> >>> - usbvision = kzalloc(sizeof(*usbvision), GFP_KERNEL); >>> + usbvision = devm_kzalloc(&dev->dev, sizeof(*usbvision), GFP_KERNEL); >>> if (!usbvision) >>> return NULL; >>> >>> @@ -1336,7 +1336,6 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, >>> v4l2_ctrl_handler_free(&usbvision->hdl); >>> v4l2_device_unregister(&usbvision->v4l2_dev); >>> err_free: >>> - kfree(usbvision); >>> return NULL; >>> } >>> >>> @@ -1361,7 +1360,6 @@ static void usbvision_release(struct usb_usbvision *usbvision) >>> >>> v4l2_ctrl_handler_free(&usbvision->hdl); >>> v4l2_device_unregister(&usbvision->v4l2_dev); >>> - kfree(usbvision); >>> >>> PDEBUG(DBG_PROBE, "success"); >>> } >
On 2/14/20 1:14 PM, Hillf Danton wrote: > > On Fri, 14 Feb 2020 12:30:29 +0100 Hans Verkuil wrote: >> >> Hillf, if you want your patch to be merged, then make sure it is CC-ed to >> linux-media as well. > > Please pick it up if it makes a sense to you and it was sent with > linux-media added on the Cc list as it is known for a while that > my mail agent is rejected @vger.kernel.org for what I am not clear > about. It makes my day occasionally :P I don't I ever received the full patch, only replies to your patch. Please mail your patch directly to me so I have a clean version. Regards, Hans > > Thanks > Hillf >
On 2/14/20 1:48 PM, Hillf Danton wrote: > > On Fri, 14 Feb 2020 13:21:03 +0100 Hans Verkuil wrote: >> On 2/14/20 1:14 PM, Hillf Danton wrote: >>> >>> On Fri, 14 Feb 2020 12:30:29 +0100 Hans Verkuil wrote: >>>> >>>> Hillf, if you want your patch to be merged, then make sure it is CC-ed to >>>> linux-media as well. >>> >>> Please pick it up if it makes a sense to you and it was sent with >>> linux-media added on the Cc list as it is known for a while that >>> my mail agent is rejected @vger.kernel.org for what I am not clear >>> about. It makes my day occasionally :P >> >> I don't I ever received the full patch, only replies to your patch. >> > > ========= > Please take a look at the Cc tag in the snippet from > https://lore.kernel.org/lkml/b1d071e2-0428-a08c-392d-3ca5d4a7e710@xs4all.nl/T/#m13f2c16b7cd1892f6a0b58b72ce37979cb6940b9 > > >> Subject: [PATCH] media: usbvision: add the release callback for video device >> From: Hillf Danton <hdanton@sina.com> >> >> To fix the UAF syzbot reported, >> >> BUG: KASAN: use-after-free in v4l2_release+0x2f1/0x390 drivers/media/v4l2-core/v4l2-dev.c:459 >> >> a release cb which is a simple wrapper of usbvision_release() is added >> for releasing resources as the last reference to the usbvision video >> device goes away. >> >> Reported-by: syzbot <syzbot+75287f75e2fedd69d680@syzkaller.appspotmail.com> >> Fixes: 2aa689dd8057 ("[media] usbvision: embed video_device") >> Cc: Hans Verkuil <hans.verkuil@cisco.com> Ah, my work email. And I always delete posts mailed to that if it is also CC-ed to linux-media. Which didn't actually arrive there in your case. And it's no longer in my trash folder either. So please mail me a properly formatted patch so I can forward it to linux-media for you. Regards, Hans >> Signed-off-by: Hillf Danton <hdanton@sina.com> >> --- > ========= > >> Please mail your patch directly to me so I have a clean version. >
diff --git a/drivers/media/usb/usbvision/usbvision-video.c b/drivers/media/usb/usbvision/usbvision-video.c index 93d36aab824f..07b4763062c4 100644 --- a/drivers/media/usb/usbvision/usbvision-video.c +++ b/drivers/media/usb/usbvision/usbvision-video.c @@ -1312,7 +1312,7 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, { struct usb_usbvision *usbvision; - usbvision = kzalloc(sizeof(*usbvision), GFP_KERNEL); + usbvision = devm_kzalloc(&dev->dev, sizeof(*usbvision), GFP_KERNEL); if (!usbvision) return NULL; @@ -1336,7 +1336,6 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev, v4l2_ctrl_handler_free(&usbvision->hdl); v4l2_device_unregister(&usbvision->v4l2_dev); err_free: - kfree(usbvision); return NULL; } @@ -1361,7 +1360,6 @@ static void usbvision_release(struct usb_usbvision *usbvision) v4l2_ctrl_handler_free(&usbvision->hdl); v4l2_device_unregister(&usbvision->v4l2_dev); - kfree(usbvision); PDEBUG(DBG_PROBE, "success"); }
Syzbot triggered a use after free in v5.5-rc6: BUG: KASAN: use-after-free in v4l2_release+0x2f1/0x390 drivers/media/v4l2-core/v4l2-dev.c:459 Allocated by task 94: usbvision_alloc drivers/media/usb/usbvision/usbvision-video.c:1315 [inline] usbvision_probe.cold+0x5c5/0x1f21 drivers/media/usb/usbvision/usbvision-video.c:1469 Freed by task 1913: kfree+0xd5/0x300 mm/slub.c:3957 usbvision_release+0x181/0x1c0 drivers/media/usb/usbvision/usbvision-video.c:1364 usbvision_radio_close.cold+0x2b/0x74 drivers/media/usb/usbvision/usbvision-video.c:1130 v4l2_release+0x2e7/0x390 drivers/media/v4l2-core/v4l2-dev.c:455 The problem is that the v4l2_release() calls usbvision_release() which frees "usbvision" but v4l2_release() still wants to use "usbvision->vdev". One solution is to make this devm_ allocated memory so the memory isn't freed until later. Reported-by: syzbot+75287f75e2fedd69d680@syzkaller.appspotmail.com Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> --- I copied this idea from a different driver, but I haven't tested it. I wanted to try the #syz fix command to see if it works. drivers/media/usb/usbvision/usbvision-video.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)