[PATCH] usbhid: fix info leak in hid_submit_ctrl

[PATCH] usbhid: fix info leak in hid_submit_ctrl

[Anirudh Rayabharam]

In hid_submit_ctrl(), the way of calculating the report length doesn't
take into account that report->size can be zero. When running the
syzkaller reproducer, a report of size 0 causes hid_submit_ctrl) to
calculate transfer_buffer_length as 16384. When this urb is passed to
the usb core layer, KMSAN reports an info leak of 16384 bytes.

To fix this, first modify hid_report_len() to account for the zero
report size case by using DIV_ROUND_UP for the division. Then, call it
from hid_submit_ctrl().

Reported-by: syzbot+7c2bb71996f95a82524c@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
---
 drivers/hid/usbhid/hid-core.c | 2 +-
 include/linux/hid.h           | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index 86257ce6d619..4e9077363c96 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -374,7 +374,7 @@ static int hid_submit_ctrl(struct hid_device *hid)
 	raw_report = usbhid->ctrl[usbhid->ctrltail].raw_report;
 	dir = usbhid->ctrl[usbhid->ctrltail].dir;
 
-	len = ((report->size - 1) >> 3) + 1 + (report->id > 0);
+	len = hid_report_len(report);
 	if (dir == USB_DIR_OUT) {
 		usbhid->urbctrl->pipe = usb_sndctrlpipe(hid_to_usb_dev(hid), 0);
 		usbhid->urbctrl->transfer_buffer_length = len;
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 271021e20a3f..10e922cee4eb 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1167,8 +1167,7 @@ static inline void hid_hw_wait(struct hid_device *hdev)
  */
 static inline u32 hid_report_len(struct hid_report *report)
 {
-	/* equivalent to DIV_ROUND_UP(report->size, 8) + !!(report->id > 0) */
-	return ((report->size - 1) >> 3) + 1 + (report->id > 0);
+	return DIV_ROUND_UP(report->size, 8) + (report->id > 0);
 }
 
 int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
-- 
2.26.2

Re: [PATCH] usbhid: fix info leak in hid_submit_ctrl

[Jiri Kosina]

On Sun, 25 Apr 2021, Anirudh Rayabharam wrote:

> In hid_submit_ctrl(), the way of calculating the report length doesn't
> take into account that report->size can be zero. When running the
> syzkaller reproducer, a report of size 0 causes hid_submit_ctrl) to
> calculate transfer_buffer_length as 16384. When this urb is passed to
> the usb core layer, KMSAN reports an info leak of 16384 bytes.
> 
> To fix this, first modify hid_report_len() to account for the zero
> report size case by using DIV_ROUND_UP for the division. Then, call it
> from hid_submit_ctrl().
> 
> Reported-by: syzbot+7c2bb71996f95a82524c@syzkaller.appspotmail.com
> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>

Benjamin, could you please run this one through your regression testing 
machinery before we send it upstream?

Thanks,

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH] usbhid: fix info leak in hid_submit_ctrl

[Benjamin Tissoires]

On Wed, May 5, 2021 at 2:42 PM Jiri Kosina <jikos@kernel.org> wrote:
>
> On Sun, 25 Apr 2021, Anirudh Rayabharam wrote:
>
> > In hid_submit_ctrl(), the way of calculating the report length doesn't
> > take into account that report->size can be zero. When running the
> > syzkaller reproducer, a report of size 0 causes hid_submit_ctrl) to
> > calculate transfer_buffer_length as 16384. When this urb is passed to
> > the usb core layer, KMSAN reports an info leak of 16384 bytes.
> >
> > To fix this, first modify hid_report_len() to account for the zero
> > report size case by using DIV_ROUND_UP for the division. Then, call it
> > from hid_submit_ctrl().
> >
> > Reported-by: syzbot+7c2bb71996f95a82524c@syzkaller.appspotmail.com
> > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
>
> Benjamin, could you please run this one through your regression testing
> machinery before we send it upstream?
>

I don't have a reproducer like syzbot has for the exact bug here, as I
am relying on one real USB device to check if usbhid is not too
broken.
However, the test suite should catch if there is an error implied by
the hid_report_len() change.

Anyway, I manually started the job and will report when it is done.

Cheers,
Benjamin

Re: [PATCH] usbhid: fix info leak in hid_submit_ctrl

[Jiri Kosina]

On Wed, 5 May 2021, Benjamin Tissoires wrote:

> I don't have a reproducer like syzbot has for the exact bug here, as I 
> am relying on one real USB device to check if usbhid is not too broken. 
> However, the test suite should catch if there is an error implied by the 
> hid_report_len() change.

Yes, that was exactly what I wanted to check, sorry for not being verbose 
enough :)

> Anyway, I manually started the job and will report when it is done.

Thanks,

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH] usbhid: fix info leak in hid_submit_ctrl

[Benjamin Tissoires]

On Wed, May 5, 2021 at 3:28 PM Jiri Kosina <jikos@kernel.org> wrote:
>
> On Wed, 5 May 2021, Benjamin Tissoires wrote:
>
> > I don't have a reproducer like syzbot has for the exact bug here, as I
> > am relying on one real USB device to check if usbhid is not too broken.
> > However, the test suite should catch if there is an error implied by the
> > hid_report_len() change.
>
> Yes, that was exactly what I wanted to check, sorry for not being verbose
> enough :)
>
> > Anyway, I manually started the job and will report when it is done.
>

Heh, no problems.

"Job succeeded" \o/

Given that you are on a spree:
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Cheers,
Benjamin

Re: [PATCH] usbhid: fix info leak in hid_submit_ctrl

[Jiri Kosina]

On Wed, 5 May 2021, Benjamin Tissoires wrote:

> > > I don't have a reproducer like syzbot has for the exact bug here, as I
> > > am relying on one real USB device to check if usbhid is not too broken.
> > > However, the test suite should catch if there is an error implied by the
> > > hid_report_len() change.
> >
> > Yes, that was exactly what I wanted to check, sorry for not being verbose
> > enough :)
> >
> > > Anyway, I manually started the job and will report when it is done.
> >
> 
> Heh, no problems.
> 
> "Job succeeded" \o/
> 
> Given that you are on a spree:

:-)

> Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Applied to for-5.13/upstream-fixes. Thanks,

-- 
Jiri Kosina
SUSE Labs