KMSAN: uninit-value in digitv_rc_query

KMSAN: uninit-value in digitv_rc_query

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    1e76a3e5 kmsan: replace __GFP_NO_KMSAN_SHADOW with kmsan_i..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=16860a63600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f03c659d0830ab8d
dashboard link: https://syzkaller.appspot.com/bug?extid=6bf9606ee955b646c0e1
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12c1101b600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15db3cfd600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com

dvb-usb: schedule remote query interval to 1000 msecs.
dvb-usb: Nebula Electronics uDigiTV DVB-T USB2.0) successfully initialized  
and connected.
dvb-usb: bulk message failed: -22 (7/0)
dvb-usb: bulk message failed: -22 (7/0)
dvb-usb: bulk message failed: -22 (7/-30591)
dvb-usb: bulk message failed: -22 (7/0)
=====================================================
BUG: KMSAN: uninit-value in legacy_dvb_usb_read_remote_control+0x106/0x790  
drivers/media/usb/dvb-usb/dvb-usb-remote.c:123
CPU: 1 PID: 3844 Comm: kworker/1:2 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events legacy_dvb_usb_read_remote_control
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x191/0x1f0 lib/dump_stack.c:113
  kmsan_report+0x13a/0x2b0 mm/kmsan/kmsan_report.c:108
  __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
  digitv_rc_query+0x76a/0x890 drivers/media/usb/dvb-usb/digitv.c:259
  legacy_dvb_usb_read_remote_control+0x106/0x790  
drivers/media/usb/dvb-usb/dvb-usb-remote.c:123
  process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
  worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
  kthread+0x4b5/0x4f0 kernel/kthread.c:256
  ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Local variable description: ----key@digitv_rc_query
Variable was created at:
  digitv_rc_query+0x78/0x890 drivers/media/usb/dvb-usb/digitv.c:234
  legacy_dvb_usb_read_remote_control+0x106/0x790  
drivers/media/usb/dvb-usb/dvb-usb-remote.c:123
=====================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 3844 Comm: kworker/1:2 Tainted: G    B             5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events legacy_dvb_usb_read_remote_control
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x191/0x1f0 lib/dump_stack.c:113
  panic+0x3c9/0xc1e kernel/panic.c:219
  kmsan_report+0x2a2/0x2b0 mm/kmsan/kmsan_report.c:131
  __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
  digitv_rc_query+0x76a/0x890 drivers/media/usb/dvb-usb/digitv.c:259
  legacy_dvb_usb_read_remote_control+0x106/0x790  
drivers/media/usb/dvb-usb/dvb-usb-remote.c:123
  process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
  worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
  kthread+0x4b5/0x4f0 kernel/kthread.c:256
  ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[PATCH] media: dvb: check return value digitv_ctrl_msg

[Phong Tran]

For fixing syzbot "KMSAN: uninit-value in digitv_rc_query"

In scenario testing for syzbot, failure reading from
digitv_ctrl_msg() [1].

Eg:
[   91.846657][ T3844] dvb-usb: bulk message failed: -22 (7/0)

digitv_rc_query() always return 0. But in this case a wrong thing happens.

Reported-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
Tested-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com

[1]: https://syzkaller.appspot.com/text?tag=CrashLog&x=16860a63600000
[2]: https://groups.google.com/d/msg/syzkaller-bugs/-TXIJAZ0J9Q/T4PEUQoeAQAJ

Signed-off-by: Phong Tran <tranmanphong@gmail.com>
---
 drivers/media/usb/dvb-usb/digitv.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/digitv.c b/drivers/media/usb/dvb-usb/digitv.c
index dd5bb230cec1..61bc8945e6b9 100644
--- a/drivers/media/usb/dvb-usb/digitv.c
+++ b/drivers/media/usb/dvb-usb/digitv.c
@@ -231,17 +231,21 @@ static struct rc_map_table rc_map_digitv_table[] = {
 static int digitv_rc_query(struct dvb_usb_device *d, u32 *event, int *state)
 {
 	int i;
-	u8 key[5];
+	u8 key[5] = { 0 };
 	u8 b[4] = { 0 };
+	int ret;
 
 	*event = 0;
 	*state = REMOTE_NO_KEY_PRESSED;
 
-	digitv_ctrl_msg(d,USB_READ_REMOTE,0,NULL,0,&key[1],4);
-
+	ret = digitv_ctrl_msg(d, USB_READ_REMOTE, 0, NULL, 0, &key[1], 4);
+	if (ret < 0)
+		return ret;
 	/* Tell the device we've read the remote. Not sure how necessary
 	   this is, but the Nebula SDK does it. */
-	digitv_ctrl_msg(d,USB_WRITE_REMOTE,0,b,4,NULL,0);
+	ret = digitv_ctrl_msg(d, USB_WRITE_REMOTE, 0, b, 4, NULL, 0);
+	if (ret < 0)
+		return ret;
 
 	/* if something is inside the buffer, simulate key press */
 	if (key[1] != 0)
-- 
2.20.1

Re: [PATCH] media: dvb: check return value digitv_ctrl_msg

[Sean Young]

Hello,

On Tue, Dec 03, 2019 at 07:41:38AM +0700, Phong Tran wrote:
> For fixing syzbot "KMSAN: uninit-value in digitv_rc_query"
> 
> In scenario testing for syzbot, failure reading from
> digitv_ctrl_msg() [1].
> 
> Eg:
> [   91.846657][ T3844] dvb-usb: bulk message failed: -22 (7/0)
> 
> digitv_rc_query() always return 0. But in this case a wrong thing happens.
> 
> Reported-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
> Tested-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com

A fix for this was already merged I'm afraid, see commit eecc70d22ae5
("media: digitv: don't continue if remote control state can't be read").

> [1]: https://syzkaller.appspot.com/text?tag=CrashLog&x=16860a63600000
> [2]: https://groups.google.com/d/msg/syzkaller-bugs/-TXIJAZ0J9Q/T4PEUQoeAQAJ
> 
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
>  drivers/media/usb/dvb-usb/digitv.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb/digitv.c b/drivers/media/usb/dvb-usb/digitv.c
> index dd5bb230cec1..61bc8945e6b9 100644
> --- a/drivers/media/usb/dvb-usb/digitv.c
> +++ b/drivers/media/usb/dvb-usb/digitv.c
> @@ -231,17 +231,21 @@ static struct rc_map_table rc_map_digitv_table[] = {
>  static int digitv_rc_query(struct dvb_usb_device *d, u32 *event, int *state)
>  {
>  	int i;
> -	u8 key[5];
> +	u8 key[5] = { 0 };

The merged commit does not change this line. Why was this changed?

Thanks

Sean

>  	u8 b[4] = { 0 };
> +	int ret;
>  
>  	*event = 0;
>  	*state = REMOTE_NO_KEY_PRESSED;
>  
> -	digitv_ctrl_msg(d,USB_READ_REMOTE,0,NULL,0,&key[1],4);
> -
> +	ret = digitv_ctrl_msg(d, USB_READ_REMOTE, 0, NULL, 0, &key[1], 4);
> +	if (ret < 0)
> +		return ret;
>  	/* Tell the device we've read the remote. Not sure how necessary
>  	   this is, but the Nebula SDK does it. */
> -	digitv_ctrl_msg(d,USB_WRITE_REMOTE,0,b,4,NULL,0);
> +	ret = digitv_ctrl_msg(d, USB_WRITE_REMOTE, 0, b, 4, NULL, 0);
> +	if (ret < 0)
> +		return ret;
>  
>  	/* if something is inside the buffer, simulate key press */
>  	if (key[1] != 0)
> -- 
> 2.20.1

Re: [PATCH] media: dvb: check return value digitv_ctrl_msg

[Dan Carpenter]

On Wed, Jan 15, 2020 at 05:32:26PM +0000, Sean Young wrote:
> Hello,
> 
> On Tue, Dec 03, 2019 at 07:41:38AM +0700, Phong Tran wrote:
> > For fixing syzbot "KMSAN: uninit-value in digitv_rc_query"
> > 
> > In scenario testing for syzbot, failure reading from
> > digitv_ctrl_msg() [1].
> > 
> > Eg:
> > [   91.846657][ T3844] dvb-usb: bulk message failed: -22 (7/0)
> > 
> > digitv_rc_query() always return 0. But in this case a wrong thing happens.
> > 
> > Reported-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
> > Tested-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
> 
> A fix for this was already merged I'm afraid, see commit eecc70d22ae5
> ("media: digitv: don't continue if remote control state can't be read").
> 
> > [1]: https://syzkaller.appspot.com/text?tag=CrashLog&x=16860a63600000
> > [2]: https://groups.google.com/d/msg/syzkaller-bugs/-TXIJAZ0J9Q/T4PEUQoeAQAJ
> > 
> > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> > ---
> >  drivers/media/usb/dvb-usb/digitv.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/media/usb/dvb-usb/digitv.c b/drivers/media/usb/dvb-usb/digitv.c
> > index dd5bb230cec1..61bc8945e6b9 100644
> > --- a/drivers/media/usb/dvb-usb/digitv.c
> > +++ b/drivers/media/usb/dvb-usb/digitv.c
> > @@ -231,17 +231,21 @@ static struct rc_map_table rc_map_digitv_table[] = {
> >  static int digitv_rc_query(struct dvb_usb_device *d, u32 *event, int *state)
> >  {
> >  	int i;
> > -	u8 key[5];
> > +	u8 key[5] = { 0 };
> 
> The merged commit does not change this line. Why was this changed?
> 

It would fix the problem that key[0] is never initialized...  But the
correct fix is to make key 4 elements long and delete key[0].

regards,
dan carpenter

Re: [PATCH] media: dvb: check return value digitv_ctrl_msg

[Dan Carpenter]

On Wed, Jan 15, 2020 at 09:01:17PM +0300, Dan Carpenter wrote:
> On Wed, Jan 15, 2020 at 05:32:26PM +0000, Sean Young wrote:
> > Hello,
> > 
> > On Tue, Dec 03, 2019 at 07:41:38AM +0700, Phong Tran wrote:
> > > For fixing syzbot "KMSAN: uninit-value in digitv_rc_query"
> > > 
> > > In scenario testing for syzbot, failure reading from
> > > digitv_ctrl_msg() [1].
> > > 
> > > Eg:
> > > [   91.846657][ T3844] dvb-usb: bulk message failed: -22 (7/0)
> > > 
> > > digitv_rc_query() always return 0. But in this case a wrong thing happens.
> > > 
> > > Reported-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
> > > Tested-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
> > 
> > A fix for this was already merged I'm afraid, see commit eecc70d22ae5
> > ("media: digitv: don't continue if remote control state can't be read").
> > 
> > > [1]: https://syzkaller.appspot.com/text?tag=CrashLog&x=16860a63600000
> > > [2]: https://groups.google.com/d/msg/syzkaller-bugs/-TXIJAZ0J9Q/T4PEUQoeAQAJ
> > > 
> > > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> > > ---
> > >  drivers/media/usb/dvb-usb/digitv.c | 12 ++++++++----
> > >  1 file changed, 8 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/media/usb/dvb-usb/digitv.c b/drivers/media/usb/dvb-usb/digitv.c
> > > index dd5bb230cec1..61bc8945e6b9 100644
> > > --- a/drivers/media/usb/dvb-usb/digitv.c
> > > +++ b/drivers/media/usb/dvb-usb/digitv.c
> > > @@ -231,17 +231,21 @@ static struct rc_map_table rc_map_digitv_table[] = {
> > >  static int digitv_rc_query(struct dvb_usb_device *d, u32 *event, int *state)
> > >  {
> > >  	int i;
> > > -	u8 key[5];
> > > +	u8 key[5] = { 0 };
> > 
> > The merged commit does not change this line. Why was this changed?
> > 
> 
> It would fix the problem that key[0] is never initialized...  But the
> correct fix is to make key 4 elements long and delete key[0].

Phong,

Presumably you can fix this?  You will have to renumber key[1] to
key[0] and key[2] to key[1] etc...  Add a fixes tag.

Fixes: 774c0de4aed4 ("V4L/DVB (4616): [PATCH] Nebula DigiTV USB RC support")

Otherwise if you want I can send the patch.

regards,
dan carpenter