Re: [PATCH mellanox-tree] net/mlx5: prevent an integer underflow in mlx5_perout_configure()

On Mon, Mar 01, 2021 at 12:12:34PM +0200, Eran Ben Elisha wrote:

On 2/19/2021 11:57 AM, Dan Carpenter wrote:

quoted

The value of "sec" comes from the user.  Negative values will lead to
shift wrapping inside the perout_conf_real_time() function and triggger
a UBSan warning.

Add a check and return -EINVAL to prevent that from happening.

Fixes: 432119de33d9 ("net/mlx5: Add cyc2time HW translation mode support")
Signed-off-by: Dan Carpenter <redacted>
---
Saeed, I think this goes through your git tree and you will send a pull
request to the networking?

 From static analysis.  Not tested.

  drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
index b0e129d0f6d8..286824ca62b5 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c

@@ -516,7 +516,7 @@ static int mlx5_perout_configure(struct ptp_clock_info *ptp,
  		nsec = rq->perout.start.nsec;
  		sec = rq->perout.start.sec;
-		if (rt_mode && sec > U32_MAX)

This if clause was set to reject perout time start sec bigger than U32_MAX,
as rt mode specifically doesn't support it.

A user negative values protection should be generic for all netdev drivers,
inside the caller ioctl func, and not part of any driver code.

I'm not a networking expert...  :/  It's easier for me to see that this
code will trigger a syzbot splat vs saying that there is no valid use
case for negative seconds any driver.

What you're saying sounds reasonable enough to me, but I don't know
enough about networking to comment one way or the other.  Maybe the
other drivers have a use for negative seconds?

regards,
dan carpenter

quoted

+		if (rt_mode && (sec < 0 || sec > U32_MAX))
  			return -EINVAL;
  		time_stamp = rt_mode ? perout_conf_real_time(sec, nsec) :