Messages in this thread | | | From | Petr Machata <> | Subject | Re: mlxsw: spectrum: PTP: Support timestamping on Spectrum-1 - potential null ptr dereference | Date | Tue, 2 Jul 2019 15:51:17 +0000 |
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Colin Ian King <colin.king@canonical.com> writes:
> Hi, > > Static analysis with Coverity on today's linux-next has found a > potential null pointer dereference bug with the following commit: > > commit d92e4e6e33c8b19635be70fb8935b627d2e4f8fe > Author: Petr Machata <petrm@mellanox.com> > Date: Sun Jun 30 09:04:56 2019 +0300 > > mlxsw: spectrum: PTP: Support timestamping on Spectrum-1 > > > In function: mlxsw_sp1_ptp_packet_finish the offending code is as follows: > > /* Between capturing the packet and finishing it, there is a > window of > * opportunity for the originating port to go away (e.g. due to a > * split). Also make sure the SKB device reference is still valid. > */ > mlxsw_sp_port = mlxsw_sp->ports[local_port]; > if (!mlxsw_sp_port && (!skb->dev || skb->dev == mlxsw_sp_port->dev)) { > dev_kfree_skb_any(skb); > return; > } > > If mlxsw_sp_port is null and skb->dev is not-null then the comparison > "skb->dev == mlxsw_sp_port->dev" ends up with a null pointer dereference. > > I think the if statement should be: > > if (mlxsw_sp_port && (!skb->dev || skb->dev == mlxsw_sp_port->dev)) > > ..but I'm not 100% sure as I may be missing something a bit more subtle > here.
Yes, that line is wrong. It's missing a pair of parens, it should be:
if (!(mlxsw_sp_port && (!skb->dev || skb->dev == mlxsw_sp_port->dev))) {
I.e. I need a port && I need the skb->dev to still refer to that port (or else be NULL). If that doesn't hold, bail out.
Thanks for the report, I'll spin a fix!
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