On Mon, 1 May 2017, Gustavo A. R. Silva wrote: > Hello everybody, > > While taking a look into Coverity ID 100828 I ran into the following > piece of code at drivers/usb/host/ehci-sched.c:1096: > > u32 addr; > int think_time; > int hs_transfers; > > addr = dev->ttport << 24; > if (!ehci_is_TDI(ehci) > || (dev->tt->hub != > ehci_to_hcd(ehci)->self.root_hub)) > addr |= dev->tt->hub->devnum << 16; > addr |= epnum << 8; > addr |= dev->devnum; > stream->ps.usecs = HS_USECS_ISO(maxp); > think_time = dev->tt ? dev->tt->think_time : 0; > > The issue here is that dev->tt is being dereferenced before null check. > > I was thinking on placing think_time = dev->tt ? dev->tt->think_time : > 0; just before the _if_ statement. But this doesn't address the > problem of dev->tt actually being NULL. > > While looking into the callers of the function containing this piece > of code (iso_stream_init()) my impression is that dev->tt is not NULL > at the time this function is called and, a very simple patch like the > following can be applied in order to avoid the Coverity issue: > > -think_time = dev->tt ? dev->tt->think_time : 0; > +think_time = dev->tt->think_time; > > But I can't tell for sure, so in case dev->tt is NULL, a good strategy > to properly update the _addr_ variable would be needed. > > What do you think? > > I would really appreciate any comment on this, > Thank you! You are right; udev->tt cannot ever be NULL when this section of code runs. The test should be removed. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
