On Tue, Aug 23, 2022 at 06:43:26PM +0200, Peter Krempa wrote:
> On Tue, Aug 23, 2022 at 18:22:37 +0200, Erik Skultety wrote:
> > Coverity reports:
> > virNWFilterSnoopIPLeaseUpdate(virNWFilterSnoopIPLease *ipl,
> > time_t timeout)
> > {
> > if (timeout < ipl->timeout)
> > return; /* no take-backs */
> >
> > virNWFilterSnoopIPLeaseTimerDel(ipl);
> > >>> CID 396747: High impact quality (Y2K38_SAFETY)
> > >>> A "time_t" value is stored in an integer with too few bits
> > to accommodate it. The expression "timeout" is cast to
> > "unsigned int".
> > ipl->timeout = timeout;
> > virNWFilterSnoopIPLeaseTimerAdd(ipl);
> > }
> >
> > Given that it doesn't make sense for a timeout to be negative, let's
> > store it as unsigned long long and typecast all affected time_t
> > occurrences accordingly. Since the affected places only ever get the
> > current time which is not going to be negative (unless it's year 2038
> > and a 32bit architecture) we can safely cast them.
> >
> > Signed-off-by: Erik Skultety <eskultet@xxxxxxxxxx>
> > ---
> > src/nwfilter/nwfilter_dhcpsnoop.c | 12 +++++++-----
> > 1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/src/nwfilter/nwfilter_dhcpsnoop.c b/src/nwfilter/nwfilter_dhcpsnoop.c
> > index 18812c0b20..0977951be1 100644
> > --- a/src/nwfilter/nwfilter_dhcpsnoop.c
> > +++ b/src/nwfilter/nwfilter_dhcpsnoop.c
> > @@ -146,7 +146,7 @@ struct _virNWFilterSnoopIPLease {
> > virSocketAddr ipAddress;
> > virSocketAddr ipServer;
> > virNWFilterSnoopReq * snoopReq;
> > - unsigned int timeout;
> > + unsigned long long timeout;
>
> [1]
>
> > /* timer list */
> > virNWFilterSnoopIPLease *prev;
> > virNWFilterSnoopIPLease *next;
> > @@ -415,7 +415,8 @@ virNWFilterSnoopIPLeaseInstallRule(virNWFilterSnoopIPLease *ipl,
> > * virNWFilterSnoopIPLeaseUpdate - update the timeout on an IP lease
> > */
> > static void
> > -virNWFilterSnoopIPLeaseUpdate(virNWFilterSnoopIPLease *ipl, time_t timeout)
> > +virNWFilterSnoopIPLeaseUpdate(virNWFilterSnoopIPLease *ipl,
> > + unsigned long long timeout)
> > {
> > if (timeout < ipl->timeout)
> > return; /* no take-backs */
> > @@ -447,7 +448,7 @@ virNWFilterSnoopIPLeaseGetByIP(virNWFilterSnoopIPLease *start,
> > static unsigned int
> > virNWFilterSnoopReqLeaseTimerRun(virNWFilterSnoopReq *req)
> > {
> > - time_t now = time(0);
> > + unsigned long long now = time(0);
>
> This should also use NULL instead of 0.
>
> > bool is_last = false;
> >
> > /* protect req->start */
> > @@ -1580,7 +1581,8 @@ virNWFilterSnoopLeaseFileWrite(int lfd, const char *ifkey,
> > return -1;
> >
> > /* time intf ip dhcpserver */
> > - lbuf = g_strdup_printf("%u %s %s %s\n", ipl->timeout, ifkey, ipstr, dhcpstr);
> > + lbuf = g_strdup_printf("%llu %s %s %s\n",
> > + ipl->timeout, ifkey, ipstr, dhcpstr);
> > len = strlen(lbuf);
> >
> > if (safewrite(lfd, lbuf, len) != len) {
> > @@ -1737,7 +1739,7 @@ virNWFilterSnoopLeaseFileLoad(void)
> > }
> > ln++;
> > /* key len 54 = "VMUUID"+'-'+"MAC" */
> > - if (sscanf(line, "%u %54s %15s %15s", &ipl.timeout,
> > + if (sscanf(line, "%llu %54s %15s %15s", &ipl.timeout,
> > ifkey, ipstr, srvstr) < 4) {
> > virReportError(VIR_ERR_INTERNAL_ERROR,
> > _("virNWFilterSnoopLeaseFileLoad lease file "
>
> It feels to me that using a temporary unsigned long long variable to do
> the sscanf and store everything in a time_t [1] would look more
> appropriate as there shouldn't be a problem with time_t itself, right?
There actually is (and I neglected the fact in v1) - the C standard only
defines time_t as a signed type which can be either an integer type or even a
float, but nothing else. Since there isn't a type formatter for time_t,
compilers and coverity might complain in the future about signedness again (I'm
especially worried about scanf given its nature). Therefore I decided to go
with unsigned long long because it's always predictable and always 64bit. To me
storing the timeout as something else than time_t with enough bit space seems
like a better solution.
Erik
