[ovs-dev] [PATCH 08/11] ovn-sbctl: Fix possible null pointer to qsort.

[Ben Pfaff]

I'd recommend just something like "if (n_flows) { qsort(...); }".

On Mon, Oct 30, 2017 at 12:05:55PM -0700, William Tu wrote:
> Hi Mark,
> Thanks for the review. I will fix it and resubmit v2.
> William
> 
> On Mon, Oct 30, 2017 at 8:12 AM, Mark Michelson <mmichels at redhat.com> wrote:
> > This is not the proper solution. If you start ovn-northd and do not add any
> > logical switches or routers, then there will be no logical flows created.
> > Currently, if you run `ovs-sbctl lflow-list` in this circumstance, it lists
> > nothing and exits cleanly. With this change, the command hits the assertion
> > and crashes.
> > it's not an erroneous case to have no logical flows to sort. I think the
> > proper thing to do in this case is to check the value of n_flows after the
> > loop that populates lflows. If it is 0, then close the vconn and exit the
> > function early.
> >
> > On Sat, Oct 28, 2017 at 12:37 PM William Tu <u9012063 at gmail.com> wrote:
> >>
> >> Clang reports possible null pointer 'lflows' passed to qsort.
> >> This is due to the checker unable to make sure whether 'lflows'
> >> gets malloc or not in the previous loop.  Thus, fix it by adding
> >> ovs_assert to pass clang checker.
> >>
> >> Signed-off-by: William Tu <u9012063 at gmail.com>
> >> ---
> >>  ovn/utilities/ovn-sbctl.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/ovn/utilities/ovn-sbctl.c b/ovn/utilities/ovn-sbctl.c
> >> index 7af5863b08fc..b1f106002842 100644
> >> --- a/ovn/utilities/ovn-sbctl.c
> >> +++ b/ovn/utilities/ovn-sbctl.c
> >> @@ -860,6 +860,7 @@ cmd_lflow_list(struct ctl_context *ctx)
> >>          lflows[n_flows] = lflow;
> >>          n_flows++;
> >>      }
> >> +    ovs_assert(lflows);
> >>      qsort(lflows, n_flows, sizeof *lflows, lflow_cmp);
> >>
> >>      bool print_uuid = shash_find(&ctx->options, "--uuid") != NULL;
> >> --
> >> 2.7.4
> >>
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