Re: [libvirt] [PATCH 3/7] qemu: Remove possibility of NULL dereference

On Mon, Oct 10, 2016 at 11:42:14 -0400, John Ferlan wrote: > If qemubinCaps is NULL, then calling virQEMUCapsGetMachineTypesCaps and ^^^^^ This symbol name refers to the name in the caller. The function uses a different name. > dereferencing to get the nmachineTypes will cause a core. Rework the code It will cause a crash, not a core. A core dump is caused by the crash and can be turned off.

> slightly to avoid the issue and return immediately if !qemubinCaps or > !nmachineTypes > > Signed-off-by: John Ferlan <jferlan(a)redhat.com&gt; > --- > src/qemu/qemu_capabilities.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c > index da8f3d1..ee3e50f 100644 > --- a/src/qemu/qemu_capabilities.c > +++ b/src/qemu/qemu_capabilities.c > @@ -2405,10 +2405,13 @@ int virQEMUCapsGetMachineTypesCaps(virQEMUCapsPtr qemuCaps, > size_t i; > > *machines = NULL; > + *nmachines = 0; > + > + if (!qemuCaps || !qemuCaps->nmachineTypes) > + return 0; > *nmachines = qemuCaps->nmachineTypes; > > - if (*nmachines && > - VIR_ALLOC_N(*machines, qemuCaps->nmachineTypes) < 0) > + if (VIR_ALLOC_N(*machines, qemuCaps->nmachineTypes) < 0) > goto error; This is a false positive, the caller checks that 'binary' is set and does not call this function at all. Coverity probably doesn't see it as it depends on the state of 'binary' rather than 'qemubinCaps' in the caller.