Re: [libvirt] [PATCH] libvirt.c: don't let a NULL "cpumaps" argument provoke a NULL-deref

On Mon, Dec 14, 2009 at 05:18:54PM +0100, Jim Meyering wrote: > > > >From 94923b161a9d066146271bb533b78ab7877e4501 Mon Sep 17 00:00:00 2001 > From: Jim Meyering <meyering(a)redhat.com&gt; > Date: Mon, 14 Dec 2009 17:17:53 +0100 > Subject: [PATCH] libvirt.c: don't let a NULL "cpumaps" argument provoke a NULL-deref > > * src/libvirt.c (virDomainGetVcpus): Update spec to say that maplen > is ignored when "cpumaps" is NULL. > Set maplen to 0 in that case. > --- > src/libvirt.c | 7 +++++++ > 1 files changed, 7 insertions(+), 0 deletions(-) > > diff --git a/src/libvirt.c b/src/libvirt.c > index 008e322..4325aa4 100644 > --- a/src/libvirt.c > +++ b/src/libvirt.c > @@ -4753,6 +4753,7 @@ error: > * virDomainPinVcpu() API. > * @maplen: number of bytes in one cpumap, from 1 up to size of CPU map in > * underlying virtualization system (Xen...). > + * Ignored when cpumaps is NULL. > * > * Extract information about virtual CPUs of domain, store it in info array > * and also in cpumaps if this pointer isn't NULL. > @@ -4776,6 +4777,12 @@ virDomainGetVcpus(virDomainPtr domain, virVcpuInfoPtr info, int maxinfo, > virLibDomainError(domain, VIR_ERR_INVALID_ARG, __FUNCTION__); > goto error; > } > + > + /* Ensure that domainGetVcpus (aka remoteDomainGetVcpus) does not > + try to memcpy anything into a NULL pointer. */ > + if (cpumaps == NULL) > + maplen = 0; > + > if (cpumaps != NULL && maplen < 1) { > virLibDomainError(domain, VIR_ERR_INVALID_ARG, __FUNCTION__); > goto error; > -- I wonder if it might be better to return an error in that case. Passing a NULL cpumaps, and non-zero maplen seems like a real application bug we should complain about if (cpumaps == NULL && maplen != 0) ....error...