[libvirt] [PATCH] x86Decode: avoid NULL-dereference upon questionable input

Clang warned about the potential NULL-dereference via the STREQ/strcmp below. models[i] could be NULL. Even "models" could be NULL, and the "allowed = ..." test makes that appear to be deliberately allowed. The change below is the least invasive and cleanest I could come up with, assuming there is no need to diagnose (e.g., by returning -1) the condition of a NULL models[i] pointer. From: Jim Meyering <meyering(a)redhat.com&gt; Date: Sun, 28 Feb 2010 13:34:06 +0100 Subject: [PATCH] x86Decode: avoid NULL-dereference upon questionable input * src/cpu/cpu_x86.c (x86Decode): Don't dereference NULL when passed a NULL "models" pointer, or when passed a nonzero "nmodels" value and a corresponding NULL models[i]. --- src/cpu/cpu_x86.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c index 2194c32..b263629 100644 --- a/src/cpu/cpu_x86.c +++ b/src/cpu/cpu_x86.c @@ -957,89 +957,89 @@ x86Compare(virCPUDefPtr host, virCPUDefPtr cpu) { return x86Compute(host, cpu, NULL); } static virCPUCompareResult x86GuestData(virCPUDefPtr host, virCPUDefPtr guest, union cpuData **data) { return x86Compute(host, guest, data); } static int x86Decode(virCPUDefPtr cpu, const union cpuData *data, const char **models, unsigned int nmodels) { int ret = -1; struct x86_map *map; const struct x86_model *candidate; virCPUDefPtr cpuCandidate; virCPUDefPtr cpuModel = NULL; struct cpuX86cpuid *cpuid; int i; if (data == NULL || (map = x86LoadMap()) == NULL) return -1; candidate = map->models; while (candidate != NULL) { bool allowed = (models == NULL); for (i = 0; i < candidate->ncpuid; i++) { cpuid = x86DataCpuid(data, candidate->cpuid[i].function); if (cpuid == NULL || !x86cpuidMatchMasked(cpuid, candidate->cpuid + i)) goto next; } for (i = 0; i < nmodels; i++) { - if (STREQ(models[i], candidate->name)) { + if (models && models[i] && STREQ(models[i], candidate->name)) { allowed = true; break; } } if (!allowed) { VIR_DEBUG("CPU model %s not allowed by hypervisor; ignoring", candidate->name); goto next; } if (!(cpuCandidate = x86DataToCPU(data, candidate, map))) goto out; if (cpuModel == NULL || cpuModel->nfeatures > cpuCandidate->nfeatures) { virCPUDefFree(cpuModel); cpuModel = cpuCandidate; } else virCPUDefFree(cpuCandidate); next: candidate = candidate->next; } if (cpuModel == NULL) { virCPUReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("Cannot find suitable CPU model for given data")); goto out; } cpu->model = cpuModel->model; cpu->nfeatures = cpuModel->nfeatures; cpu->features = cpuModel->features; VIR_FREE(cpuModel); ret = 0; out: x86MapFree(map); virCPUDefFree(cpuModel); return ret; } -- 1.7.0.1.414.g89213d