From b4e51229d8a1e499fe65153766437152cca42053 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Fri, 3 Feb 2012 00:45:02 +0000 Subject: [PATCH] KVM: PPC: Book3S HV: Fix kvm_alloc_linear in case where no linears exist In kvm_alloc_linear we were using and deferencing ri after the list_for_each_entry had come to the end of the list. In that situation, ri is not really defined and probably points to the list head. This will happen every time if the free_linears list is empty, for instance. This led to a NULL pointer dereference crash in memset on POWER7 while trying to allocate an HPT in the case where no HPTs were preallocated. This fixes it by using a separate variable for the return value from the loop iterator. Signed-off-by: Paul Mackerras Signed-off-by: Alexander Graf Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s_hv_builtin.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c index bed1279aa6a8..e1b60f56f2a1 100644 --- a/arch/powerpc/kvm/book3s_hv_builtin.c +++ b/arch/powerpc/kvm/book3s_hv_builtin.c @@ -173,9 +173,9 @@ static void __init kvm_linear_init_one(ulong size, int count, int type) static struct kvmppc_linear_info *kvm_alloc_linear(int type) { - struct kvmppc_linear_info *ri; + struct kvmppc_linear_info *ri, *ret; - ri = NULL; + ret = NULL; spin_lock(&linear_lock); list_for_each_entry(ri, &free_linears, list) { if (ri->type != type) @@ -183,11 +183,12 @@ static struct kvmppc_linear_info *kvm_alloc_linear(int type) list_del(&ri->list); atomic_inc(&ri->use_count); + memset(ri->base_virt, 0, ri->npages << PAGE_SHIFT); + ret = ri; break; } spin_unlock(&linear_lock); - memset(ri->base_virt, 0, ri->npages << PAGE_SHIFT); - return ri; + return ret; } static void kvm_release_linear(struct kvmppc_linear_info *ri) -- 2.30.2