From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Graf Date: Thu, 15 Mar 2012 12:11:10 +0000 Subject: [PATCH 41/56] KVM: PPC: Book3S HV: Fix kvm_alloc_linear in case where no linears exist Message-Id: <1331813485-14722-42-git-send-email-agraf@suse.de> List-Id: References: <1331813485-14722-1-git-send-email-agraf@suse.de> In-Reply-To: <1331813485-14722-1-git-send-email-agraf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm-ppc@vger.kernel.org Cc: kvm@vger.kernel.org, Paul Mackerras From: Paul Mackerras 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 --- arch/powerpc/kvm/book3s_hv_builtin.c | 9 +++++---- 1 files changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c index bed1279..e1b60f5 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) -- 1.6.0.2