This is a note to let you know that I've just added the patch titled KVM: PPC: Book3S: Fix race and leak in kvm_vm_ioctl_create_spapr_tce() to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-ppc-book3s-fix-race-and-leak-in-kvm_vm_ioctl_create_spapr_tce.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From paulus@xxxxxxxxxx Mon Oct 2 11:15:01 2017 From: Paul Mackerras <paulus@xxxxxxxxxx> Date: Tue, 12 Sep 2017 15:41:49 +1000 Subject: KVM: PPC: Book3S: Fix race and leak in kvm_vm_ioctl_create_spapr_tce() To: stable@xxxxxxxxxxxxxxx Message-ID: <20170912054149.3vrf3mcbtp4jodr6@xxxxxxxxxxxxxxxxxx> Content-Disposition: inline From: Paul Mackerras <paulus@xxxxxxxxxx> commit 47c5310a8dbe7c2cb9f0083daa43ceed76c257fa upstream, with part of commit edd03602d97236e8fea13cd76886c576186aa307 folded in. Nixiaoming pointed out that there is a memory leak in kvm_vm_ioctl_create_spapr_tce() if the call to anon_inode_getfd() fails; the memory allocated for the kvmppc_spapr_tce_table struct is not freed, and nor are the pages allocated for the iommu tables. In addition, we have already incremented the process's count of locked memory pages, and this doesn't get restored on error. David Hildenbrand pointed out that there is a race in that the function checks early on that there is not already an entry in the stt->iommu_tables list with the same LIOBN, but an entry with the same LIOBN could get added between then and when the new entry is added to the list. This fixes all three problems. To simplify things, we now call anon_inode_getfd() before placing the new entry in the list. The check for an existing entry is done while holding the kvm->lock mutex, immediately before adding the new entry to the list. Finally, on failure we now call kvmppc_account_memlimit to decrement the process's count of locked memory pages. [paulus@xxxxxxxxxx - folded in that part of edd03602d972 ("KVM: PPC: Book3S HV: Protect updates to spapr_tce_tables list", 2017-08-28) which restructured the code that 47c5310a8dbe modified, to avoid a build failure caused by the absence of put_unused_fd().] Fixes: 54738c097163 ("KVM: PPC: Accelerate H_PUT_TCE by implementing it in real mode") Fixes: f8626985c7c2 ("KVM: PPC: Account TCE-containing pages in locked_vm") Reported-by: Nixiaoming <nixiaoming@xxxxxxxxxx> Reported-by: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/kvm/book3s_64_vio.c | 56 ++++++++++++++++++++++----------------- 1 file changed, 32 insertions(+), 24 deletions(-) --- a/arch/powerpc/kvm/book3s_64_vio.c +++ b/arch/powerpc/kvm/book3s_64_vio.c @@ -150,6 +150,7 @@ long kvm_vm_ioctl_create_spapr_tce(struc struct kvm_create_spapr_tce_64 *args) { struct kvmppc_spapr_tce_table *stt = NULL; + struct kvmppc_spapr_tce_table *siter; unsigned long npages, size; int ret = -ENOMEM; int i; @@ -157,24 +158,16 @@ long kvm_vm_ioctl_create_spapr_tce(struc if (!args->size) return -EINVAL; - /* Check this LIOBN hasn't been previously allocated */ - list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list) { - if (stt->liobn == args->liobn) - return -EBUSY; - } - size = args->size; npages = kvmppc_tce_pages(size); ret = kvmppc_account_memlimit(kvmppc_stt_pages(npages), true); - if (ret) { - stt = NULL; - goto fail; - } + if (ret) + return ret; stt = kzalloc(sizeof(*stt) + npages * sizeof(struct page *), GFP_KERNEL); if (!stt) - goto fail; + goto fail_acct; stt->liobn = args->liobn; stt->page_shift = args->page_shift; @@ -188,24 +181,39 @@ long kvm_vm_ioctl_create_spapr_tce(struc goto fail; } - kvm_get_kvm(kvm); - mutex_lock(&kvm->lock); - list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables); - mutex_unlock(&kvm->lock); + /* Check this LIOBN hasn't been previously allocated */ + ret = 0; + list_for_each_entry(siter, &kvm->arch.spapr_tce_tables, list) { + if (siter->liobn == args->liobn) { + ret = -EBUSY; + break; + } + } + + if (!ret) + ret = anon_inode_getfd("kvm-spapr-tce", &kvm_spapr_tce_fops, + stt, O_RDWR | O_CLOEXEC); + + if (ret >= 0) { + list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables); + kvm_get_kvm(kvm); + } - return anon_inode_getfd("kvm-spapr-tce", &kvm_spapr_tce_fops, - stt, O_RDWR | O_CLOEXEC); + mutex_unlock(&kvm->lock); -fail: - if (stt) { - for (i = 0; i < npages; i++) - if (stt->pages[i]) - __free_page(stt->pages[i]); + if (ret >= 0) + return ret; - kfree(stt); - } + fail: + for (i = 0; i < npages; i++) + if (stt->pages[i]) + __free_page(stt->pages[i]); + + kfree(stt); + fail_acct: + kvmppc_account_memlimit(kvmppc_stt_pages(npages), false); return ret; } Patches currently in stable-queue which might be from paulus@xxxxxxxxxx are queue-4.9/kvm-ppc-book3s-fix-race-and-leak-in-kvm_vm_ioctl_create_spapr_tce.patch queue-4.9/kvm-ppc-book3s-hv-protect-updates-to-spapr_tce_tables-list.patch