Check for invalid hva address stored in data and return -EINVAL before calling into __kvm_gpc_activate(). Reported-by: syzbot+fd555292a1da3180fc82@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=fd555292a1da3180fc82 Tested-by: syzbot+fd555292a1da3180fc82@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Pei Li <peili.dev@xxxxxxxxx> --- Syzbot reports a warning message in __kvm_gpc_refresh(). This warning requires at least one of gpa and uhva to be valid. WARNING: CPU: 0 PID: 5090 at arch/x86/kvm/../../../virt/kvm/pfncache.c:259 __kvm_gpc_refresh+0xf17/0x1090 arch/x86/kvm/../../../virt/kvm/pfncache.c:259 We are calling it from kvm_gpc_activate_hva(). This function always calls __kvm_gpc_activate() with INVALID_GPA. Thus, uhva must be valid to disable this warning. This patch checks for invalid hva address and return -EINVAL before calling __kvm_gpc_activate(). syzbot has tested the proposed patch and the reproducer did not trigger any issue. Tested on: commit: afcd4813 Merge tag 'mm-hotfixes-stable-2024-06-26-17-2.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1427e301980000 kernel config: https://syzkaller.appspot.com/x/.config?x=e40800950091403a dashboard link: https://syzkaller.appspot.com/bug?extid=fd555292a1da3180fc82 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=13838f3e980000 Note: testing is done by a robot and is best-effort only. --- Changes in v2: - Adapted Sean's suggestion to check for valid address before calling into __kvm_gpc_activate(). - Link to v1: https://lore.kernel.org/r/20240625-bug5-v1-1-e072ed5fce85@xxxxxxxxx --- arch/x86/kvm/xen.c | 2 +- virt/kvm/pfncache.c | 3 +++ 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index f65b35a05d91..67bb4e89c399 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -741,7 +741,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) } else { void __user * hva = u64_to_user_ptr(data->u.shared_info.hva); - if (!PAGE_ALIGNED(hva) || !access_ok(hva, PAGE_SIZE)) { + if (!PAGE_ALIGNED(hva)) { r = -EINVAL; } else if (!hva) { kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache); diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index e3453e869e92..f0039efb9e1e 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -430,6 +430,9 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long uhva, unsigned long len) { + if (!access_ok((void __user *)uhva, len)) + return -EINVAL; + return __kvm_gpc_activate(gpc, INVALID_GPA, uhva, len); } --- base-commit: 2bfcfd584ff5ccc8bb7acde19b42570414bf880b change-id: 20240625-bug5-5d332b5e5161 Best regards, -- Pei Li <peili.dev@xxxxxxxxx>
