From: Sean Christopherson Date: Fri, 13 Mar 2026 00:32:58 +0000 (-0700) Subject: KVM: SEV: Drop WARN on large size for KVM_MEMORY_ENCRYPT_REG_REGION X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8acffeef5ef720c35e513e322ab08e32683f32f2;p=thirdparty%2Fkernel%2Flinux.git KVM: SEV: Drop WARN on large size for KVM_MEMORY_ENCRYPT_REG_REGION Drop the WARN in sev_pin_memory() on npages overflowing an int, as the WARN is comically trivially to trigger from userspace, e.g. by doing: struct kvm_enc_region range = { .addr = 0, .size = -1ul, }; __vm_ioctl(vm, KVM_MEMORY_ENCRYPT_REG_REGION, &range); Note, the checks in sev_mem_enc_register_region() that presumably exist to verify the incoming address+size are completely worthless, as both "addr" and "size" are u64s and SEV is 64-bit only, i.e. they _can't_ be greater than ULONG_MAX. That wart will be cleaned up in the near future. if (range->addr > ULONG_MAX || range->size > ULONG_MAX) return -EINVAL; Opportunistically add a comment to explain why the code calculates the number of pages the "hard" way, e.g. instead of just shifting @ulen. Fixes: 78824fabc72e ("KVM: SVM: fix svn_pin_memory()'s use of get_user_pages_fast()") Cc: stable@vger.kernel.org Reviewed-by: Liam Merwick Tested-by: Liam Merwick Link: https://patch.msgid.link/20260313003302.3136111-2-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 77ebc166abfd1..2c216726718d9 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -690,10 +690,16 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr, if (ulen == 0 || uaddr + ulen < uaddr) return ERR_PTR(-EINVAL); - /* Calculate number of pages. */ + /* + * Calculate the number of pages that need to be pinned to cover the + * entire range. Note! This isn't simply ulen >> PAGE_SHIFT, as KVM + * doesn't require the incoming address+size to be page aligned! + */ first = (uaddr & PAGE_MASK) >> PAGE_SHIFT; last = ((uaddr + ulen - 1) & PAGE_MASK) >> PAGE_SHIFT; npages = (last - first + 1); + if (npages > INT_MAX) + return ERR_PTR(-EINVAL); locked = sev->pages_locked + npages; lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; @@ -702,9 +708,6 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr, return ERR_PTR(-ENOMEM); } - if (WARN_ON_ONCE(npages > INT_MAX)) - return ERR_PTR(-EINVAL); - /* Avoid using vmalloc for smaller buffers. */ size = npages * sizeof(struct page *); if (size > PAGE_SIZE)