From: Alexey Kardashevskiy <aik@ozlabs.ru>
Date: Wed, 1 Sep 2021 08:45:12 +0000 (+1000)
Subject: KVM: PPC: Book3S: Suppress warnings when allocating too big memory slots
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=a0a4d7a23d18c2953d76d26dedf82a74a1943177;p=linux.git

KVM: PPC: Book3S: Suppress warnings when allocating too big memory slots

[ Upstream commit 511d25d6b789fffcb20a3eb71899cf974a31bd9d ]

The userspace can trigger "vmalloc size %lu allocation failure: exceeds
total pages" via the KVM_SET_USER_MEMORY_REGION ioctl.

This silences the warning by checking the limit before calling vzalloc()
and returns ENOMEM if failed.

This does not call underlying valloc helpers as __vmalloc_node() is only
exported when CONFIG_TEST_VMALLOC_MODULE and __vmalloc_node_range() is
not exported at all.

Spotted by syzkaller.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[mpe: Use 'size' for the variable rather than 'cb']
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210901084512.1658628-1-aik@ozlabs.ru
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 7b74fc0a986b8..94da0d25eb125 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4861,8 +4861,12 @@ static int kvmppc_core_prepare_memory_region_hv(struct kvm *kvm,
 	unsigned long npages = mem->memory_size >> PAGE_SHIFT;
 
 	if (change == KVM_MR_CREATE) {
-		slot->arch.rmap = vzalloc(array_size(npages,
-					  sizeof(*slot->arch.rmap)));
+		unsigned long size = array_size(npages, sizeof(*slot->arch.rmap));
+
+		if ((size >> PAGE_SHIFT) > totalram_pages())
+			return -ENOMEM;
+
+		slot->arch.rmap = vzalloc(size);
 		if (!slot->arch.rmap)
 			return -ENOMEM;
 	}