Subject: [PATCH AUTOSEL 5.15 13/44] KVM: PPC: Book3S: Suppress warnings when allocating too big memory slots

From: Sasha Levin <[email-masked]>
Date: Mon, 17 Jan 2022 12:00:56 -0500

From: Alexey Kardashevskiy <[email-masked]>

[ 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 <[email-masked]>
[mpe: Use 'size' for the variable rather than 'cb']
Signed-off-by: Michael Ellerman <[email-masked]>
Link: https://lore.kernel.org/r/[email-masked]
Signed-off-by: Sasha Levin <[email-masked]>
---
 arch/powerpc/kvm/book3s_hv.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

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;
 	}
-- 
2.34.1