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

From: Sasha Levin
Date: Mon Jan 17 2022 - 12:04:22 EST


From: Alexey Kardashevskiy <aik@xxxxxxxxx>

[ 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@xxxxxxxxx>
[mpe: Use 'size' for the variable rather than 'cb']
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210901084512.1658628-1-aik@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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