linux-kernel - [PATCH] KVM: use struct_size() and flex_array_size() helpers in kvm_io_bus_unregister

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Date:   Fri, 18 Sep 2020 05:05:00 -0700
From:   Rustam Kovhaev <rkovhaev@...il.com>
To:     pbonzini@...hat.com, vkuznets@...hat.com, gustavoars@...nel.org,
        kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        stable@...r.kernel.org, Rustam Kovhaev <rkovhaev@...il.com>
Subject: [PATCH] KVM: use struct_size() and flex_array_size() helpers in kvm_io_bus_unregister_dev()

Make use of the struct_size() helper to avoid any potential type
mistakes and protect against potential integer overflows
Make use of the flex_array_size() helper to calculate the size of a
flexible array member within an enclosing structure

Cc: stable@...r.kernel.org
Suggested-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Signed-off-by: Rustam Kovhaev <rkovhaev@...il.com>
---
 virt/kvm/kvm_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cf88233b819a..68edd25dcb11 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4350,10 +4350,10 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
 	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
 			  GFP_KERNEL_ACCOUNT);
 	if (new_bus) {
-		memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
+		memcpy(new_bus, bus, struct_size(bus, range, i));
 		new_bus->dev_count--;
 		memcpy(new_bus->range + i, bus->range + i + 1,
-		       (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
+				flex_array_size(new_bus, range, new_bus->dev_count - i));
 	} else {
 		pr_err("kvm: failed to shrink bus, removing it completely\n");
 		for (j = 0; j < bus->dev_count; j++) {
-- 
2.28.0