linux-kernel - [PATCH] KVM: selftests: Fix mapping length truncation in m{,un}map()

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Message-ID: <20210624070931.565-1-yuzenghui@huawei.com>
Date:   Thu, 24 Jun 2021 15:09:31 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <pbonzini@...hat.com>, <vkuznets@...hat.com>
CC:     <wanghaibin.wang@...wei.com>, Zenghui Yu <yuzenghui@...wei.com>
Subject: [PATCH] KVM: selftests: Fix mapping length truncation in m{,un}map()

max_mem_slots is now declared as uint32_t. The result of (0x200000 * 32767)
is unexpectedly truncated to be 0xffe00000, whilst we actually need to
allocate about, 63GB. Cast max_mem_slots to size_t in both mmap() and
munmap() to fix the length truncation.

We'll otherwise see the failure on arm64 thanks to the access_ok() checking
in __kvm_set_memory_region(), as the unmapped VA happen to go beyond the
task's allowed address space.

 # ./set_memory_region_test
Allowed number of memory slots: 32767
Adding slots 0..32766, each memory region with 2048K size
==== Test Assertion Failure ====
  set_memory_region_test.c:391: ret == 0
  pid=94861 tid=94861 errno=22 - Invalid argument
     1	0x00000000004015a7: test_add_max_memory_regions at set_memory_region_test.c:389
     2	 (inlined by) main at set_memory_region_test.c:426
     3	0x0000ffffb8e67bdf: ?? ??:0
     4	0x00000000004016db: _start at :?
  KVM_SET_USER_MEMORY_REGION IOCTL failed,
  rc: -1 errno: 22 slot: 2615

Fixes: 3bf0fcd75434 ("KVM: selftests: Speed up set_memory_region_test")
Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
---
 tools/testing/selftests/kvm/set_memory_region_test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/set_memory_region_test.c b/tools/testing/selftests/kvm/set_memory_region_test.c
index d79d58eada9f..85b18bb8f762 100644
--- a/tools/testing/selftests/kvm/set_memory_region_test.c
+++ b/tools/testing/selftests/kvm/set_memory_region_test.c
@@ -376,7 +376,7 @@ static void test_add_max_memory_regions(void)
 	pr_info("Adding slots 0..%i, each memory region with %dK size\n",
 		(max_mem_slots - 1), MEM_REGION_SIZE >> 10);
 
-	mem = mmap(NULL, MEM_REGION_SIZE * max_mem_slots + alignment,
+	mem = mmap(NULL, (size_t)max_mem_slots * MEM_REGION_SIZE + alignment,
 		   PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 	TEST_ASSERT(mem != MAP_FAILED, "Failed to mmap() host");
 	mem_aligned = (void *)(((size_t) mem + alignment - 1) & ~(alignment - 1));
@@ -401,7 +401,7 @@ static void test_add_max_memory_regions(void)
 	TEST_ASSERT(ret == -1 && errno == EINVAL,
 		    "Adding one more memory slot should fail with EINVAL");
 
-	munmap(mem, MEM_REGION_SIZE * max_mem_slots + alignment);
+	munmap(mem, (size_t)max_mem_slots * MEM_REGION_SIZE + alignment);
 	munmap(mem_extra, MEM_REGION_SIZE);
 	kvm_vm_free(vm);
 }
-- 
2.19.1