[PATCH 5.10.y] KVM: s390: Fix length check __import_wp_info()

[Sasha Levin <sashal@kernel.org>]

From: Christian Borntraeger <borntraeger@linux.ibm.com>

[ Upstream commit 4c07680a467e2f7697245bcd11691bffb2a6f0ed ]

struct kvm_hw_breakpoint::len is a __u64 that is fully controlled by user
space. This is then assigned to wp_info->len, which is an int. The bounds
check is done on the truncated value while the allocation uses the
untruncated one:

	wp_info->len = bp_data->len;
	[...]
	if (wp_info->len < 0 || wp_info->len > MAX_WP_SIZE)
		return -EINVAL;

	wp_info->old_data = kmalloc(bp_data->len, GFP_KERNEL_ACCOUNT);

Use the validated value for the allocation as intended. Without this
fix userspace can trigger >4GB allocations which will fail and result
in a WARN due to MAX_PAGE_ORDER.

Fixes: 27291e2165b6 ("KVM: s390: hardware support for guest debugging")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260805110455.7200-9-borntraeger@linux.ibm.com>
[ Retained GFP_KERNEL instead of upstream GFP_KERNEL_ACCOUNT in the kmalloc() call. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/s390/kvm/guestdbg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kvm/guestdbg.c b/arch/s390/kvm/guestdbg.c
index 394a5f53805ba..de3fa79fb0751 100644
--- a/arch/s390/kvm/guestdbg.c
+++ b/arch/s390/kvm/guestdbg.c
@@ -184,7 +184,7 @@ static int __import_wp_info(struct kvm_vcpu *vcpu,
 	if (wp_info->len < 0 || wp_info->len > MAX_WP_SIZE)
 		return -EINVAL;
 
-	wp_info->old_data = kmalloc(bp_data->len, GFP_KERNEL);
+	wp_info->old_data = kmalloc(wp_info->len, GFP_KERNEL);
 	if (!wp_info->old_data)
 		return -ENOMEM;
 	/* try to backup the original value */
-- 
2.53.0