x86/sgx: Add overflow check in sgx_validate_offset_length()

sgx_validate_offset_length() function verifies "offset" and "length"
arguments provided by userspace, but was missing an overflow check on
their addition. Add it.

Fixes: c6d26d3 ("x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES")
Signed-off-by: Borys Popławski <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Cc: [email protected] # v5.11+
Link: https://lore.kernel.org/r/[email protected]

Author: boryspoplawski

arch/x86/kernel/cpu/sgx/ioctl.c

@@ -356,6 +356,9 @@ static int sgx_validate_offset_length(struct sgx_encl *encl,
 	if (!length || !IS_ALIGNED(length, PAGE_SIZE))
 		return -EINVAL;
 
+	if (offset + length < offset)
+		return -EINVAL;
+
 	if (offset + length - PAGE_SIZE >= encl->size)
 		return -EINVAL;