crypto: x86/aes-ni - add missing error checks in XTS code

The updated XTS code fails to check the return code of skcipher_walk_virt,
which may lead to skcipher_walk_abort() or skcipher_walk_done() being called
while the walk argument is in an inconsistent state.

So check the return value after each such call, and bail on errors.

Fixes: 2481104fe98d ("crypto: x86/aes-ni-xts - rewrite and drop indirections via glue helper")
Reported-by: Dave Hansen <[e-mail]>
Reported-by: syzbot <[e-mail]>
Signed-off-by: Ard Biesheuvel <[e-mail]>
Reviewed-by: Eric Biggers <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

arch/x86/crypto/aesni-intel_glue.c

···
 		return -EINVAL;
 
 	err = skcipher_walk_virt(&walk, req, false);
+	if (err)
+		return err;
 
 	if (unlikely(tail > 0 && walk.nbytes < walk.total)) {
 		int blocks = DIV_ROUND_UP(req->cryptlen, AES_BLOCK_SIZE) - 2;
···
 		skcipher_request_set_crypt(&subreq, req->src, req->dst,
 					   blocks * AES_BLOCK_SIZE, req->iv);
 		req = &subreq;
+
 		err = skcipher_walk_virt(&walk, req, false);
+		if (err)
+			return err;
 	} else {
 		tail = 0;
 	}