lib/mpi: Fix SG miter leak

In mpi_read_raw_from_sgl we may leak the SG miter resouces after
reading the leading zeroes.  This patch fixes this by stopping the
iteration once the leading zeroes have been read.

Fixes: 127827b9 ("lib/mpi: Do not do sg_virt")
Reported-by: Nicolai Stange <nicstange@gmail.com>
Tested-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

lib/mpi/mpicoder.c

@@ -363,6 +363,9 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
 		lzeros = 0;
 	}
 
+	miter.consumed = lzeros;
+	sg_miter_stop(&miter);
+
 	nbytes -= lzeros;
 	nbits = nbytes * 8;
 	if (nbits > MAX_EXTERN_MPI_BITS) {
@@ -390,7 +393,10 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
 	z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
 	z %= BYTES_PER_MPI_LIMB;
 
-	for (;;) {
+	while (sg_miter_next(&miter)) {
+		buff = miter.addr;
+		len = miter.length;
+
 		for (x = 0; x < len; x++) {
 			a <<= 8;
 			a |= *buff++;
@@ -400,12 +406,6 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
 			}
 		}
 		z += x;
-
-		if (!sg_miter_next(&miter))
-			break;
-
-		buff = miter.addr;
-		len = miter.length;
 	}
 
 	return val;