1 files changed, 26 insertions, 29 deletions

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 823cf5f5196b..7150e5c23604 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -237,16 +237,13 @@ EXPORT_SYMBOL_GPL(mpi_get_buffer);
  * @a:          a multi precision integer
  * @sgl:        scatterlist to write to. Needs to be at least
  *              mpi_get_size(a) long.
- * @nbytes:     in/out param - it has the be set to the maximum number of
- *              bytes that can be written to sgl. This has to be at least
- *              the size of the integer a. On return it receives the actual
- *              length of the data written on success or the data that would
- *              be written if buffer was too small.
+ * @nbytes:     the number of bytes to write.  Leading bytes will be
+ *              filled with zero.
  * @sign:       if not NULL, it will be set to the sign of a.
  *
  * Return:      0 on success or error code in case of error
  */
-int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
+int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned nbytes,
                      int *sign)
 {
         u8 *p, *p2;
@@ -258,43 +255,44 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
 #error please implement for this limb size.
 #endif
         unsigned int n = mpi_get_size(a);
-        int i, x, y = 0, lzeros, buf_len;
-
-        if (!nbytes)
-                return -EINVAL;
+        int i, x, buf_len;
 
         if (sign)
                 *sign = a->sign;
 
-        lzeros = count_lzeros(a);
-
-        if (*nbytes < n - lzeros) {
-                *nbytes = n - lzeros;
+        if (nbytes < n)
                 return -EOVERFLOW;
-        }
 
-        *nbytes = n - lzeros;
         buf_len = sgl->length;
         p2 = sg_virt(sgl);
 
-        for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
-                        lzeros %= BYTES_PER_MPI_LIMB;
-                i >= 0; i--) {
+        while (nbytes > n) {
+                if (!buf_len) {
+                        sgl = sg_next(sgl);
+                        if (!sgl)
+                                return -EINVAL;
+                        buf_len = sgl->length;
+                        p2 = sg_virt(sgl);
+                }
+
+                i = min_t(unsigned, nbytes - n, buf_len);
+                memset(p2, 0, i);
+                p2 += i;
+                buf_len -= i;
+                nbytes -= i;
+        }
+
+        for (i = a->nlimbs - 1; i >= 0; i--) {
 #if BYTES_PER_MPI_LIMB == 4
-                alimb = cpu_to_be32(a->d[i]);
+                alimb = a->d[i] ? cpu_to_be32(a->d[i]) : 0;
 #elif BYTES_PER_MPI_LIMB == 8
-                alimb = cpu_to_be64(a->d[i]);
+                alimb = a->d[i] ? cpu_to_be64(a->d[i]) : 0;
 #else
 #error please implement for this limb size.
 #endif
-                if (lzeros) {
-                        y = lzeros;
-                        lzeros = 0;
-                }
-
-                p = (u8 *)&alimb + y;
+                p = (u8 *)&alimb;
 
-                for (x = 0; x < sizeof(alimb) - y; x++) {
+                for (x = 0; x < sizeof(alimb); x++) {
                         if (!buf_len) {
                                 sgl = sg_next(sgl);
                                 if (!sgl)
@@ -305,7 +303,6 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
                         *p2++ = *p++;
                         buf_len--;
                 }
-                y = 0;
         }
         return 0;
 }