MPILIB: add mpi_read_buf() and mpi_get_size() helpers

Added a mpi_read_buf() helper function to export MPI to a buf provided by
the user, and a mpi_get_size() helper, that tells the user how big the buf is.
Changed mpi_free to use kzfree instead of kfree because it is used to free
crypto keys.

Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

2 files changed, 71 insertions, 22 deletions

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 4cc6442733f4..bc0a1da8afba 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -128,28 +128,36 @@ leave:
 }
 EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
 
-/****************
- * Return an allocated buffer with the MPI (msb first).
- * NBYTES receives the length of this buffer. Caller must free the
- * return string (This function does return a 0 byte buffer with NBYTES
- * set to zero if the value of A is zero. If sign is not NULL, it will
- * be set to the sign of the A.
+/**
+ * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
+ *
+ * @a:          a multi precision integer
+ * @buf:        bufer to which the output will be written to. Needs to be at
+ *              leaset mpi_get_size(a) long.
+ * @buf_len:    size of the buf.
+ * @nbytes:     receives the actual length of the data written.
+ * @sign:       if not NULL, it will be set to the sign of a.
+ *
+ * Return:      0 on success or error code in case of error
  */
-void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
+int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
+                    int *sign)
 {
-        uint8_t *p, *buffer;
+        uint8_t *p;
         mpi_limb_t alimb;
+        unsigned int n = mpi_get_size(a);
         int i;
-        unsigned int n;
+
+        if (buf_len < n || !buf)
+                return -EINVAL;
 
         if (sign)
                 *sign = a->sign;
-        *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
-        if (!n)
-                n++;            /* avoid zero length allocation */
-        p = buffer = kmalloc(n, GFP_KERNEL);
-        if (!p)
-                return NULL;
+
+        if (nbytes)
+                *nbytes = n;
+
+        p = buf;
 
         for (i = a->nlimbs - 1; i >= 0; i--) {
                 alimb = a->d[i];
@@ -171,15 +179,56 @@ void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
 #error please implement for this limb size.
 #endif
         }
+        return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_read_buffer);
+
+/*
+ * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
+ * Caller must free the return string.
+ * This function does return a 0 byte buffer with nbytes set to zero if the
+ * value of A is zero.
+ *
+ * @a:          a multi precision integer.
+ * @nbytes:     receives the length of this buffer.
+ * @sign:       if not NULL, it will be set to the sign of the a.
+ *
+ * Return:      Pointer to MPI buffer or NULL on error
+ */
+void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
+{
+        uint8_t *buf, *p;
+        unsigned int n;
+        int ret;
+
+        if (!nbytes)
+                return NULL;
+
+        n = mpi_get_size(a);
+
+        if (!n)
+                n++;
+
+        buf = kmalloc(n, GFP_KERNEL);
+
+        if (!buf)
+                return NULL;
+
+        ret = mpi_read_buffer(a, buf, n, nbytes, sign);
+
+        if (ret) {
+                kfree(buf);
+                return NULL;
+        }
 
         /* this is sub-optimal but we need to do the shift operation
          * because the caller has to free the returned buffer */
-        for (p = buffer; !*p && *nbytes; p++, --*nbytes)
+        for (p = buf; !*p && *nbytes; p++, --*nbytes)
                 ;
-        if (p != buffer)
-                memmove(buffer, p, *nbytes);
+        if (p != buf)
+                memmove(buf, p, *nbytes);
 
-        return buffer;
+        return buf;
 }
 EXPORT_SYMBOL_GPL(mpi_get_buffer);
 
diff --git a/lib/mpi/mpiutil.c b/lib/mpi/mpiutil.c
index bf076d281d40..314f4dfa603e 100644
--- a/lib/mpi/mpiutil.c
+++ b/lib/mpi/mpiutil.c
@@ -69,7 +69,7 @@ void mpi_free_limb_space(mpi_ptr_t a)
         if (!a)
                 return;
 
-        kfree(a);
+        kzfree(a);
 }
 
 void mpi_assign_limb_space(MPI a, mpi_ptr_t ap, unsigned nlimbs)
@@ -95,7 +95,7 @@ int mpi_resize(MPI a, unsigned nlimbs)
                 if (!p)
                         return -ENOMEM;
                 memcpy(p, a->d, a->alloced * sizeof(mpi_limb_t));
-                kfree(a->d);
+                kzfree(a->d);
                 a->d = p;
         } else {
                 a->d = kzalloc(nlimbs * sizeof(mpi_limb_t), GFP_KERNEL);
@@ -112,7 +112,7 @@ void mpi_free(MPI a)
                 return;
 
         if (a->flags & 4)
-                kfree(a->d);
+                kzfree(a->d);
         else
                 mpi_free_limb_space(a->d);