lib/mpi: only require buffers as big as needed for the integer
Since mpi_write_to_sgl and mpi_read_buffer explicitly left-align the
integers being written it makes no sense to require a buffer big enough for
the number + the leading zero bytes which are not written. The error
returned also doesn't convey any information. So instead require only the
size needed and return -EOVERFLOW to signal when buffer too short.
Signed-off-by: Andrew Zaborowski <andrew.zaborowski@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 3db76b8..ec533a6 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -135,7 +135,9 @@
* @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.
+ * @nbytes: receives the actual length of the data written on success and
+ * the data to-be-written on -EOVERFLOW in case buf_len was too
+ * small.
* @sign: if not NULL, it will be set to the sign of a.
*
* Return: 0 on success or error code in case of error
@@ -148,7 +150,7 @@
unsigned int n = mpi_get_size(a);
int i, lzeros = 0;
- if (buf_len < n || !buf || !nbytes)
+ if (!buf || !nbytes)
return -EINVAL;
if (sign)
@@ -163,6 +165,11 @@
break;
}
+ if (buf_len < n - lzeros) {
+ *nbytes = n - lzeros;
+ return -EOVERFLOW;
+ }
+
p = buf;
*nbytes = n - lzeros;
@@ -332,7 +339,8 @@
* @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.
+ * length of the data written on success or the data that would
+ * be written if buffer was too small.
* @sign: if not NULL, it will be set to the sign of a.
*
* Return: 0 on success or error code in case of error
@@ -345,7 +353,7 @@
unsigned int n = mpi_get_size(a);
int i, x, y = 0, lzeros = 0, buf_len;
- if (!nbytes || *nbytes < n)
+ if (!nbytes)
return -EINVAL;
if (sign)
@@ -360,6 +368,11 @@
break;
}
+ if (*nbytes < n - lzeros) {
+ *nbytes = n - lzeros;
+ return -EOVERFLOW;
+ }
+
*nbytes = n - lzeros;
buf_len = sgl->length;
p2 = sg_virt(sgl);