tile gxio: use better string copy primitive

[cascardo/linux.git] / arch / tile / gxio / mpipe.c

diff --git a/arch/tile/gxio/mpipe.c b/arch/tile/gxio/mpipe.c
index 5301a9f..320ff5e 100644 (file)
--- a/arch/tile/gxio/mpipe.c
+++ b/arch/tile/gxio/mpipe.c
@@ -29,6 +29,32 @@
 /* HACK: Avoid pointless "shadow" warnings. */
 #define link link_shadow
 
+/**
+ * strscpy - Copy a C-string into a sized buffer, but only if it fits
+ * @dest: Where to copy the string to
+ * @src: Where to copy the string from
+ * @size: size of destination buffer
+ *
+ * Use this routine to avoid copying too-long strings.
+ * The routine returns the total number of bytes copied
+ * (including the trailing NUL) or zero if the buffer wasn't
+ * big enough.  To ensure that programmers pay attention
+ * to the return code, the destination has a single NUL
+ * written at the front (if size is non-zero) when the
+ * buffer is not big enough.
+ */
+static size_t strscpy(char *dest, const char *src, size_t size)
+{
+       size_t len = strnlen(src, size) + 1;
+       if (len > size) {
+               if (size)
+                       dest[0] = '\0';
+               return 0;
+       }
+       memcpy(dest, src, len);
+       return len;
+}
+
 int gxio_mpipe_init(gxio_mpipe_context_t *context, unsigned int mpipe_index)
 {
        char file[32];
@@ -511,8 +537,8 @@ int gxio_mpipe_link_instance(const char *link_name)
        if (!context)
                return GXIO_ERR_NO_DEVICE;
 
-       strncpy(name.name, link_name, sizeof(name.name));
-       name.name[GXIO_MPIPE_LINK_NAME_LEN - 1] = '\0';
+       if (strscpy(name.name, link_name, sizeof(name.name)) == 0)
+               return GXIO_ERR_NO_DEVICE;
 
        return gxio_mpipe_info_instance_aux(context, name);
 }
@@ -529,7 +555,8 @@ int gxio_mpipe_link_enumerate_mac(int idx, char *link_name, uint8_t *link_mac)
 
        rv = gxio_mpipe_info_enumerate_aux(context, idx, &name, &mac);
        if (rv >= 0) {
-               strncpy(link_name, name.name, sizeof(name.name));
+               if (strscpy(link_name, name.name, sizeof(name.name)) == 0)
+                       return GXIO_ERR_INVAL_MEMORY_SIZE;
                memcpy(link_mac, mac.mac, sizeof(mac.mac));
        }
 
@@ -545,8 +572,8 @@ int gxio_mpipe_link_open(gxio_mpipe_link_t *link,
        _gxio_mpipe_link_name_t name;
        int rv;
 
-       strncpy(name.name, link_name, sizeof(name.name));
-       name.name[GXIO_MPIPE_LINK_NAME_LEN - 1] = '\0';
+       if (strscpy(name.name, link_name, sizeof(name.name)) == 0)
+               return GXIO_ERR_NO_DEVICE;
 
        rv = gxio_mpipe_link_open_aux(context, name, flags);
        if (rv < 0)