tty/vt: consolemap: walk the buffer only once in con_set_trans_old()

Fetch the user data one by one (by get_user()) and fill in the local
buffer simultaneously. I.e. we no longer require to walk two buffers and
save thus 256 B from stack (whole ubuf).

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-36-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
index f97f7ee6268b21f851bccb44c8ea654726bae95d..fff97ae87e00e0f3a308044c14bb571bcf452f47 100644 (file)
--- a/drivers/tty/vt/consolemap.c
+++ b/drivers/tty/vt/consolemap.c
@@ -343,15 +343,15 @@ static void update_user_maps(void)
  */
 int con_set_trans_old(unsigned char __user * arg)
 {
-       int i;
        unsigned short inbuf[E_TABSZ];
-       unsigned char ubuf[E_TABSZ];
-
-       if (copy_from_user(ubuf, arg, E_TABSZ))
-               return -EFAULT;
+       unsigned int i;
+       unsigned char ch;
 
-       for (i = 0; i < E_TABSZ ; i++)
-               inbuf[i] = UNI_DIRECT_BASE | ubuf[i];
+       for (i = 0; i < ARRAY_SIZE(inbuf); i++) {
+               if (get_user(ch, &arg[i]))
+                       return -EFAULT;
+               inbuf[i] = UNI_DIRECT_BASE | ch;
+       }
 
        console_lock();
        memcpy(translations[USER_MAP], inbuf, sizeof(inbuf));