s390x/sclpconsole-lm: truncate input if line is too long

As the SCLP line mode console input length is limited by the available
SCCB buffer space, it might lock up if the input does not fit into the
buffer.

With this patch, characters that don't fit are 'eaten' up to the next
CR/LF and the input line is sent truncated to the guest.

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/hw/char/sclpconsole-lm.c b/hw/char/sclpconsole-lm.c
index 80dd0a9..605dd50 100644
--- a/hw/char/sclpconsole-lm.c
+++ b/hw/char/sclpconsole-lm.c
@@ -52,7 +52,8 @@ typedef struct SCLPConsoleLM {
  * event_pending is set when a newline character is encountered
  *
  * The maximum command line length is limited by the maximum
- * space available in an SCCB
+ * space available in an SCCB. Line mode console input is sent
+ * truncated to the guest in case it doesn't fit into the SCCB.
  */
 
 static int chr_can_read(void *opaque)
@@ -61,10 +62,8 @@ static int chr_can_read(void *opaque)
 
     if (scon->event.event_pending) {
         return 0;
-    } else if (SIZE_CONSOLE_BUFFER - scon->length) {
-        return 1;
     }
-    return 0;
+    return 1;
 }
 
 static void chr_read(void *opaque, const uint8_t *buf, int size)
@@ -78,6 +77,10 @@ static void chr_read(void *opaque, const uint8_t *buf, int size)
         sclp_service_interrupt(0);
         return;
     }
+    if (scon->length == SIZE_CONSOLE_BUFFER) {
+        /* Eat the character, but still process CR and LF.  */
+        return;
+    }
     scon->buf[scon->length] = *buf;
     scon->length += 1;
     if (scon->echo) {