via-cuda: Prevent read buffer overflow

If the Cuda driver does not enter the 'read_done' state for some
reason, it may continue in the 'reading' state until the buffer
overflows. Add a bounds check to prevent this.

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/drivers/macintosh/via-cuda.c b/drivers/macintosh/via-cuda.c
index 64a04af248a1a75e909bd467fea4dbd135e235de..1cf1467cf6e54f6af2a7f6e5520b2a7cf834bb7e 100644 (file)
--- a/drivers/macintosh/via-cuda.c
+++ b/drivers/macintosh/via-cuda.c
@@ -470,6 +470,8 @@ cuda_poll(void)
 }
 EXPORT_SYMBOL(cuda_poll);
 
+#define ARRAY_FULL(a, p)       ((p) - (a) == ARRAY_SIZE(a))
+
 static irqreturn_t
 cuda_interrupt(int irq, void *arg)
 {
@@ -558,7 +560,11 @@ cuda_interrupt(int irq, void *arg)
        break;
 
     case reading:
-       *reply_ptr++ = in_8(&via[SR]);
+       if (reading_reply ? ARRAY_FULL(current_req->reply, reply_ptr)
+                         : ARRAY_FULL(cuda_rbuf, reply_ptr))
+           (void)in_8(&via[SR]);
+       else
+           *reply_ptr++ = in_8(&via[SR]);
        if (!TREQ_asserted(status)) {
            /* that's all folks */
            negate_TIP_and_TACK();