[PATCH RESEND 04/10] via-cuda: Prevent read buffer overflow

From: Finn Thain
Date: Sat Dec 31 2016 - 19:58:37 EST


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@xxxxxxxxx>
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
---
drivers/macintosh/via-cuda.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/macintosh/via-cuda.c b/drivers/macintosh/via-cuda.c
index 64a04af..1cf1467 100644
--- 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();
--
2.10.2