From 5eb0b194e9b01ba0f3613e6ddc2cb9f63ce96ae5 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Mon, 18 Apr 2016 13:07:35 +0300 Subject: cadence_uart: bounds check write offset MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit cadence_uart_init() initializes an I/O memory region of size 0x1000 bytes. However in uart_write(), the 'offset' parameter (offset within region) is divided by 4 and then used to index the array 'r' of size CADENCE_UART_R_MAX which is much smaller: (0x48/4). If 'offset>>=2' exceeds CADENCE_UART_R_MAX, this will cause an out-of-bounds memory write where the offset and the value are controlled by guest. This will corrupt QEMU memory, in most situations this causes the vm to crash. Fix by checking the offset against the array size. Cc: qemu-stable@nongnu.org Reported-by: 李强 Signed-off-by: Michael S. Tsirkin Reviewed-by: Alistair Francis Message-id: 20160418100735.GA517@redhat.com Signed-off-by: Peter Maydell --- hw/char/cadence_uart.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c index 486591bf07..797787823e 100644 --- a/hw/char/cadence_uart.c +++ b/hw/char/cadence_uart.c @@ -375,6 +375,9 @@ static void uart_write(void *opaque, hwaddr offset, DB_PRINT(" offset:%x data:%08x\n", (unsigned)offset, (unsigned)value); offset >>= 2; + if (offset >= CADENCE_UART_R_MAX) { + return; + } switch (offset) { case R_IER: /* ier (wts imr) */ s->r[R_IMR] |= value; -- cgit v1.2.1