From 4ab4183d766f10f9fc35cd9ef4acee39f241986f Mon Sep 17 00:00:00 2001 From: "David S. Ahern" Date: Wed, 3 Feb 2010 09:00:54 -0700 Subject: [PATCH] segfault due to buffer overrun in usb-serial This fixes a segfault due to buffer overrun in the usb-serial device. The memcpy was incrementing the start location by recv_used yet, the computation of first_size (how much to write at the end of the buffer before wrapping to the front) was not accounting for it. This causes the next element after the receive buffer (recv_ptr) to get overwritten with random data. Signed-off-by: David Ahern Signed-off-by: Anthony Liguori --- hw/usb-serial.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/hw/usb-serial.c b/hw/usb-serial.c index 37293ea410..c3f3401370 100644 --- a/hw/usb-serial.c +++ b/hw/usb-serial.c @@ -497,12 +497,28 @@ static int usb_serial_can_read(void *opaque) static void usb_serial_read(void *opaque, const uint8_t *buf, int size) { USBSerialState *s = opaque; - int first_size = RECV_BUF - s->recv_ptr; - if (first_size > size) - first_size = size; - memcpy(s->recv_buf + s->recv_ptr + s->recv_used, buf, first_size); - if (size > first_size) - memcpy(s->recv_buf, buf + first_size, size - first_size); + int first_size, start; + + /* room in the buffer? */ + if (size > (RECV_BUF - s->recv_used)) + size = RECV_BUF - s->recv_used; + + start = s->recv_ptr + s->recv_used; + if (start < RECV_BUF) { + /* copy data to end of buffer */ + first_size = RECV_BUF - start; + if (first_size > size) + first_size = size; + + memcpy(s->recv_buf + start, buf, first_size); + + /* wrap around to front if needed */ + if (size > first_size) + memcpy(s->recv_buf, buf + first_size, size - first_size); + } else { + start -= RECV_BUF; + memcpy(s->recv_buf + start, buf, size); + } s->recv_used += size; }