[Qemu-devel] [PATCH 1/2] ivshmem: check ivshmem_read() size argument

[Stefan Hajnoczi <stefanha@redhat.com>]

The third argument to the fd_read() callback implemented by
ivshmem_read() is the number of bytes, not a flags field.  Fix this and
check we received enough bytes before accessing the buffer pointer.

Cc: Cam Macdonell <cam@cs.ualberta.ca>
Reported-by: Sebastian Krahmer <krahmer@suse.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/misc/ivshmem.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index 8d144ba..78363ce 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -420,13 +420,18 @@ static void increase_dynamic_storage(IVShmemState *s, int new_min_size) {
     }
 }
 
-static void ivshmem_read(void *opaque, const uint8_t * buf, int flags)
+static void ivshmem_read(void *opaque, const uint8_t * buf, int size)
 {
     IVShmemState *s = opaque;
     int incoming_fd, tmp_fd;
     int guest_max_eventfd;
     long incoming_posn;
 
+    if (size < sizeof(incoming_posn)) {
+        IVSHMEM_DPRINTF("short read of %d bytes\n", size);
+        return;
+    }
+
     memcpy(&incoming_posn, buf, sizeof(long));
     /* pick off s->server_chr->msgfd and store it, posn should accompany msg */
     tmp_fd = qemu_chr_fe_get_msgfd(s->server_chr);
-- 
1.9.0