[Qemu-devel] [PATCH 2/2] ivshmem: validate incoming_posn value from server

[Stefan Hajnoczi]

Check incoming_posn to avoid out-of-bounds array accesses if the ivshmem
server on the host sends invalid values.

Cc: Cam Macdonell <c...@cs.ualberta.ca>
Reported-by: Sebastian Krahmer <krah...@suse.de>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
 hw/misc/ivshmem.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index 78363ce..25c22b7 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -383,6 +383,9 @@ static void close_guest_eventfds(IVShmemState *s, int posn)
     if (!ivshmem_has_feature(s, IVSHMEM_IOEVENTFD)) {
         return;
     }
+    if (posn < 0 || posn > s->nb_peers) {
+        return;
+    }
 
     guest_curr_max = s->peers[posn].nb_eventfds;
 
@@ -433,6 +436,12 @@ static void ivshmem_read(void *opaque, const uint8_t * 
buf, int size)
     }
 
     memcpy(&incoming_posn, buf, sizeof(long));
+
+    if (incoming_posn < -1) {
+        IVSHMEM_DPRINTF("invalid incoming_posn %ld\n", incoming_posn);
+        return;
+    }
+
     /* pick off s->server_chr->msgfd and store it, posn should accompany msg */
     tmp_fd = qemu_chr_fe_get_msgfd(s->server_chr);
     IVSHMEM_DPRINTF("posn is %ld, fd is %d\n", incoming_posn, tmp_fd);
-- 
1.9.0