chardev: clear O_NONBLOCK on SCM_RIGHTS file descriptors
When we receive a file descriptor over a UNIX domain socket the
O_NONBLOCK flag is preserved. Clear the O_NONBLOCK flag and rely on
QEMU file descriptor users like migration, SPICE, VNC, block layer, and
others to set non-blocking only when necessary.
This change ensures we don't accidentally expose O_NONBLOCK in the QMP
API. QMP clients should not need to get the non-blocking state
"correct".
A recent real-world example was when libvirt passed a non-blocking TCP
socket for migration where we expected a blocking socket. The source
QEMU produced a corrupted migration stream since its code did not cope
with non-blocking sockets.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/qemu-char.c b/qemu-char.c
index 4d8c6ca..d825b60 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2440,6 +2440,9 @@
if (fd < 0)
continue;
+ /* O_NONBLOCK is preserved across SCM_RIGHTS so reset it */
+ qemu_set_block(fd);
+
#ifndef MSG_CMSG_CLOEXEC
qemu_set_cloexec(fd);
#endif
