[Qemu-devel] [PATCH] Fix bug with virtio-9p fsync

[Sassan Panahinejad <sassan@sassan.me.uk>]

v9fs_fsync and possibly others break when asked to operate on a directory.
It does not check fid_type to see if it is operating on a directory and therefore accesses the wrong element of the fs union.
This error can result in guest applications failing (in my case it was dpkg).
This patch fixes the issue, although there may be other, similar bugs in virtio-9p.

Signed-off-by: Sassan Panahinejad <sassan@sassan.me.uk>
---
 hw/virtio-9p.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index 7e29535..cc4fdc8 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -1875,7 +1875,11 @@ static void v9fs_fsync(V9fsState *s, V9fsPDU *pdu)
         v9fs_post_do_fsync(s, pdu, err);
         return;
     }
-    err = v9fs_do_fsync(s, fidp->fs.fd, datasync);
+    if (fidp->fid_type == P9_FID_DIR) {
+        err = v9fs_do_fsync(s, dirfd(fidp->fs.dir), datasync);
+    } else {
+        err = v9fs_do_fsync(s, fidp->fs.fd, datasync);
+    }
     v9fs_post_do_fsync(s, pdu, err);
 }
 
-- 
1.7.0.4