From 6f7e1d2bddb5a0a1c65f6f02467460d6edbcc901 Mon Sep 17 00:00:00 2001

From: "Daniel P. Berrange" <berrange@redhat.com>

Date: Tue, 1 Oct 2013 12:28:17 +0100

Subject: [PATCH] hw/9pfs: Fix errno value for xattr functions

If there is no operation driver for the xattr type the

functions return '-1' and set errno to '-EOPNOTSUPP'.

When the calling code sets 'ret = -errno' this turns

into a large positive number.

In Linux 3.11, the kernel has switched to using 9p

version 9p2000.L, instead of 9p2000.u, which enables

support for xattr operations. This on its own is harmless,

but for another change which makes it request the xattr

with a name 'security.capability'.

The result is that the guest sees a succesful return

of 95 bytes of data, instead of a failure with errno

set to 95. Since the kernel expects a maximum of 20

bytes for an xattr return this gets translated to the

unexpected errno ERANGE.

This all means that when running a binary off a 9p fs

in 3.11 kernels you get a fun result of:

  # ./date

  sh: ./date: Numerical result out of range

The only workaround is to pass 'version=9p2000.u' when

mounting the 9p fs in the guest, to disable all use of

xattrs.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

---

 hw/9pfs/virtio-9p-xattr.c | 6 +++---

 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/9pfs/virtio-9p-xattr.c b/hw/9pfs/virtio-9p-xattr.c

index 90ae565..3fae557 100644

--- a/hw/9pfs/virtio-9p-xattr.c

+++ b/hw/9pfs/virtio-9p-xattr.c

@@ -36,7 +36,7 @@ ssize_t v9fs_get_xattr(FsContext *ctx, const char *path,

     if (xops) {

         return xops->getxattr(ctx, path, name, value, size);

     }

-    errno = -EOPNOTSUPP;

+    errno = EOPNOTSUPP;

     return -1;

 }

@@ -123,7 +123,7 @@ int v9fs_set_xattr(FsContext *ctx, const char *path, const char *name,

     if (xops) {

         return xops->setxattr(ctx, path, name, value, size, flags);

     }

-    errno = -EOPNOTSUPP;

+    errno = EOPNOTSUPP;

     return -1;

 }

@@ -135,7 +135,7 @@ int v9fs_remove_xattr(FsContext *ctx,

     if (xops) {

         return xops->removexattr(ctx, path, name);

     }

-    errno = -EOPNOTSUPP;

+    errno = EOPNOTSUPP;

     return -1;

 }