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Re: [Qemu-trivial] [PATCH] hw/9pfs: Fix errno value for xattr functions
From: |
Aneesh Kumar K.V |
Subject: |
Re: [Qemu-trivial] [PATCH] hw/9pfs: Fix errno value for xattr functions |
Date: |
Tue, 01 Oct 2013 21:53:20 +0530 |
User-agent: |
Notmuch/0.16+84~gcbbf53e (http://notmuchmail.org) Emacs/24.2.1 (x86_64-pc-linux-gnu) |
"Daniel P. Berrange" <address@hidden> writes:
> From: "Daniel P. Berrange" <address@hidden>
>
> 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 <address@hidden>
Reviewed-by: Aneesh Kumar K.V <address@hidden>
> ---
> 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;
>
> }
> --
> 1.8.3.1