Re: [PATCH v2 5/5] 9pfs: fix removing non-existent POSIX ACL xattr on macOS host

[Greg Kurz]

On Thu, 21 Apr 2022 17:07:55 +0200
Christian Schoenebeck <qemu_oss@crudebyte.com> wrote:

> When mapped POSIX ACL is used, we are ignoring errors when trying
> to remove a POSIX ACL xattr that does not exist. On Linux hosts we
> would get ENODATA in such cases, on macOS hosts however we get
> ENOATTR instead.
> 
> As we can be sure that ENOATTR is defined as being identical on Linux
> hosts (at least by qemu/xattr.h), it is safe to fix this issue by
> simply comparing against ENOATTR instead of ENODATA.
> 
> This patch fixes e.g. a command on Linux guest like:
> 
>   cp --preserve=mode old new
> 
> Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> Link: https://lore.kernel.org/qemu-devel/2866993.yOYK24bMf6@silver/
> ---

Reviewed-by: Greg Kurz <groug@kaod.org>

>  hw/9pfs/9p-posix-acl.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/9pfs/9p-posix-acl.c b/hw/9pfs/9p-posix-acl.c
> index eadae270dd..4b2cb3c66c 100644
> --- a/hw/9pfs/9p-posix-acl.c
> +++ b/hw/9pfs/9p-posix-acl.c
> @@ -65,7 +65,11 @@ static int mp_pacl_removexattr(FsContext *ctx,
>      int ret;
>  
>      ret = local_removexattr_nofollow(ctx, path, MAP_ACL_ACCESS);
> -    if (ret == -1 && errno == ENODATA) {
> +    /*
> +     * macOS returns ENOATTR (!=ENODATA on macOS), whereas Linux returns
> +     * ENODATA (==ENOATTR on Linux), so checking for ENOATTR is fine
> +     */
> +    if (ret == -1 && errno == ENOATTR) {
>          /*
>           * We don't get ENODATA error when trying to remove a
>           * posix acl that is not present. So don't throw the error
> @@ -115,7 +119,11 @@ static int mp_dacl_removexattr(FsContext *ctx,
>      int ret;
>  
>      ret = local_removexattr_nofollow(ctx, path, MAP_ACL_DEFAULT);
> -    if (ret == -1 && errno == ENODATA) {
> +    /*
> +     * macOS returns ENOATTR (!=ENODATA on macOS), whereas Linux returns
> +     * ENODATA (==ENOATTR on Linux), so checking for ENOATTR is fine
> +     */
> +    if (ret == -1 && errno == ENOATTR) {
>          /*
>           * We don't get ENODATA error when trying to remove a
>           * posix acl that is not present. So don't throw the error