9pfs: fix removing non-existent POSIX ACL xattr on macOS host

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>
Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-Id: <34f81e9bffd7a3e65fb7aab5b56c107bd0aac960.1651228001.git.qemu_oss@crudebyte.com>

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