Merge patch series "credentials guards: the easy cases"

Christian Brauner <brauner@kernel.org> says:

This converts all users of override_creds() to rely on credentials
guards. Leave all those that do the prepare_creds() + modify creds +
override_creds() dance alone for now. Some of them qualify for their own
variant.

* patches from https://patch.msgid.link/20251103-work-creds-guards-simple-v1-0-a3e156839e7f@kernel.org:
  net/dns_resolver: use credential guards in dns_query()
  cgroup: use credential guards in cgroup_attach_permissions()
  act: use credential guards in acct_write_process()
  smb: use credential guards in cifs_get_spnego_key()
  nfs: use credential guards in nfs_idmap_get_key()
  nfs: use credential guards in nfs_local_call_write()
  nfs: use credential guards in nfs_local_call_read()
  erofs: use credential guards
  binfmt_misc: use credential guards
  backing-file: use credential guards for mmap
  backing-file: use credential guards for splice write
  backing-file: use credential guards for splice read
  backing-file: use credential guards for writes
  backing-file: use credential guards for reads
  aio: use credential guards
  cred: add {scoped_}with_creds() guards

Link: https://patch.msgid.link/20251103-work-creds-guards-simple-v1-0-a3e156839e7f@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>