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> On Aug 10, 2017, at 4:41 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
> For a while now any NFSv2 mount where sec= is specified uses
> AUTH_NULL. If sec= is not specified, the mount uses AUTH_UNIX.
> Commit e68fd7c8071d ("mount: use sec= that was specified on the
> command line") attempted to address a very similar problem with
> NFSv3, and should have fixed this too, but it has a bug.
>
> The MNTv1 MNT procedure does not return a list of security flavors,
> so our client makes up a list containing just AUTH_NULL. This should
> enable nfs_verify_authflavors() to assign the sec= specified flavor,
> but instead, it incorrectly sets it to AUTH_NULL.
>
> I expect this would also be a problem for any NFSv3 server whose
> MNTv3 MNT procedure returned a security flavor list containing only
> AUTH_NULL.
>
> Fixes: e68fd7c8071d ("mount: use sec= that was specified on ... ")
> BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=310
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> fs/nfs/super.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> Changes since v1:
> - Description edited for accuracy
>
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index d828ef8..6b179af 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -1691,8 +1691,8 @@ static int nfs_verify_authflavors(struct nfs_parsed_mount_data *args,
> rpc_authflavor_t *server_authlist, unsigned int count)
> {
> rpc_authflavor_t flavor = RPC_AUTH_MAXFLAVOR;
> + bool found_auth_null = false;
> unsigned int i;
> - int use_auth_null = false;
>
> /*
> * If the sec= mount option is used, the specified flavor or AUTH_NULL
> @@ -1701,6 +1701,10 @@ static int nfs_verify_authflavors(struct nfs_parsed_mount_data *args,
> * AUTH_NULL has a special meaning when it's in the server list - it
> * means that the server will ignore the rpc creds, so any flavor
> * can be used but still use the sec= that was specified.
> + *
> + * Note also that the MNT procedure in MNTv1 does not return a list
> + * of supported security flavors. In this case, nfs_mount() fabricates
> + * a security flavor list containing just AUTH_NULL.
> */
> for (i = 0; i < count; i++) {
> flavor = server_authlist[i];
> @@ -1709,11 +1713,11 @@ static int nfs_verify_authflavors(struct nfs_parsed_mount_data *args,
> goto out;
>
> if (flavor == RPC_AUTH_NULL)
> - use_auth_null = true;
> + found_auth_null = true;
> }
>
> - if (use_auth_null) {
> - flavor = RPC_AUTH_NULL;
> + if (found_auth_null) {
> + flavor = args->auth_info.flavors[0];
> goto out;
> }
>
>
> --
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--
Chuck Lever
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