Re: [PATCH v2 0/2] sunrpc: don't strip a uid's groups when the mountd group lookup fails

[Jeff Layton]

On Sat, 2026-08-15 at 03:19 +0500, Ameer Hamza wrote:
> On a server running rpc.mountd with --manage-gids, a transient
> name-service failure makes mountd answer the auth.unix.gid upcall
> with a zero-group reply, which the kernel installs as a valid
> positive entry.  Patch 1 records such replies as negative entries
> on the classic /proc channel, so the credential keeps the groups
> it already carries.  Patch 2 does the same for the netlink upcall,
> which has an explicit NEGATIVE flag the parser does not propagate.
> 
> One observation from reviewing the netlink path: in steady-state
> netlink-only operation, mountd currently receives no unix_gid
> upcalls, because unix_gid_upcall() still gates request generation
> on cache_listeners_exist(), which counts only classic-channel
> writers, and netlink-mode mountd opens no /proc channels.  A
> flagged reply reaches the parser today only via the 30-second
> post-close grace window, a concurrent classic-channel writer, or
> a direct SUNRPC_CMD_UNIX_GID_SET_REQS.  Patch 2 fixes the parser
> semantics ahead of that; making upcall generation netlink-aware
> needs a per-cache listener signal (mountd subscribes to the
> notification group even without --manage-gids) and is left for a
> separate, runtime-tested series.
> 

Do you intend to send the separate series for this?

> Patch 1 was tested on a live 6.12 server over NFSv3 and v4.0-v4.2
> with sec=sys and sec=krb5, and applies unmodified to every
> maintained stable tree, 5.10.y through 7.1.y.  Patch 2 is build-
> and static-checked (sparse, W=1) but not runtime-tested.
> 
> Changes since v1:
> - split the netlink fix into its own patch with its own Fixes:
>   tag, as requested by Chuck
> - patch 1 is unchanged
> 
> v1: https://lore.kernel.org/linux-nfs/20260814172507.1474519-1-ameer.hamza@xxxxxxxxxxx/
> 
> Ameer Hamza (2):
>   sunrpc: treat empty auth.unix.gid replies as negative entries
>   sunrpc: honor the netlink unix_gid NEGATIVE flag
> 
>  net/sunrpc/svcauth_unix.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> 
> base-commit: 46db3c8a1be96a354758b44b1d4fbb4b70d09a20

Good catch. Both of these look good to me.
-- 
Jeff Layton <jlayton@xxxxxxxxxx>