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nfsd: never defer requests during idmap lookup

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During v4 request compound arg decoding, some ops (e.g. SETATTR)
can trigger idmap lookup upcalls. When those upcall responses get
delayed beyond the allowed time limit, cache_check() will mark the
request for deferral and cause it to be dropped.

This prevents nfs4svc_encode_compoundres from being executed, and
thus the session slot flag NFSD4_SLOT_INUSE never gets cleared.
Subsequent client requests will fail with NFSERR_JUKEBOX, given
that the slot will be marked as in-use, making the SEQUENCE op
fail.

Fix this by making sure that the RQ_USEDEFERRAL flag is always
clear during nfs4svc_decode_compoundargs(), since no v4 request
should ever be deferred.

Fixes: 2f425878b6 ("nfsd: don't use the deferral service, return NFS4ERR_DELAY")
Signed-off-by: Anthony Iliopoulos <ailiop@suse.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Anthony Iliopoulos 2025-12-22 14:30:04 -05:00 committed by Chuck Lever
parent 9abb354922
commit f9c206cdc4
3 changed files with 58 additions and 8 deletions
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48
fs/nfsd/nfs4idmap.c
View File

@ -643,13 +643,31 @@ static __be32 encode_name_from_id(struct xdr_stream *xdr,
return idmap_id_to_name(xdr, rqstp, type, id);
}
__be32
nfsd_map_name_to_uid(struct svc_rqst *rqstp, const char *name, size_t namelen,
kuid_t *uid)
/**
* nfsd_map_name_to_uid - Map user@domain to local UID
* @rqstp: RPC execution context
* @name: user@domain name to be mapped
* @namelen: length of name, in bytes
* @uid: OUT: mapped local UID value
*
* Returns nfs_ok on success or an NFSv4 status code on failure.
*/
__be32 nfsd_map_name_to_uid(struct svc_rqst *rqstp, const char *name,
size_t namelen, kuid_t *uid)
{
__be32 status;
u32 id = -1;
/*
* The idmap lookup below triggers an upcall that invokes
* cache_check(). RQ_USEDEFERRAL must be clear to prevent
* cache_check() from setting RQ_DROPME via svc_defer().
* NFSv4 servers are not permitted to drop requests. Also
* RQ_DROPME will force NFSv4.1 session slot processing to
* be skipped.
*/
WARN_ON_ONCE(test_bit(RQ_USEDEFERRAL, &rqstp->rq_flags));
if (name == NULL || namelen == 0)
return nfserr_inval;
@ -660,13 +678,31 @@ nfsd_map_name_to_uid(struct svc_rqst *rqstp, const char *name, size_t namelen,
return status;
}
__be32
nfsd_map_name_to_gid(struct svc_rqst *rqstp, const char *name, size_t namelen,
kgid_t *gid)
/**
* nfsd_map_name_to_gid - Map user@domain to local GID
* @rqstp: RPC execution context
* @name: user@domain name to be mapped
* @namelen: length of name, in bytes
* @gid: OUT: mapped local GID value
*
* Returns nfs_ok on success or an NFSv4 status code on failure.
*/
__be32 nfsd_map_name_to_gid(struct svc_rqst *rqstp, const char *name,
size_t namelen, kgid_t *gid)
{
__be32 status;
u32 id = -1;
/*
* The idmap lookup below triggers an upcall that invokes
* cache_check(). RQ_USEDEFERRAL must be clear to prevent
* cache_check() from setting RQ_DROPME via svc_defer().
* NFSv4 servers are not permitted to drop requests. Also
* RQ_DROPME will force NFSv4.1 session slot processing to
* be skipped.
*/
WARN_ON_ONCE(test_bit(RQ_USEDEFERRAL, &rqstp->rq_flags));
if (name == NULL || namelen == 0)
return nfserr_inval;

2
fs/nfsd/nfs4proc.c
View File

@ -3013,8 +3013,6 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
BUG_ON(cstate->replay_owner);
out:
cstate->status = status;
/* Reset deferral mechanism for RPC deferrals */
set_bit(RQ_USEDEFERRAL, &rqstp->rq_flags);
return rpc_success;
}

16
fs/nfsd/nfs4xdr.c
View File

@ -6013,6 +6013,22 @@ nfs4svc_decode_compoundargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
args->ops = args->iops;
args->rqstp = rqstp;
/*
* NFSv4 operation decoders can invoke svc cache lookups
* that trigger svc_defer() when RQ_USEDEFERRAL is set,
* setting RQ_DROPME. This creates two problems:
*
* 1. Non-idempotency: Compounds make it too hard to avoid
* problems if a request is deferred and replayed.
*
* 2. Session slot leakage (NFSv4.1+): If RQ_DROPME is set
* during decode but SEQUENCE executes successfully, the
* session slot will be marked INUSE. The request is then
* dropped before encoding, so the slot is never released,
* rendering it permanently unusable by the client.
*/
clear_bit(RQ_USEDEFERRAL, &rqstp->rq_flags);
return nfsd4_decode_compound(args);
}