From d35ac850410966010e92f401f4e21868a9ea4d8b Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 4 Jun 2025 12:01:10 -0400 Subject: [PATCH] nfsd: handle get_client_locked() failure in nfsd4_setclientid_confirm() commit 908e4ead7f757504d8b345452730636e298cbf68 upstream. Lei Lu recently reported that nfsd4_setclientid_confirm() did not check the return value from get_client_locked(). a SETCLIENTID_CONFIRM could race with a confirmed client expiring and fail to get a reference. That could later lead to a UAF. Fix this by getting a reference early in the case where there is an extant confirmed client. If that fails then treat it as if there were no confirmed client found at all. In the case where the unconfirmed client is expiring, just fail and return the result from get_client_locked(). Reported-by: lei lu Closes: https://lore.kernel.org/linux-nfs/CAEBF3_b=UvqzNKdnfD_52L05Mqrqui9vZ2eFamgAbV0WG+FNWQ@mail.gmail.com/ Fixes: d20c11d86d8f ("nfsd: Protect session creation and client confirm using client_lock") Cc: stable@vger.kernel.org Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/nfs4state.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index bf78745b19ca9..6cf7907805e13 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -4284,10 +4284,16 @@ nfsd4_setclientid_confirm(struct svc_rqst *rqstp, } status = nfs_ok; if (conf) { - old = unconf; - unhash_client_locked(old); - nfsd4_change_callback(conf, &unconf->cl_cb_conn); - } else { + if (get_client_locked(conf) == nfs_ok) { + old = unconf; + unhash_client_locked(old); + nfsd4_change_callback(conf, &unconf->cl_cb_conn); + } else { + conf = NULL; + } + } + + if (!conf) { old = find_confirmed_client_by_name(&unconf->cl_name, nn); if (old) { status = nfserr_clid_inuse; @@ -4304,10 +4310,14 @@ nfsd4_setclientid_confirm(struct svc_rqst *rqstp, } trace_nfsd_clid_replaced(&old->cl_clientid); } + status = get_client_locked(unconf); + if (status != nfs_ok) { + old = NULL; + goto out; + } move_to_confirmed(unconf); conf = unconf; } - get_client_locked(conf); spin_unlock(&nn->client_lock); if (conf == unconf) fsnotify_dentry(conf->cl_nfsd_info_dentry, FS_MODIFY); -- 2.47.3