5.4-stable review patch. If anyone has any objections, please let me know.
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From: Jeff Layton jlayton@kernel.org
[ Upstream commit 908e4ead7f757504d8b345452730636e298cbf68 ]
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 llfamsec@gmail.com Closes: https://lore.kernel.org/linux-nfs/CAEBF3_b=UvqzNKdnfD_52L05Mqrqui9vZ2eFamgAb... Fixes: d20c11d86d8f ("nfsd: Protect session creation and client confirm using client_lock") Cc: stable@vger.kernel.org Signed-off-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com [ Adjust context ] Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/nfsd/nfs4state.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)
--- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -3956,10 +3956,16 @@ nfsd4_setclientid_confirm(struct svc_rqs } status = nfs_ok; if (conf) { /* case 1: callback update */ - old = unconf; - unhash_client_locked(old); - nfsd4_change_callback(conf, &unconf->cl_cb_conn); - } else { /* case 3: normal case; new or rebooted client */ + 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) { /* case 3: normal case; new or rebooted client */ old = find_confirmed_client_by_name(&unconf->cl_name, nn); if (old) { status = nfserr_clid_inuse; @@ -3975,10 +3981,14 @@ nfsd4_setclientid_confirm(struct svc_rqs goto out; } } + 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); nfsd4_probe_callback(conf); spin_lock(&nn->client_lock);