rpc: fix NULL dereference on kmalloc failure

[ Upstream commit 0ddc942394013f08992fc379ca04cffacbbe3dae ]

I think this is unlikely but possible:

svc_authenticate sets rq_authop and calls svcauth_gss_accept.  The
kmalloc(sizeof(*svcdata), GFP_KERNEL) fails, leaving rq_auth_data NULL,
and returning SVC_DENIED.

This causes svc_process_common to go to err_bad_auth, and eventually
call svc_authorise.  That calls ->release == svcauth_gss_release, which
tries to dereference rq_auth_data.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Link: https://lore.kernel.org/linux-nfs/3F1B347F-B809-478F-A1E9-0BE98E22B0F0@oracle.com/T/#t
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index fd897d900d123e65b38447279fdbc30c285e4480..85ad23d9a8a9b19ad19aba874b5ca611820815d2 100644 (file)
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -1705,11 +1705,14 @@ static int
 svcauth_gss_release(struct svc_rqst *rqstp)
 {
        struct gss_svc_data *gsd = (struct gss_svc_data *)rqstp->rq_auth_data;
-       struct rpc_gss_wire_cred *gc = &gsd->clcred;
+       struct rpc_gss_wire_cred *gc;
        struct xdr_buf *resbuf = &rqstp->rq_res;
        int stat = -EINVAL;
        struct sunrpc_net *sn = net_generic(SVC_NET(rqstp), sunrpc_net_id);
 
+       if (!gsd)
+               goto out;
+       gc = &gsd->clcred;
        if (gc->gc_proc != RPC_GSS_PROC_DATA)
                goto out;
        /* Release can be called twice, but we only wrap once. */
@@ -1750,10 +1753,10 @@ out_err:
        if (rqstp->rq_cred.cr_group_info)
                put_group_info(rqstp->rq_cred.cr_group_info);
        rqstp->rq_cred.cr_group_info = NULL;
-       if (gsd->rsci)
+       if (gsd && gsd->rsci) {
                cache_put(&gsd->rsci->h, sn->rsc_cache);
-       gsd->rsci = NULL;
-
+               gsd->rsci = NULL;
+       }
        return stat;
 }