Commit d4b09acf authored by Vasily Averin's avatar Vasily Averin Committed by J. Bruce Fields

sunrpc: use-after-free in svc_process_common()

if node have NFSv41+ mounts inside several net namespaces
it can lead to use-after-free in svc_process_common()

        /* Setup reply header */
        rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr(rqstp); <<< HERE

svc_process_common() can use incorrect rqstp->rq_xprt,
its caller function bc_svc_process() takes it from serv->sv_bc_xprt.
The problem is that serv is global structure but sv_bc_xprt
is assigned per-netnamespace.

According to Trond, the whole "let's set up rqstp->rq_xprt
for the back channel" is nothing but a giant hack in order
to work around the fact that svc_process_common() uses it
to find the xpt_ops, and perform a couple of (meaningless
for the back channel) tests of xpt_flags.

All we really need in svc_process_common() is to be able to run

Bruce J Fields points that this xpo_prep_reply_hdr() call
is an awfully roundabout way just to do "svc_putnl(resv, 0);"
in the tcp case.

This patch does not initialiuze rqstp->rq_xprt in bc_svc_process(),
now it calls svc_process_common() with rqstp->rq_xprt = NULL.

To adjust reply header svc_process_common() just check
rqstp->rq_prot and calls svc_tcp_prep_reply_hdr() for tcp case.

To handle rqstp->rq_xprt = NULL case in functions called from
svc_process_common() patch intruduces net namespace pointer
svc_rqst->rq_bc_net and adjust SVC_NET() definition.
Some other function was also adopted to properly handle described case.
Signed-off-by: default avatarVasily Averin <>
Fixes: 23c20ecd ("NFS: callback up - users counting cleanup")
Signed-off-by: default avatarJ. Bruce Fields <>
parent b8be5674
......@@ -295,9 +295,12 @@ struct svc_rqst {
struct svc_cacherep * rq_cacherep; /* cache info */
struct task_struct *rq_task; /* service thread */
spinlock_t rq_lock; /* per-request lock */
struct net *rq_bc_net; /* pointer to backchannel's
* net namespace
#define SVC_NET(svc_rqst) (svc_rqst->rq_xprt->xpt_net)
#define SVC_NET(rqst) (rqst->rq_xprt ? rqst->rq_xprt->xpt_net : rqst->rq_bc_net)
* Rigorous type checking on sockaddr type conversions
......@@ -569,7 +569,8 @@ TRACE_EVENT(svc_process,
__field(u32, vers)
__field(u32, proc)
__string(service, name)
__string(addr, rqst->rq_xprt->xpt_remotebuf)
__string(addr, rqst->rq_xprt ?
rqst->rq_xprt->xpt_remotebuf : "(null)")
......@@ -577,7 +578,8 @@ TRACE_EVENT(svc_process,
__entry->vers = rqst->rq_vers;
__entry->proc = rqst->rq_proc;
__assign_str(service, name);
__assign_str(addr, rqst->rq_xprt->xpt_remotebuf);
__assign_str(addr, rqst->rq_xprt ?
rqst->rq_xprt->xpt_remotebuf : "(null)");
TP_printk("addr=%s xid=0x%08x service=%s vers=%u proc=%u",
......@@ -1172,7 +1172,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
clear_bit(RQ_DROPME, &rqstp->rq_flags);
/* Setup reply header */
if (rqstp->rq_prot == IPPROTO_TCP)
svc_putu32(resv, rqstp->rq_xid);
......@@ -1244,7 +1245,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
* for lower versions. RPC_PROG_MISMATCH seems to be the closest
* fit.
if (versp->vs_need_cong_ctrl &&
if (versp->vs_need_cong_ctrl && rqstp->rq_xprt &&
!test_bit(XPT_CONG_CTRL, &rqstp->rq_xprt->xpt_flags))
goto err_bad_vers;
......@@ -1336,7 +1337,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
return 0;
if (test_bit(XPT_TEMP, &rqstp->rq_xprt->xpt_flags))
if (rqstp->rq_xprt && test_bit(XPT_TEMP, &rqstp->rq_xprt->xpt_flags))
dprintk("svc: svc_process close\n");
return 0;
......@@ -1459,10 +1460,10 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req,
dprintk("svc: %s(%p)\n", __func__, req);
/* Build the svc_rqst used by the common processing routine */
rqstp->rq_xprt = serv->sv_bc_xprt;
rqstp->rq_xid = req->rq_xid;
rqstp->rq_prot = req->rq_xprt->prot;
rqstp->rq_server = serv;
rqstp->rq_bc_net = req->rq_xprt->xprt_net;
rqstp->rq_addrlen = sizeof(req->rq_xprt->addr);
memcpy(&rqstp->rq_addr, &req->rq_xprt->addr, rqstp->rq_addrlen);
......@@ -468,10 +468,11 @@ static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
void svc_reserve(struct svc_rqst *rqstp, int space)
struct svc_xprt *xprt = rqstp->rq_xprt;
space += rqstp->rq_res.head[0].iov_len;
if (space < rqstp->rq_reserved) {
struct svc_xprt *xprt = rqstp->rq_xprt;
if (xprt && space < rqstp->rq_reserved) {
atomic_sub((rqstp->rq_reserved - space), &xprt->xpt_reserved);
rqstp->rq_reserved = space;
......@@ -1173,7 +1173,7 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
* Setup response header. TCP has a 4B record length field.
static void svc_tcp_prep_reply_hdr(struct svc_rqst *rqstp)
void svc_tcp_prep_reply_hdr(struct svc_rqst *rqstp)
struct kvec *resv = &rqstp->rq_res.head[0];
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