Backported mainline commit d4b09acf924b84bae77cad090a9d108e70b43643 Author: Vasily Averin vvs@virtuozzo.com Date: Mon Dec 24 14:44:52 2018 +0300

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()

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 rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr()

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: Vasily Averin vvs@virtuozzo.com Cc: stable@vger.kernel.org Fixes: 23c20ecd4475 ("NFS: callback up - users counting cleanup") Signed-off-by: J. Bruce Fields bfields@redhat.com

v2: added lost extern svc_tcp_prep_reply_hdr() Signed-off-by: Vasily Averin vvs@virtuozzo.com --- include/linux/sunrpc/svc.h | 5 ++++- include/trace/events/sunrpc.h | 6 ++++-- net/sunrpc/svc.c | 11 +++++++---- net/sunrpc/svc_xprt.c | 5 +++-- net/sunrpc/svcsock.c | 2 +- 5 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 73e130a840ce..fdb6b317d974 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -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 diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h index bbb08a3ef5cc..a2644c494a9c 100644 --- a/include/trace/events/sunrpc.h +++ b/include/trace/events/sunrpc.h @@ -582,7 +582,8 @@ 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)") ),

TP_fast_assign( @@ -590,7 +591,8 @@ 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", diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c index d13e05f1a990..d65f8d35de87 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -1144,6 +1144,8 @@ void svc_printk(struct svc_rqst *rqstp, const char *fmt, ...) static __printf(2,3) void svc_printk(struct svc_rqst *rqstp, const char *fmt, ...) {} #endif

+extern void svc_tcp_prep_reply_hdr(struct svc_rqst *); + /* * Common routine for processing the RPC request. */ @@ -1172,7 +1174,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv) clear_bit(RQ_DROPME, &rqstp->rq_flags);

/* Setup reply header */ - rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr(rqstp); + if (rqstp->rq_prot == IPPROTO_TCP) + svc_tcp_prep_reply_hdr(rqstp);

svc_putu32(resv, rqstp->rq_xid);

@@ -1244,7 +1247,7 @@ 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 +1339,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv) return 0;

close: - if (test_bit(XPT_TEMP, &rqstp->rq_xprt->xpt_flags)) + if (rqstp->rq_xprt && test_bit(XPT_TEMP, &rqstp->rq_xprt->xpt_flags)) svc_close_xprt(rqstp->rq_xprt); dprintk("svc: svc_process close\n"); return 0; @@ -1459,10 +1462,10 @@ 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); diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 83ccd0221c98..6cf0fd37cbf0 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -469,10 +469,11 @@ 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;

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c index fc1c0d9ef57d..97a8282955a8 100644 --- a/net/sunrpc/svcsock.c +++ b/net/sunrpc/svcsock.c @@ -1198,7 +1198,7 @@ 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];