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() - dropped trace_svc_process() changes - context fixes in svc_process_common() Signed-off-by: Vasily Averin vvs@virtuozzo.com --- include/linux/sunrpc/svc.h | 5 ++++- net/sunrpc/svc.c | 10 +++++++--- net/sunrpc/svc_xprt.c | 5 +++-- net/sunrpc/svcsock.c | 2 +- 4 files changed, 15 insertions(+), 7 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index cc0fc712bb82..a8ac3f25b4ec 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -290,9 +290,12 @@ 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/net/sunrpc/svc.c b/net/sunrpc/svc.c index c5b0cb4f4056..6d521174427b 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -1062,6 +1062,8 @@ 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. */ @@ -1091,7 +1093,8 @@ 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);
@@ -1138,7 +1141,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv) case SVC_DENIED: goto err_bad_auth; case SVC_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); case SVC_DROP: goto dropit; @@ -1360,10 +1364,10 @@ 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 71f15da72f02..2b8e80c721db 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -454,10 +454,11 @@ 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 9701fcca002c..0a9fe033132c 100644 --- a/net/sunrpc/svcsock.c +++ b/net/sunrpc/svcsock.c @@ -1240,7 +1240,7 @@ 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];