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Message-Id: <20251013-rq_bvec-v6-1-17982fc64ad2@kernel.org>
Date: Mon, 13 Oct 2025 09:38:23 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Chuck Lever <chuck.lever@...cle.com>, NeilBrown <neil@...wn.name>,
Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>,
Tom Talpey <tom@...pey.com>, Trond Myklebust <trondmy@...nel.org>,
Anna Schumaker <anna@...nel.org>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
David Howells <dhowells@...hat.com>
Cc: Brandon Adams <brandona@...a.com>, linux-nfs@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v6] sunrpc: allocate a separate bvec array for socket sends
svc_tcp_sendmsg() calls xdr_buf_to_bvec() with the second slot of
rq_bvec as the start, but doesn't reduce the array length by one, which
could lead to an array overrun. Also, rq_bvec is always rq_maxpages in
length, which can be too short in some cases, since the TCP record
marker consumes a slot.
Fix both problems by adding a separate bvec array to the svc_sock that
is specifically for sending. For TCP, make this array one slot longer
than rq_maxpages, to account for the record marker. For UDP, only
allocate as large an array as we need since it's limited to 64k of
payload.
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
Another update based on Neil's feedback. This version allocates the
array when the socket is allocated, and fixes the UDP length
calculation.
---
Changes in v6:
- allocate sk_bvec in ->xpo_create
- fix the array-length calculation for UDP
- Link to v5: https://lore.kernel.org/r/20251010-rq_bvec-v5-1-44976250199d@kernel.org
Changes in v5:
- reduce the size of sk_bvec on UDP sockets
- Link to v4: https://lore.kernel.org/r/20251010-rq_bvec-v4-1-627567f1ce91@kernel.org
Changes in v4:
- switch to allocating a separate bvec for sends in the svc_sock
- Link to v3: https://lore.kernel.org/r/20251009-rq_bvec-v3-0-57181360b9cb@kernel.org
Changes in v3:
- Add rq_bvec_len field and use it in appropriate places
- Link to v2: https://lore.kernel.org/r/20251008-rq_bvec-v2-0-823c0a85a27c@kernel.org
Changes in v2:
- Better changelog message for patch #2
- Link to v1: https://lore.kernel.org/r/20251008-rq_bvec-v1-0-7f23d32d75e5@kernel.org
---
include/linux/sunrpc/svcsock.h | 3 +++
net/sunrpc/svcsock.c | 54 ++++++++++++++++++++++++++++++++++++------
2 files changed, 50 insertions(+), 7 deletions(-)
diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index 963bbe251e52109a902f6b9097b6e9c3c23b1fd8..de37069aba90899be19b1090e6e90e509a3cf530 100644
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -26,6 +26,9 @@ struct svc_sock {
void (*sk_odata)(struct sock *);
void (*sk_owspace)(struct sock *);
+ /* For sends (protected by xpt_mutex) */
+ struct bio_vec *sk_bvec;
+
/* private TCP part */
/* On-the-wire fragment header: */
__be32 sk_marker;
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 0cb9c4d457453b26db29f08985b056c3f8d59447..e979505a21b69267a10d39f9084b557db4c9369c 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -68,6 +68,16 @@
#define RPCDBG_FACILITY RPCDBG_SVCXPRT
+/*
+ * For UDP:
+ * 1 for header page
+ * 16 for up to 64kb of payload + 1 in case it's not aligned
+ * 1 for tail page
+ */
+enum {
+ SUNRPC_MAX_UDP_SENDPAGES = 1 + 16 + 1 + 1
+};
+
/* To-do: to avoid tying up an nfsd thread while waiting for a
* handshake request, the request could instead be deferred.
*/
@@ -740,14 +750,14 @@ static int svc_udp_sendto(struct svc_rqst *rqstp)
if (svc_xprt_is_dead(xprt))
goto out_notconn;
- count = xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, xdr);
+ count = xdr_buf_to_bvec(svsk->sk_bvec, SUNRPC_MAX_UDP_SENDPAGES, xdr);
- iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, svsk->sk_bvec,
count, rqstp->rq_res.len);
err = sock_sendmsg(svsk->sk_sock, &msg);
if (err == -ECONNREFUSED) {
/* ICMP error on earlier request. */
- iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, svsk->sk_bvec,
count, rqstp->rq_res.len);
err = sock_sendmsg(svsk->sk_sock, &msg);
}
@@ -1236,19 +1246,19 @@ static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp,
int ret;
/* The stream record marker is copied into a temporary page
- * fragment buffer so that it can be included in rq_bvec.
+ * fragment buffer so that it can be included in sk_bvec.
*/
buf = page_frag_alloc(&svsk->sk_frag_cache, sizeof(marker),
GFP_KERNEL);
if (!buf)
return -ENOMEM;
memcpy(buf, &marker, sizeof(marker));
- bvec_set_virt(rqstp->rq_bvec, buf, sizeof(marker));
+ bvec_set_virt(svsk->sk_bvec, buf, sizeof(marker));
- count = xdr_buf_to_bvec(rqstp->rq_bvec + 1, rqstp->rq_maxpages,
+ count = xdr_buf_to_bvec(svsk->sk_bvec + 1, rqstp->rq_maxpages,
&rqstp->rq_res);
- iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, svsk->sk_bvec,
1 + count, sizeof(marker) + rqstp->rq_res.len);
ret = sock_sendmsg(svsk->sk_sock, &msg);
page_frag_free(buf);
@@ -1393,6 +1403,20 @@ void svc_sock_update_bufs(struct svc_serv *serv)
spin_unlock_bh(&serv->sv_lock);
}
+static int svc_sock_sendpages(struct svc_serv *serv, struct socket *sock, int flags)
+{
+ switch (sock->type) {
+ case SOCK_STREAM:
+ /* +1 for TCP record marker */
+ if (flags & SVC_SOCK_TEMPORARY)
+ return svc_serv_maxpages(serv) + 1;
+ return 0;
+ case SOCK_DGRAM:
+ return SUNRPC_MAX_UDP_SENDPAGES;
+ }
+ return -EINVAL;
+}
+
/*
* Initialize socket for RPC use and create svc_sock struct
*/
@@ -1403,12 +1427,26 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
struct svc_sock *svsk;
struct sock *inet;
int pmap_register = !(flags & SVC_SOCK_ANONYMOUS);
+ int sendpages;
unsigned long pages;
+ sendpages = svc_sock_sendpages(serv, sock, flags);
+ if (sendpages < 0)
+ return ERR_PTR(sendpages);
+
pages = svc_serv_maxpages(serv);
svsk = kzalloc(struct_size(svsk, sk_pages, pages), GFP_KERNEL);
if (!svsk)
return ERR_PTR(-ENOMEM);
+
+ if (sendpages) {
+ svsk->sk_bvec = kcalloc(sendpages, sizeof(*svsk->sk_bvec), GFP_KERNEL);
+ if (!svsk->sk_bvec) {
+ kfree(svsk);
+ return ERR_PTR(-ENOMEM);
+ }
+ }
+
svsk->sk_maxpages = pages;
inet = sock->sk;
@@ -1420,6 +1458,7 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
inet->sk_protocol,
ntohs(inet_sk(inet)->inet_sport));
if (err < 0) {
+ kfree(svsk->sk_bvec);
kfree(svsk);
return ERR_PTR(err);
}
@@ -1637,5 +1676,6 @@ static void svc_sock_free(struct svc_xprt *xprt)
sock_release(sock);
page_frag_cache_drain(&svsk->sk_frag_cache);
+ kfree(svsk->sk_bvec);
kfree(svsk);
}
---
base-commit: 05d2192090744b16ce05bd221c459a9357c17525
change-id: 20251008-rq_bvec-b66afd0fdbbb
Best regards,
--
Jeff Layton <jlayton@...nel.org>
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