[PATCH stable, 6.1 0/2] Fix for sockmap causing data stalls

[PATCH stable, 6.1 0/2] Fix for sockmap causing data stalls

[John Fastabend]

The attached two patches fix an issue with running BPF sockmap on TCP
sockets where applications error out due to sender doing a send for
each scatter gather element in the msg. The other 6.x stable and
longterm kernels have this fix so we don't see it there and the issue
was introduced in 6.1 by converting to the read_skb() interface. The
5.15 stable kernels use the read_sock() interface which doesn't have
this issue.

We missed adding the fixes tag to the original series because the work
was a code improvement and wasn't originally identified as a bugfix.

The first patch applies cleanly, the second patch does not because
it touches smc, espintcp, and siw which do not apply because that
code does not use sendmsg() yet on 6.1. I remove those chunks of the
patch because they don't apply here.

I added a Fixes tag to the patches to point at the patch introducing
the issue. Originally I sent something similar to this as a single
patch where I incorrectly merged the two patches. Greg asked me to
do this as two patches. Thanks.

David Howells (2):
  tcp_bpf: Inline do_tcp_sendpages as it's now a wrapper around
    tcp_sendmsg
  tcp_bpf, smc, tls, espintcp, siw: Reduce MSG_SENDPAGE_NOTLAST usage

 net/ipv4/tcp_bpf.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

-- 
2.33.0

[PATCH stable, 6.1 1/2] tcp_bpf: Inline do_tcp_sendpages as it's now a wrapper around tcp_sendmsg

[John Fastabend]

From: David Howells <dhowells@redhat.com>

[ Upstream commit ebf2e8860eea66e2c4764316b80c6a5ee5f336ee ]

do_tcp_sendpages() is now just a small wrapper around tcp_sendmsg_locked(),
so inline it.  This is part of replacing ->sendpage() with a call to
sendmsg() with MSG_SPLICE_PAGES set.

Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: John Fastabend <john.fastabend@gmail.com>
cc: Jakub Sitnicki <jakub@cloudflare.com>
cc: David Ahern <dsahern@kernel.org>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/ipv4/tcp_bpf.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index f8037d142bb7..f3def363b971 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -90,11 +90,13 @@ static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
 {
 	bool apply = apply_bytes;
 	struct scatterlist *sge;
+	struct msghdr msghdr = { .msg_flags = flags | MSG_SPLICE_PAGES, };
 	struct page *page;
 	int size, ret = 0;
 	u32 off;
 
 	while (1) {
+		struct bio_vec bvec;
 		bool has_tx_ulp;
 
 		sge = sk_msg_elem(msg, msg->sg.start);
@@ -106,16 +108,18 @@ static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
 		tcp_rate_check_app_limited(sk);
 retry:
 		has_tx_ulp = tls_sw_has_ctx_tx(sk);
-		if (has_tx_ulp) {
-			flags |= MSG_SENDPAGE_NOPOLICY;
-			ret = kernel_sendpage_locked(sk,
-						     page, off, size, flags);
-		} else {
-			ret = do_tcp_sendpages(sk, page, off, size, flags);
-		}
+		if (has_tx_ulp)
+			msghdr.msg_flags |= MSG_SENDPAGE_NOPOLICY;
 
+		if (flags & MSG_SENDPAGE_NOTLAST)
+			msghdr.msg_flags |= MSG_MORE;
+
+		bvec_set_page(&bvec, page, size, off);
+		iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, size);
+		ret = tcp_sendmsg_locked(sk, &msghdr, size);
 		if (ret <= 0)
 			return ret;
+
 		if (apply)
 			apply_bytes -= ret;
 		msg->sg.size -= ret;
@@ -495,7 +499,7 @@ static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 	long timeo;
 	int flags;
 
-	/* Don't let internal do_tcp_sendpages() flags through */
+	/* Don't let internal sendpage flags through */
 	flags = (msg->msg_flags & ~MSG_SENDPAGE_DECRYPTED);
 	flags |= MSG_NO_SHARED_FRAGS;
 
-- 
2.33.0

Re: [PATCH stable, 6.1 1/2] tcp_bpf: Inline do_tcp_sendpages as it's now a wrapper around tcp_sendmsg

[Greg KH]

On Tue, May 07, 2024 at 10:47:56AM -0700, John Fastabend wrote:
> From: David Howells <dhowells@redhat.com>
> 
> [ Upstream commit ebf2e8860eea66e2c4764316b80c6a5ee5f336ee ]
> 
> do_tcp_sendpages() is now just a small wrapper around tcp_sendmsg_locked(),
> so inline it.  This is part of replacing ->sendpage() with a call to
> sendmsg() with MSG_SPLICE_PAGES set.
> 
> Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()")
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: John Fastabend <john.fastabend@gmail.com>
> cc: Jakub Sitnicki <jakub@cloudflare.com>
> cc: David Ahern <dsahern@kernel.org>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
>  net/ipv4/tcp_bpf.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)

You too need to sign off on a patch you forward to someone else, that's
what the DCO means :)

Please fix up and resend.

thanks,

greg k-h

[PATCH stable, 6.1 2/2] tcp_bpf, smc, tls, espintcp, siw: Reduce MSG_SENDPAGE_NOTLAST usage

[John Fastabend]

From: David Howells <dhowells@redhat.com>

[ Upstream commit f8dd95b29d7ef08c19ec9720564acf72243ddcf6]

As MSG_SENDPAGE_NOTLAST is being phased out along with sendpage(), don't
use it further in than the sendpage methods, but rather translate it to
MSG_MORE and use that instead.

Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
cc: Bernard Metzler <bmt@zurich.ibm.com>
cc: Jason Gunthorpe <jgg@ziepe.ca>
cc: Leon Romanovsky <leon@kernel.org>
cc: John Fastabend <john.fastabend@gmail.com>
cc: Jakub Sitnicki <jakub@cloudflare.com>
cc: David Ahern <dsahern@kernel.org>
cc: Karsten Graul <kgraul@linux.ibm.com>
cc: Wenjia Zhang <wenjia@linux.ibm.com>
cc: Jan Karcher <jaka@linux.ibm.com>
cc: "D. Wythe" <alibuda@linux.alibaba.com>
cc: Tony Lu <tonylu@linux.alibaba.com>
cc: Wen Gu <guwen@linux.alibaba.com>
cc: Boris Pismenny <borisp@nvidia.com>
cc: Steffen Klassert <steffen.klassert@secunet.com>
cc: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/r/20230623225513.2732256-2-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/ipv4/tcp_bpf.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index f3def363b971..cd6648aaf570 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -88,9 +88,9 @@ static int bpf_tcp_ingress(struct sock *sk, struct sk_psock *psock,
 static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
 			int flags, bool uncharge)
 {
+	struct msghdr msghdr = {};
 	bool apply = apply_bytes;
 	struct scatterlist *sge;
-	struct msghdr msghdr = { .msg_flags = flags | MSG_SPLICE_PAGES, };
 	struct page *page;
 	int size, ret = 0;
 	u32 off;
@@ -107,11 +107,12 @@ static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
 
 		tcp_rate_check_app_limited(sk);
 retry:
+		msghdr.msg_flags = flags | MSG_SPLICE_PAGES;
 		has_tx_ulp = tls_sw_has_ctx_tx(sk);
 		if (has_tx_ulp)
 			msghdr.msg_flags |= MSG_SENDPAGE_NOPOLICY;
 
-		if (flags & MSG_SENDPAGE_NOTLAST)
+		if (size < sge->length && msg->sg.start != msg->sg.end)
 			msghdr.msg_flags |= MSG_MORE;
 
 		bvec_set_page(&bvec, page, size, off);
-- 
2.33.0