netdev - [bpf-next PATCH v3 03/18] net: do_tcp_sendpages flag to avoid SKBTX_SHARED

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sun, 18 Mar 2018 12:57:00 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     davejwatson@...com, davem@...emloft.net, daniel@...earbox.net,
        ast@...nel.org
Cc:     netdev@...r.kernel.org
Subject: [bpf-next PATCH v3 03/18] net: do_tcp_sendpages flag to avoid
 SKBTX_SHARED_FRAG

When calling do_tcp_sendpages() from in kernel and we know the data
has no references from user side we can omit SKBTX_SHARED_FRAG flag.
This patch adds an internal flag, NO_SKBTX_SHARED_FRAG that can be used
to omit setting SKBTX_SHARED_FRAG.

The flag is not exposed to userspace because the sendpage call from
the splice logic masks out all bits except MSG_MORE.

Signed-off-by: John Fastabend <john.fastabend@...il.com>
Acked-by: David S. Miller <davem@...emloft.net>
---
 include/linux/socket.h |    1 +
 net/ipv4/tcp.c         |    4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 1ce1f76..60e0148 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -287,6 +287,7 @@ struct ucred {
 #define MSG_SENDPAGE_NOTLAST 0x20000 /* sendpage() internal : not the last page */
 #define MSG_BATCH	0x40000 /* sendmmsg(): more messages coming */
 #define MSG_EOF         MSG_FIN
+#define MSG_NO_SHARED_FRAGS 0x80000 /* sendpage() internal : page frags are not shared */
 
 #define MSG_ZEROCOPY	0x4000000	/* Use user data in kernel path */
 #define MSG_FASTOPEN	0x20000000	/* Send data in TCP SYN */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index fb350f7..f90ec24 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -994,7 +994,9 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
 			get_page(page);
 			skb_fill_page_desc(skb, i, page, offset, copy);
 		}
-		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
+
+		if (!(flags & MSG_NO_SHARED_FRAGS))
+			skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 
 		skb->len += copy;
 		skb->data_len += copy;