netdev - [PATCH] tcp: detecting the misuse of .sendpage for Slab objects

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Date:   Wed, 6 Mar 2019 14:10:22 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org
Subject: [PATCH] tcp: detecting the misuse of .sendpage for Slab objects

sendpage was not designed for processing of the Slab pages,
in some situations it can trigger BUG_ON on receiving side.

Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
---
 net/ipv4/tcp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ad07dd71063d..dbb08140cdc9 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -943,6 +943,10 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
 	ssize_t copied;
 	long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
 
+	if (IS_ENABLED(CONFIG_DEBUG_VM) &&
+	    WARN_ONCE(PageSlab(page), "page must not be a Slab one"))
+		return -EINVAL;
+
 	/* Wait for a connection to finish. One exception is TCP Fast Open
 	 * (passive side) where data is allowed to be sent before a connection
 	 * is fully established.
-- 
2.17.1