[Devel] [PATCH RH8 7/7] tcp: use sendpage_ok() to detect misused .sendpage

[Andrey Zhadchenko]

From: Coly Li <colyli at suse.de>

commit a10674bf2406 ("tcp: detecting the misuse of .sendpage for Slab
objects") adds the checks for Slab pages, but the pages don't have
page_count are still missing from the check.

Network layer's sendpage method is not designed to send page_count 0
pages neither, therefore both PageSlab() and page_count() should be
both checked for the sending page. This is exactly what sendpage_ok()
does.

This patch uses sendpage_ok() in do_tcp_sendpages() to detect misused
.sendpage, to make the code more robust.

Fixes: a10674bf2406 ("tcp: detecting the misuse of .sendpage for Slab objects")
Suggested-by: Eric Dumazet <eric.dumazet at gmail.com>
Signed-off-by: Coly Li <colyli at suse.de>
Cc: Vasily Averin <vvs at virtuozzo.com>
Cc: David S. Miller <davem at davemloft.net>
Cc: stable at vger.kernel.org
Signed-off-by: David S. Miller <davem at davemloft.net>

(cherry-picked from ms cf83a17edeeb ("tcp: use sendpage_ok() to detect misused .sendpage"))
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 538d63c..f8dbf6f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -962,7 +962,8 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
 	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"))
+	    WARN_ONCE(!sendpage_ok(page),
+		      "page must not be a Slab one and have page_count > 0"))
 		return -EINVAL;
 
 	/* Wait for a connection to finish. One exception is TCP Fast Open
-- 
1.8.3.1