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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Willem de Bruijn <willemb@google.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.4 141/167] skbuff: only inherit relevant
 tx_flags
Thread-Topic: [PATCH AUTOSEL for 4.4 141/167] skbuff: only inherit relevant
 tx_flags
Thread-Index: AQHTv5x/RojlwOv5vUGrGmqifSGUQA==
Date:   Mon, 19 Mar 2018 16:08:19 +0000
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From: Willem de Bruijn <willemb@google.com>

[ Upstream commit fff88030b3ff930ca7a3d74acfee0472f33887ea ]

When inheriting tx_flags from one skbuff to another, always apply a
mask to avoid overwriting unrelated other bits in the field.

The two SKBTX_SHARED_FRAG cases clears all other bits. In practice,
tx_flags are zero at this point now. But this is fragile. Timestamp
flags are set, for instance, if in tcp_gso_segment, after this clear
in skb_segment.

The SKBTX_ANY_TSTAMP mask in __skb_tstamp_tx ensures that new
skbs do not accidentally inherit flags such as SKBTX_SHARED_FRAG.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 net/core/skbuff.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 02f0a705ee96..620dc871f7de 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2551,7 +2551,8 @@ void skb_split(struct sk_buff *skb, struct sk_buff *s=
kb1, const u32 len)
 {
 	int pos =3D skb_headlen(skb);
=20
-	skb_shinfo(skb1)->tx_flags =3D skb_shinfo(skb)->tx_flags & SKBTX_SHARED_F=
RAG;
+	skb_shinfo(skb1)->tx_flags |=3D skb_shinfo(skb)->tx_flags &
+				      SKBTX_SHARED_FRAG;
 	if (len < pos)	/* Split line is inside header. */
 		skb_split_inside_header(skb, skb1, len, pos);
 	else		/* Second chunk has no header, nothing to copy. */
@@ -3115,8 +3116,8 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 		skb_copy_from_linear_data_offset(head_skb, offset,
 						 skb_put(nskb, hsize), hsize);
=20
-		skb_shinfo(nskb)->tx_flags =3D skb_shinfo(head_skb)->tx_flags &
-			SKBTX_SHARED_FRAG;
+		skb_shinfo(nskb)->tx_flags |=3D skb_shinfo(head_skb)->tx_flags &
+					      SKBTX_SHARED_FRAG;
=20
 		while (pos < offset + len) {
 			if (i >=3D nfrags) {
@@ -3734,7 +3735,8 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
 		return;
=20
 	if (tsonly) {
-		skb_shinfo(skb)->tx_flags =3D skb_shinfo(orig_skb)->tx_flags;
+		skb_shinfo(skb)->tx_flags |=3D skb_shinfo(orig_skb)->tx_flags &
+					     SKBTX_ANY_TSTAMP;
 		skb_shinfo(skb)->tskey =3D skb_shinfo(orig_skb)->tskey;
 	}
=20
--=20
2.14.1