Patch "skbuff: only inherit relevant tx_flags" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

skbuff: only inherit relevant tx_flags

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
skbuff-only-inherit-relevant-tx_flags.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Willem de Bruijn <[email protected]>
Date: Thu, 8 Jun 2017 11:35:03 -0400
Subject: skbuff: only inherit relevant tx_flags

From: Willem de Bruijn <[email protected]>

[ 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.

---
 net/core/skbuff.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

@@ -2551,7 +2551,8 @@ void skb_split(struct sk_buff *skb, stru
 {
 	int pos = skb_headlen(skb);
 
-	skb_shinfo(skb1)->tx_flags = skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;
+	skb_shinfo(skb1)->tx_flags |= 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_bu
 		skb_copy_from_linear_data_offset(head_skb, offset,
 						 skb_put(nskb, hsize), hsize);
 
-		skb_shinfo(nskb)->tx_flags = skb_shinfo(head_skb)->tx_flags &
-			SKBTX_SHARED_FRAG;
+		skb_shinfo(nskb)->tx_flags |= skb_shinfo(head_skb)->tx_flags &
+					      SKBTX_SHARED_FRAG;
 
 		while (pos < offset + len) {
 			if (i >= nfrags) {

@@ -3734,7 +3735,8 @@ void __skb_tstamp_tx(struct sk_buff *ori
 		return;
 
 	if (tsonly) {
-		skb_shinfo(skb)->tx_flags = skb_shinfo(orig_skb)->tx_flags;
+		skb_shinfo(skb)->tx_flags |= skb_shinfo(orig_skb)->tx_flags &
+					     SKBTX_ANY_TSTAMP;
 		skb_shinfo(skb)->tskey = skb_shinfo(orig_skb)->tskey;
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/skbuff-only-inherit-relevant-tx_flags.patch