Re: [PATCH net-next] tcp: highest_sack fix

From: Eric Dumazet <redacted>
Date: Tue, 14 Nov 2017 21:02:19 -0800

From: Eric Dumazet <edumazet@google.com>

syzbot easily found a regression added in our latest patches [1]

No longer set tp->highest_sack to the head of the send queue since
this is not logical and error prone.

Only sack processing should maintain the pointer to an skb from rtx queue.

We might in the future only remember the sequence instead of a pointer to skb,
since rb-tree should allow a fast lookup.

 ...

Fixes: 737ff314563c ("tcp: use sequence distance to detect reordering")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <redacted>
Reported-by: syzbot <redacted>

Applied.