From 9f782db3f5ceee9aa8de6f853969fbec1b8c6e65 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ilpo=20J=C3=A4rvinen?= Date: Tue, 25 Nov 2008 13:57:01 -0800 Subject: [PATCH] tcp: skb_shift cannot cache frag ptrs past pskb_expand_head MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Since pskb_expand_head creates copy of the shared area we cannot keep any frag ptr past de-cloning. This fixes the tcpdump recvfrom -EFAULT problem. Signed-off-by: Ilpo Järvinen Signed-off-by: David S. Miller --- net/core/skbuff.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 57555a4525da..e03d77d4c1c9 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2018,7 +2018,10 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len) skb_split_no_header(skb, skb1, len, pos); } -/* Shifting from/to a cloned skb is a no-go. */ +/* Shifting from/to a cloned skb is a no-go. + * + * Caller cannot keep skb_shinfo related pointers past calling here! + */ static int skb_prepare_for_shift(struct sk_buff *skb) { return skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC); @@ -2070,6 +2073,8 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen) skb_prepare_for_shift(tgt)) return 0; + /* All previous frag pointers might be stale! */ + fragfrom = &skb_shinfo(skb)->frags[from]; fragto = &skb_shinfo(tgt)->frags[merge]; fragto->size += shiftlen; -- 2.30.2