| Message ID | Pine.LNX.4.64.0811252202550.14851@wrl-59.cs.helsinki.fi |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi> Date: Tue, 25 Nov 2008 22:08:06 +0200 (EET) > 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 <ilpo.jarvinen@helsinki.fi> Good catch. I think everyone mucking around with these sorts of things has made this error at least once or twice :) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 57555a4..133ecd6 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;
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 <ilpo.jarvinen@helsinki.fi> --- net/core/skbuff.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-)