On Mon, Jul 17, 2006 at 08:22:44AM -0700, Greg KH wrote: > > Ick, this doesn't apply to 2.6.17, care to rediff it? I don't trust > myself to get it correct :)
Oops, I thought I rediffed against 2.6.17, but it must've been something else. Here is a second attempt: [NET]: Update frag_list in pskb_trim When pskb_trim has to defer to ___pksb_trim to trim the frag_list part of the packet, the frag_list is not updated to reflect the trimming. This will usually work fine until you hit something that uses the packet length or tail from the frag_list. Examples include esp_output and ip_fragment. Another problem caused by this is that you can end up with a linear packet with a frag_list attached. It is possible to get away with this if we audit everything to make sure that they always consult skb->len before going down onto frag_list. In fact we can do the samething for the paged part as well to avoid copying the data area of the skb. For now though, let's do the conservative fix and update frag_list. Many thanks to Marco Berizzi for helping me to track down this bug. This 4-year old bug took 3 months to track down. Marco was very patient indeed :) Signed-off-by: Herbert Xu <[EMAIL PROTECTED]> Signed-off-by: David S. Miller <[EMAIL PROTECTED]> Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f8f2347..2c31bb0 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -967,15 +967,16 @@ #ifndef NET_SKB_PAD #define NET_SKB_PAD 16 #endif -extern int ___pskb_trim(struct sk_buff *skb, unsigned int len, int realloc); +extern int ___pskb_trim(struct sk_buff *skb, unsigned int len); static inline void __skb_trim(struct sk_buff *skb, unsigned int len) { - if (!skb->data_len) { - skb->len = len; - skb->tail = skb->data + len; - } else - ___pskb_trim(skb, len, 0); + if (unlikely(skb->data_len)) { + WARN_ON(1); + return; + } + skb->len = len; + skb->tail = skb->data + len; } /** @@ -985,6 +986,7 @@ static inline void __skb_trim(struct sk_ * * Cut the length of a buffer down by removing data from the tail. If * the buffer is already under the length specified it is not modified. + * The skb must be linear. */ static inline void skb_trim(struct sk_buff *skb, unsigned int len) { @@ -995,12 +997,10 @@ static inline void skb_trim(struct sk_bu static inline int __pskb_trim(struct sk_buff *skb, unsigned int len) { - if (!skb->data_len) { - skb->len = len; - skb->tail = skb->data+len; - return 0; - } - return ___pskb_trim(skb, len, 1); + if (skb->data_len) + return ___pskb_trim(skb, len); + __skb_trim(skb, len); + return 0; } static inline int pskb_trim(struct sk_buff *skb, unsigned int len) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index fb3770f..40f108e 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -250,11 +250,11 @@ nodata: } -static void skb_drop_fraglist(struct sk_buff *skb) +static void skb_drop_list(struct sk_buff **listp) { - struct sk_buff *list = skb_shinfo(skb)->frag_list; + struct sk_buff *list = *listp; - skb_shinfo(skb)->frag_list = NULL; + *listp = NULL; do { struct sk_buff *this = list; @@ -263,6 +263,11 @@ static void skb_drop_fraglist(struct sk_ } while (list); } +static inline void skb_drop_fraglist(struct sk_buff *skb) +{ + skb_drop_list(&skb_shinfo(skb)->frag_list); +} + static void skb_clone_fraglist(struct sk_buff *skb) { struct sk_buff *list; @@ -800,49 +805,80 @@ struct sk_buff *skb_pad(struct sk_buff * return nskb; } -/* Trims skb to length len. It can change skb pointers, if "realloc" is 1. - * If realloc==0 and trimming is impossible without change of data, - * it is BUG(). +/* Trims skb to length len. It can change skb pointers. */ -int ___pskb_trim(struct sk_buff *skb, unsigned int len, int realloc) +int ___pskb_trim(struct sk_buff *skb, unsigned int len) { + struct sk_buff **fragp; + struct sk_buff *frag; int offset = skb_headlen(skb); int nfrags = skb_shinfo(skb)->nr_frags; int i; + int err; + + if (skb_cloned(skb) && + unlikely((err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))) + return err; for (i = 0; i < nfrags; i++) { int end = offset + skb_shinfo(skb)->frags[i].size; - if (end > len) { - if (skb_cloned(skb)) { - BUG_ON(!realloc); - if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) - return -ENOMEM; - } - if (len <= offset) { - put_page(skb_shinfo(skb)->frags[i].page); - skb_shinfo(skb)->nr_frags--; - } else { - skb_shinfo(skb)->frags[i].size = len - offset; - } + + if (end < len) { + offset = end; + continue; + } + + if (len > offset) + skb_shinfo(skb)->frags[i++].size = len - offset; + + skb_shinfo(skb)->nr_frags = i; + + for (; i < nfrags; i++) + put_page(skb_shinfo(skb)->frags[i].page); + + if (skb_shinfo(skb)->frag_list) + skb_drop_fraglist(skb); + break; + } + + for (fragp = &skb_shinfo(skb)->frag_list; (frag = *fragp); + fragp = &frag->next) { + int end = offset + frag->len; + + if (skb_shared(frag)) { + struct sk_buff *nfrag; + + nfrag = skb_clone(frag, GFP_ATOMIC); + if (unlikely(!nfrag)) + return -ENOMEM; + + nfrag->next = frag->next; + frag = nfrag; + *fragp = frag; } - offset = end; + + if (end < len) { + offset = end; + continue; + } + + if (end > len && + unlikely((err = pskb_trim(frag, len - offset)))) + return err; + + if (frag->next) + skb_drop_list(&frag->next); + break; } - if (offset < len) { + if (len > skb_headlen(skb)) { skb->data_len -= skb->len - len; skb->len = len; } else { - if (len <= skb_headlen(skb)) { - skb->len = len; - skb->data_len = 0; - skb->tail = skb->data + len; - if (skb_shinfo(skb)->frag_list && !skb_cloned(skb)) - skb_drop_fraglist(skb); - } else { - skb->data_len -= skb->len - len; - skb->len = len; - } + skb->len = len; + skb->data_len = 0; + skb->tail = skb->data + len; } return 0; - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
