Messages in this thread | | | Date | Tue, 27 Jan 2009 12:16:42 +0000 | From | Jarek Poplawski <> | Subject | Re: [PATCH v3] tcp: splice as many packets as possible at once |
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On Tue, Jan 27, 2009 at 10:48:05PM +1100, Herbert Xu wrote: > On Tue, Jan 27, 2009 at 10:35:11AM +0000, Jarek Poplawski wrote: > > > > > > Yes, but ip_append_data() (and skb_append_datato_frags() for > > > > NETIF_F_UFO only, so currently not a problem), uses this differently, > > > > and these pages in sk->sk_sndmsg_page could leak or be used after > > > > kfree. (I didn't track locking in these other places). > > > > > > It'll be freed when the socket is freed so that should be fine. > > > > I don't think so: these places can overwrite sk->sk_sndmsg_page left > > after tcp_sendmsg(), or skb_splice_bits() now, with NULL or a new > > pointer without put_page() (they only reference copied chunks and > > expect auto freeing). On the other hand, if tcp_sendmsg() reads after > > them it could use a pointer after the page is freed, I guess. > > I wasn't referring to the first part of your sentence. That can't > happen because they're only used for UDP sockets, this is a TCP > socket.
Do you mean this part from ip_append_data() isn't used for TCP?:
1007 1008 if (page && (left = PAGE_SIZE - off) > 0) { 1009 if (copy >= left) 1010 copy = left; 1011 if (page != frag->page) { 1012 if (i == MAX_SKB_FRAGS) { 1013 err = -EMSGSIZE; 1014 goto error; 1015 } 1016 get_page(page); 1017 skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0); 1018 frag = &skb_shinfo(skb)->frags[i]; 1019 } 1020 } else if (i < MAX_SKB_FRAGS) { 1021 if (copy > PAGE_SIZE) 1022 copy = PAGE_SIZE; 1023 page = alloc_pages(sk->sk_allocation, 0); 1024 if (page == NULL) { 1025 err = -ENOMEM; 1026 goto error; 1027 } 1028 sk->sk_sndmsg_page = page; 1029 sk->sk_sndmsg_off = 0; 1030 1031 skb_fill_page_desc(skb, i, page, 0, 0); 1032 frag = &skb_shinfo(skb)->frags[i]; 1033 } else {
Jarek P.
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