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tcp: fix for splice receive when used with software LRO
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If an skb has nr_frags set to zero but its frag_list is not empty (as
it can happen if software LRO is enabled), and a previous
tcp_read_sock has consumed the linear part of the skb, then
__skb_splice_bits:

(a) incorrectly reports an error and

(b) forgets to update the offset to account for the linear part

Any of the two problems will cause the subsequent __skb_splice_bits
call (the one that handles the frag_list skbs) to either skip data,
or, if the unadjusted offset is greater then the size of the next skb
in the frag_list, make tcp_splice_read loop forever.

Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Octavian Purdila authored and David S. Miller committed Jun 28, 2008
1 parent 57413eb commit db43a28
Showing 1 changed file with 12 additions and 5 deletions.
17 changes: 12 additions & 5 deletions net/core/skbuff.c
Original file line number Diff line number Diff line change
Expand Up @@ -1292,12 +1292,14 @@ static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
{
unsigned int nr_pages = spd->nr_pages;
unsigned int poff, plen, len, toff, tlen;
int headlen, seg;
int headlen, seg, error = 0;

toff = *offset;
tlen = *total_len;
if (!tlen)
if (!tlen) {
error = 1;
goto err;
}

/*
* if the offset is greater than the linear part, go directly to
Expand Down Expand Up @@ -1339,7 +1341,8 @@ static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
* just jump directly to update and return, no point
* in going over fragments when the output is full.
*/
if (spd_fill_page(spd, virt_to_page(p), plen, poff, skb))
error = spd_fill_page(spd, virt_to_page(p), plen, poff, skb);
if (error)
goto done;

tlen -= plen;
Expand Down Expand Up @@ -1369,7 +1372,8 @@ static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
if (!plen)
break;

if (spd_fill_page(spd, f->page, plen, poff, skb))
error = spd_fill_page(spd, f->page, plen, poff, skb);
if (error)
break;

tlen -= plen;
Expand All @@ -1382,7 +1386,10 @@ static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
return 0;
}
err:
return 1;
/* update the offset to reflect the linear part skip, if any */
if (!error)
*offset = toff;
return error;
}

/*
Expand Down

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