tree 803d92cada2f9062417d4b6038482689b0c86f84
parent 385910f2b275a636238f70844f1b6da9fda6f2da
author Herbert Xu <herbert@gondor.apana.org.au> 1145391854 -0700
committer David S. Miller <davem@sunset.davemloft.net> 1145401069 -0700

[TCP]: Fix truesize underflow

There is a problem with the TSO packet trimming code.  The cause of
this lies in the tcp_fragment() function.

When we allocate a fragment for a completely non-linear packet the
truesize is calculated for a payload length of zero.  This means that
truesize could in fact be less than the real payload length.

When that happens the TSO packet trimming can cause truesize to become
negative.  This in turn can cause sk_forward_alloc to be -n * PAGE_SIZE
which would trigger the warning.

I've copied the code DaveM used in tso_fragment which should work here.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>