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authorJarek Poplawski <jarkao2@gmail.com>2009-01-19 17:03:56 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2009-02-17 09:46:29 -0800
commitfa6872f58301c00e7e5bf075673b4b3b65dd151d (patch)
tree710759fcef6b054c1b47fddd52d55b443a4bc235 /Documentation/x86
parentc6d0986f9ebbae82005f083adf46d9146939eaf6 (diff)
net: Fix data corruption when splicing from sockets.
[ Upstream commit 8b9d3728977760f6bd1317c4420890f73695354e ] The trick in socket splicing where we try to convert the skb->data into a page based reference using virt_to_page() does not work so well. The idea is to pass the virt_to_page() reference via the pipe buffer, and refcount the buffer using a SKB reference. But if we are splicing from a socket to a socket (via sendpage) this doesn't work. The from side processing will grab the page (and SKB) references. The sendpage() calls will grab page references only, return, and then the from side processing completes and drops the SKB ref. The page based reference to skb->data is not enough to keep the kmalloc() buffer backing it from being reused. Yet, that is all that the socket send side has at this point. This leads to data corruption if the skb->data buffer is reused by SLAB before the send side socket actually gets the TX packet out to the device. The fix employed here is to simply allocate a page and copy the skb->data bytes into that page. This will hurt performance, but there is no clear way to fix this properly without a copy at the present time, and it is important to get rid of the data corruption. With fixes from Herbert Xu. Tested-by: Willy Tarreau <w@1wt.eu> Foreseen-by: Changli Gao <xiaosuo@gmail.com> Diagnosed-by: Willy Tarreau <w@1wt.eu> Reported-by: Willy Tarreau <w@1wt.eu> Fixed-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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