Fix modification of the received skbuff in rxrpc_input_soft_acks() and a
potential incorrect access of the buffer in a fragmented UDP packet (the
packet would probably have to be deliberately pre-generated as fragmented)
when AF_RXRPC tries to extract the contents of the SACK table by copying
out the contents of the SACK table into a buffer before attempting to parse
AF_RXRPC assumes that it can just call skb_condense() and then validly
access the SACK table from skb->data and that it will be a flat buffer -
but skb_condense() can silently fail to do anything under some
circumstances.
Note that whilst rxrpc_input_soft_acks() should be able to parse extended
ACKs, the rest of AF_RXRPC doesn't currently support that.
Further, there's then no need to call skb_condense() in rxrpc_input_ack(),
so don't.
Fixes: d57a3a1516 ("rxrpc: Save last ACK's SACK table rather than marking txbufs")
Reported-by: Michael Bommarito <michael.bommarito@gmail.com>
Link: https://lore.kernel.org/r/20260513180907.2061972-1-michael.bommarito@gmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Eric Dumazet <edumazet@google.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
cc: stable@kernel.org
Link: https://patch.msgid.link/105362.1780573560@warthog.procyon.org.uk
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
333b6d5bb9