While running nfs/connectathon tests kernel NULL-pointer exception
has been observed due to races in svcsock.c.
Race is appear when kernel accepts connection by kernel_accept
(which creates new socket) and start queuing ingress packets
to new socket. This happens in ksoftirq context which could run
concurrently on a different core while new socket setup is not done yet.
The fix is to re-order socket user data init sequence and add
write/read barrier calls to be sure that we got proper values
for callback pointers before actually calling them.
Test results: nfs/connectathon reports '0' failed tests for about 200+ iterations.
Signed-off-by: Vadim Lomovtsev <vlomovts@redhat.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields <bfields@redhat.com>