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ovpn injects decrypted packets into the netdev RX path through
ovpn_netdev_write() which invokes gro_cells_receive() and
dev_dstats_rx_add().
ovpn_netdev_write() is normally called in softirq context,
however, in case of TCP connections it may also be invoked
process context.
When this happens gro_cells_receive() will throw a warning:
[ 230.183747][ T12] WARNING: net/core/gro_cells.c:30 at gro_cells_receive+0x708/0xaa0, CPU#1: kworker/u16:0/12
and lockdep will also report a potential inconsistent lock state:
WARNING: inconsistent lock state
7.0.0-rc4+ #246 Tainted: G W
--------------------------------
inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
because attempts to acquire gro_cells->bh_lock by both
contexts may lead to a deadlock.
At the same time, dev_dstats_rx_add() does not expect to race
with a softirq (which may happen when invoked in process context),
because the latter may access its per-cpu state and corrupt
it.
Fix all this by invoking local_bh_disable/enable() around
gro_cells_receive() and dev_dstats_rx_add() to ensure that
bottom halves are always disabled before calling both of
them.
Fixes: 11851cbd60 ("ovpn: implement TCP transport")
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
Signed-off-by: Antonio Quartulli <antonio@openvpn.net>