sfc: extend the locking on mcdi->seqno

BugLink: https://bugs.launchpad.net/bugs/1966057
[ Upstream commit f1fb205efb0ccca55626fd4ef38570dd16b44719 ]

seqno could be read as a stale value outside of the lock. The lock is
already acquired to protect the modification of seqno against a possible
race condition. Place the reading of this value also inside this locking
to protect it against a possible race condition.

Signed-off-by: Niels Dossche <dossche.niels@gmail.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c
index be6bfd6b7ec7576407f85ebb786eaed238f7d8be..50baf62b2cbc6808bad368e45d6e2efce7573f8c 100644 (file)
--- a/drivers/net/ethernet/sfc/mcdi.c
+++ b/drivers/net/ethernet/sfc/mcdi.c
@@ -163,9 +163,9 @@ static void efx_mcdi_send_request(struct efx_nic *efx, unsigned cmd,
        /* Serialise with efx_mcdi_ev_cpl() and efx_mcdi_ev_death() */
        spin_lock_bh(&mcdi->iface_lock);
        ++mcdi->seqno;
+       seqno = mcdi->seqno & SEQ_MASK;
        spin_unlock_bh(&mcdi->iface_lock);
 
-       seqno = mcdi->seqno & SEQ_MASK;
        xflags = 0;
        if (mcdi->mode == MCDI_MODE_EVENTS)
                xflags |= MCDI_HEADER_XFLAGS_EVREQ;