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Date: Mon, 7 Mar 2022 10:18:58 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Ido Schimmel <idosch@...sch.org>, Vladimir Oltean <vladimir.oltean@....com>, Jakub Kicinski <kuba@...nel.org> Subject: [PATCH 4.9 32/32] net: dcb: disable softirqs in dcbnl_flush_dev() From: Vladimir Oltean <vladimir.oltean@....com> commit 10b6bb62ae1a49ee818fc479cf57b8900176773e upstream. Ido Schimmel points out that since commit 52cff74eef5d ("dcbnl : Disable software interrupts before taking dcb_lock"), the DCB API can be called by drivers from softirq context. One such in-tree example is the chelsio cxgb4 driver: dcb_rpl -> cxgb4_dcb_handle_fw_update -> dcb_ieee_setapp If the firmware for this driver happened to send an event which resulted in a call to dcb_ieee_setapp() at the exact same time as another DCB-enabled interface was unregistering on the same CPU, the softirq would deadlock, because the interrupted process was already holding the dcb_lock in dcbnl_flush_dev(). Fix this unlikely event by using spin_lock_bh() in dcbnl_flush_dev() as in the rest of the dcbnl code. Fixes: 91b0383fef06 ("net: dcb: flush lingering app table entries for unregistered devices") Reported-by: Ido Schimmel <idosch@...sch.org> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com> Link: https://lore.kernel.org/r/20220302193939.1368823-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski <kuba@...nel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- net/dcb/dcbnl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/net/dcb/dcbnl.c +++ b/net/dcb/dcbnl.c @@ -1942,7 +1942,7 @@ static void dcbnl_flush_dev(struct net_d { struct dcb_app_type *itr, *tmp; - spin_lock(&dcb_lock); + spin_lock_bh(&dcb_lock); list_for_each_entry_safe(itr, tmp, &dcb_app_list, list) { if (itr->ifindex == dev->ifindex) { @@ -1951,7 +1951,7 @@ static void dcbnl_flush_dev(struct net_d } } - spin_unlock(&dcb_lock); + spin_unlock_bh(&dcb_lock); } static int dcbnl_netdevice_event(struct notifier_block *nb,
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