tree 85e98e25e14f87bfa37e3ef3f8e73a2dda2c05a3
parent 09c45065257b5b194e08a1b4749daeebb961675e
author Jakub Kicinski <kuba@kernel.org> 1598470806 -0700
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1599913135 +0200

net: disable netpoll on fresh napis

[ Upstream commit 96e97bc07e90f175a8980a22827faf702ca4cb30 ]

napi_disable() makes sure to set the NAPI_STATE_NPSVC bit to prevent
netpoll from accessing rings before init is complete. However, the
same is not done for fresh napi instances in netif_napi_add(),
even though we expect NAPI instances to be added as disabled.

This causes crashes during driver reconfiguration (enabling XDP,
changing the channel count) - if there is any printk() after
netif_napi_add() but before napi_enable().

To ensure memory ordering is correct we need to use RCU accessors.

Reported-by: Rob Sherwood <rsher@fb.com>
Fixes: 2d8bff12699a ("netpoll: Close race condition between poll_one_napi and napi_disable")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>