4.9-stable review patch. If anyone has any objections, please let me know.
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From: Guillaume Nault g.nault@alphalink.fr
[ Upstream commit 0171c41835591e9aa2e384b703ef9a6ae367c610 ]
ppp_dev_uninit(), which is the .ndo_uninit() handler of PPP devices, needs to lock pn->all_ppp_mutex. Therefore we mustn't call register_netdevice() with pn->all_ppp_mutex already locked, or we'd deadlock in case register_netdevice() fails and calls .ndo_uninit().
Fortunately, we can unlock pn->all_ppp_mutex before calling register_netdevice(). This lock protects pn->units_idr, which isn't used in the device registration process.
However, keeping pn->all_ppp_mutex locked during device registration did ensure that no device in transient state would be published in pn->units_idr. In practice, unlocking it before calling register_netdevice() doesn't change this property: ppp_unit_register() is called with 'ppp_mutex' locked and all searches done in pn->units_idr hold this lock too.
Fixes: 8cb775bc0a34 ("ppp: fix device unregistration upon netns deletion") Reported-and-tested-by: syzbot+367889b9c9e279219175@syzkaller.appspotmail.com Signed-off-by: Guillaume Nault g.nault@alphalink.fr Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ppp/ppp_generic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -1002,17 +1002,18 @@ static int ppp_unit_register(struct ppp if (!ifname_is_set) snprintf(ppp->dev->name, IFNAMSIZ, "ppp%i", ppp->file.index);
+ mutex_unlock(&pn->all_ppp_mutex); + ret = register_netdevice(ppp->dev); if (ret < 0) goto err_unit;
atomic_inc(&ppp_unit_count);
- mutex_unlock(&pn->all_ppp_mutex); - return 0;
err_unit: + mutex_lock(&pn->all_ppp_mutex); unit_put(&pn->units_idr, ppp->file.index); err: mutex_unlock(&pn->all_ppp_mutex);