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ppp: unlock all_ppp_mutex before registering device

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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: 8cb775bc0a ("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>
This commit is contained in:
Guillaume Nault 2018-01-10 16:24:45 +01:00 committed by David S. Miller
parent 66940f35d5
commit 0171c41835
1 changed files with 3 additions and 2 deletions
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5
drivers/net/ppp/ppp_generic.c
View file

@ -1006,17 +1006,18 @@ static int ppp_unit_register(struct ppp *ppp, int unit, bool ifname_is_set)
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);