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authorGuillaume Nault <g.nault@alphalink.fr>2018-01-10 16:24:45 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-31 12:55:55 +0100
commit00f9e47c6f9d9d25e1bf9cd5f58652d74e36d567 (patch)
treee40eed5fe2401c5ccd12cb69190fcfa30d5fd936
parent260eb694b5a4bd3424a7c445128fb5a784e95e3d (diff)
ppp: unlock all_ppp_mutex before registering device
[ 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>
-rw-r--r--drivers/net/ppp/ppp_generic.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index b883af93929c..fc4c2ccc3d22 100644
--- 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 *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);