From: Jakub Kicinski kuba@kernel.org
commit fda6c89fe3d9aca073495a664e1d5aea28cd4377 upstream.
lianhui reports that when MPLS fails to register the sysctl table under new location (during device rename) the old pointers won't get overwritten and may be freed again (double free).
Handle this gracefully. The best option would be unregistering the MPLS from the device completely on failure, but unfortunately mpls_ifdown() can fail. So failing fully is also unreliable.
Another option is to register the new table first then only remove old one if the new one succeeds. That requires more code, changes order of notifications and two tables may be visible at the same time.
sysctl point is not used in the rest of the code - set to NULL on failures and skip unregister if already NULL.
Reported-by: lianhui tang bluetlh@gmail.com Fixes: 0fae3bf018d9 ("mpls: handle device renames for per-device sysctls") 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 --- net/mpls/af_mpls.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -1344,6 +1344,7 @@ static int mpls_dev_sysctl_register(stru free: kfree(table); out: + mdev->sysctl = NULL; return -ENOBUFS; }
@@ -1353,6 +1354,9 @@ static void mpls_dev_sysctl_unregister(s struct net *net = dev_net(dev); struct ctl_table *table;
+ if (!mdev->sysctl) + return; + table = mdev->sysctl->ctl_table_arg; unregister_net_sysctl_table(mdev->sysctl); kfree(table);