net: dsa: fix unbalanced dsa_switch_tree reference counting
authorNikita Yushchenko <nikita.yoush@cogentembedded.com>
Mon, 28 Nov 2016 06:48:48 +0000 (09:48 +0300)
committerDavid S. Miller <davem@davemloft.net>
Mon, 28 Nov 2016 21:15:45 +0000 (16:15 -0500)
commit7a99cd6e213685b78118382e6a8fed506c82ccb2
treef08b04e49d5002be5dcee747fe5b91b0eb112ef7
parent79dc7e3f1cd323be4c81aa1a94faa1b3ed987fb2
net: dsa: fix unbalanced dsa_switch_tree reference counting

_dsa_register_switch() gets a dsa_switch_tree object either via
dsa_get_dst() or via dsa_add_dst(). Former path does not increase kref
in returned object (resulting into caller not owning a reference),
while later path does create a new object (resulting into caller owning
a reference).

The rest of _dsa_register_switch() assumes that it owns a reference, and
calls dsa_put_dst().

This causes a memory breakage if first switch in the tree initialized
successfully, but second failed to initialize. In particular, freed
dsa_swith_tree object is left referenced by switch that was initialized,
and later access to sysfs attributes of that switch cause OOPS.

To fix, need to add kref_get() call to dsa_get_dst().

Fixes: 83c0afaec7b7 ("net: dsa: Add new binding implementation")
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/dsa/dsa2.c