linux/drivers/net/ppp
Tom Parkin c1787ffd0d ppp: fix refcount underflow on channel unbridge
When setting up a channel bridge, ppp_bridge_channels sets the
pch->bridge field before taking the associated reference on the bridge
file instance.

This opens up a refcount underflow bug if ppp_bridge_channels called
via. iotcl runs concurrently with ppp_unbridge_channels executing via.
file release.

The bug is triggered by ppp_bridge_channels taking the error path
through the 'err_unset' label.  In this scenario, pch->bridge is set,
but the reference on the bridged channel will not be taken because
the function errors out.  If ppp_unbridge_channels observes pch->bridge
before it is unset by the error path, it will erroneously drop the
reference on the bridged channel and cause a refcount underflow.

To avoid this, ensure that ppp_bridge_channels holds a reference on
each channel in advance of setting the bridge pointers.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Fixes: 4cf476ced4 ("ppp: add PPPIOCBRIDGECHAN and PPPIOCUNBRIDGECHAN ioctls")
Acked-by: Guillaume Nault <gnault@redhat.com>
Link: https://lore.kernel.org/r/20210107181315.3128-1-tparkin@katalix.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-01-08 19:21:06 -08:00
..
bsd_comp.c treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
Kconfig treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ppp_async.c ppp: Adjust indentation into ppp_async_input 2019-12-09 20:32:40 -08:00
ppp_deflate.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
ppp_generic.c ppp: fix refcount underflow on channel unbridge 2021-01-08 19:21:06 -08:00
ppp_mppe.c mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
ppp_mppe.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ppp_synctty.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
pppoe.c net: make ->{get,set}sockopt in proto_ops optional 2020-07-19 18:16:41 -07:00
pppox.c compat_ioctl: pppoe: fix PPPOEIOCSFWD handling 2019-07-30 14:42:13 -07:00
pptp.c net: make ->{get,set}sockopt in proto_ops optional 2020-07-19 18:16:41 -07:00