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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:
|
||
|---|---|---|
| .. | ||
| bsd_comp.c | ||
| Kconfig | ||
| Makefile | ||
| ppp_async.c | ||
| ppp_deflate.c | ||
| ppp_generic.c | ||
| ppp_mppe.c | ||
| ppp_mppe.h | ||
| ppp_synctty.c | ||
| pppoe.c | ||
| pppox.c | ||
| pptp.c | ||