2580d3f400
xfrm_bydst_resize() calls synchronize_rcu() while holding
hash_resize_mutex. But then on PREEMPT_RT configurations,
xfrm_policy_lookup_bytype() may acquire that mutex while running in an
RCU read side critical section. This results in a deadlock.
In fact the scope of hash_resize_mutex is way beyond the purpose of
xfrm_policy_lookup_bytype() to just fetch a coherent and stable policy
for a given destination/direction, along with other details.
The lower level net->xfrm.xfrm_policy_lock, which among other things
protects per destination/direction references to policy entries, is
enough to serialize and benefit from priority inheritance against the
write side. As a bonus, it makes it officially a per network namespace
synchronization business where a policy table resize on namespace A
shouldn't block a policy lookup on namespace B.
Fixes:
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|---|---|---|
| .. | ||
| espintcp.c | ||
| Kconfig | ||
| Makefile | ||
| xfrm_algo.c | ||
| xfrm_compat.c | ||
| xfrm_device.c | ||
| xfrm_hash.c | ||
| xfrm_hash.h | ||
| xfrm_inout.h | ||
| xfrm_input.c | ||
| xfrm_interface.c | ||
| xfrm_ipcomp.c | ||
| xfrm_output.c | ||
| xfrm_policy.c | ||
| xfrm_proc.c | ||
| xfrm_replay.c | ||
| xfrm_state.c | ||
| xfrm_sysctl.c | ||
| xfrm_user.c | ||