Commit 7a474c36 authored Jan 04, 2019 by Florian Westphal Committed by Steffen Klassert Jan 09, 2019

xfrm: policy: increment xfrm_hash_generation on hash rebuild

Hash rebuild will re-set all the inexact entries, then re-insert them.
Lookups that can occur in parallel will therefore not find any policies.

This was safe when lookups were still guarded by rwlock.
After rcu-ification, lookups check the hash_generation seqcount to detect
when a hash resize takes place. Hash rebuild missed the needed increment.

Hash resizes and hash rebuilds cannot occur in parallel (both acquire
hash_resize_mutex), so just increment xfrm_hash_generation, like resize.

Fixes: a7c44247 ("xfrm: policy: make xfrm_policy_lookup_bytype lockless")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

parent 355b00d1

net/xfrm/xfrm_policy.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1235,6 +1235,7 @@ static void xfrm_hash_rebuild(struct work_struct *work)
		} while (read_seqretry(&net->xfrm.policy_hthresh.lock, seq));

		spin_lock_bh(&net->xfrm.xfrm_policy_lock);
		write_seqcount_begin(&xfrm_policy_hash_generation);

		/* make sure that we can insert the indirect policies again before
		* we start with destructive action.
		@@ -1334,6 +1335,7 @@ static void xfrm_hash_rebuild(struct work_struct *work)

		out_unlock:
		__xfrm_policy_inexact_flush(net);
		write_seqcount_end(&xfrm_policy_hash_generation);
		spin_unlock_bh(&net->xfrm.xfrm_policy_lock);

		mutex_unlock(&hash_resize_mutex);

Admin message