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net: dsa: restore error path of dsa_tree_change_tag_proto

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When the DSA_NOTIFIER_TAG_PROTO returns an error, the user space process
which initiated the protocol change exits the kernel processing while
still holding the rtnl_mutex. So any other process attempting to lock
the rtnl_mutex would deadlock after such event.

The error handling of DSA_NOTIFIER_TAG_PROTO was inadvertently changed
by the blamed commit, introducing this regression. We must still call
rtnl_unlock(), and we must still call DSA_NOTIFIER_TAG_PROTO for the old
protocol. The latter is due to the limiting design of notifier chains
for cross-chip operations, which don't have a built-in error recovery
mechanism - we should look into using notifier_call_chain_robust for that.

Fixes: dc452a471d ("net: dsa: introduce tagger-owned storage for private and shared data")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20220228141715.146485-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Vladimir Oltean 2022-02-28 16:17:15 +02:00 committed by Jakub Kicinski
parent 2e77551c61
commit 0b0e2ff103
1 changed files with 1 additions and 1 deletions
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2
net/dsa/dsa2.c
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@ -1261,7 +1261,7 @@ int dsa_tree_change_tag_proto(struct dsa_switch_tree *dst,
info.tag_ops = tag_ops;
err = dsa_tree_notify(dst, DSA_NOTIFIER_TAG_PROTO, &info);
if (err)
return err;
goto out_unlock;
err = dsa_tree_bind_tag_proto(dst, tag_ops);
if (err)