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netgraph(4): Don't process NGQF_MESG items in NET_EPOCH context.

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Netgraph has two main types of message items:

- NGQF_DATA items are used for data processing. This is a hot path that
should be called from a NET_EPOCH context.

- NGQF_MESG items are used for node configuration. There are many places
in netgraph(4) where processing the NGQF_MESG item can call sections of code
that are forbidden in the NET_EPOCH context.

All item types can be queued and then processed using ngthread().
But ngthread() is unconditionally enter in the NET_EPOCH section for all types.
This causes panic/deadlocks when processing NGQF_MESG elements.

Reported by:	mjg
Reviewed by:	glebius, vmaffione (mentor)
Tested by:	mjg, afedorov
Approved by:	glebius, vmaffione (mentor)
Sponsored by:	vstack.com
Differential Revision:	https://reviews.freebsd.org/D36496
This commit is contained in:
Aleksandr Fedorov 2022-09-13 17:15:23 +03:00
parent bb1d472d79
commit 0e6e2c4ef3
1 changed files with 13 additions and 1 deletions
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14
sys/netgraph/ng_base.c
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@ -3439,7 +3439,19 @@ ngthread(void *arg)
} else {
NG_QUEUE_UNLOCK(&node->nd_input_queue);
NGI_GET_NODE(item, node); /* zaps stored node */
ng_apply_item(node, item, rw);
if ((item->el_flags & NGQF_TYPE) == NGQF_MESG) {
/*
* NGQF_MESG items should never be processed in
* NET_EPOCH context. So, temporary exit from EPOCH.
*/
NET_EPOCH_EXIT(et);
ng_apply_item(node, item, rw);
NET_EPOCH_ENTER(et);
} else {
ng_apply_item(node, item, rw);
}
NG_NODE_UNREF(node);
}
}