Commit 0d5b9311 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

inet: frags: better deal with smp races 

Multiple cpus might attempt to insert a new fragment in rhashtable,
if for example RPS is buggy, as reported by 배석진 in
https://patchwork.ozlabs.org/patch/994601/



We use rhashtable_lookup_get_insert_key() instead of
rhashtable_insert_fast() to let cpus losing the race
free their own inet_frag_queue and use the one that
was inserted by another cpu.

Fixes: 648700f7 ("inet: frags: use rhashtables for reassembly units")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatar배석진 <soukjin.bae@samsung.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e12c2252

net/ipv4/inet_fragment.c

+15 −14
Original line number Diff line number Diff line
@@ -178,21 +178,22 @@ static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf, 
}



static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,

						void *arg)

						void *arg,

						struct inet_frag_queue **prev)

{

	struct inet_frags *f = nf->f;

	struct inet_frag_queue *q;

	int err;



	q = inet_frag_alloc(nf, f, arg);

	if (!q)

	if (!q) {

		*prev = ERR_PTR(-ENOMEM);

		return NULL;



	}

	mod_timer(&q->timer, jiffies + nf->timeout);



	err = rhashtable_insert_fast(&nf->rhashtable, &q->node,

				     f->rhash_params);

	if (err < 0) {

	*prev = rhashtable_lookup_get_insert_key(&nf->rhashtable, &q->key,

						 &q->node, f->rhash_params);

	if (*prev) {

		q->flags |= INET_FRAG_COMPLETE;

		inet_frag_kill(q);

		inet_frag_destroy(q);
@@ -204,22 +205,22 @@ static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf, 
/* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */

struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, void *key)

{

	struct inet_frag_queue *fq;

	struct inet_frag_queue *fq = NULL, *prev;



	if (!nf->high_thresh || frag_mem_limit(nf) > nf->high_thresh)

		return NULL;



	rcu_read_lock();



	fq = rhashtable_lookup(&nf->rhashtable, key, nf->f->rhash_params);

	if (fq) {

	prev = rhashtable_lookup(&nf->rhashtable, key, nf->f->rhash_params);

	if (!prev)

		fq = inet_frag_create(nf, key, &prev);

	if (prev && !IS_ERR(prev)) {

		fq = prev;

		if (!refcount_inc_not_zero(&fq->refcnt))

			fq = NULL;

		rcu_read_unlock();

		return fq;

	}

	rcu_read_unlock();



	return inet_frag_create(nf, key);

	return fq;

}

EXPORT_SYMBOL(inet_frag_find);

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