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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: 648700f76b ("inet: frags: use rhashtables for reassembly units")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: 배석진 <soukjin.bae@samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-11-08 17:34:27 -08:00 committed by David S. Miller
parent e12c225258
commit 0d5b9311ba
1 changed files with 15 additions and 14 deletions
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29
net/ipv4/inet_fragment.c
View File

@ -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);
}
EXPORT_SYMBOL(inet_frag_find);