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netfilter: xt_hashlimit: unregister proc file before releasing mutex 

Before releasing the global mutex, we only unlink the hashtable
from the hash list, its proc file is still not unregistered at
this point. So syzbot could trigger a race condition where a
parallel htable_create() could register the same file immediately
after the mutex is released.

Move htable_remove_proc_entry() back to mutex protection to
fix this. And, fold htable_destroy() into htable_put() to make
the code slightly easier to understand.

Reported-and-tested-by: syzbot+d195fd3b9a364ddd6731@syzkaller.appspotmail.com
Fixes: c4a3922d2d ("netfilter: xt_hashlimit: reduce hashlimit_mutex scope for htable_put()")
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Cong Wang 2020-02-12 22:53:52 -08:00 committed by Pablo Neira Ayuso
parent 0954df70fb
commit 99b79c3900
1 changed files with 6 additions and 10 deletions
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16
net/netfilter/xt_hashlimit.c
View File

@ -402,15 +402,6 @@ static void htable_remove_proc_entry(struct xt_hashlimit_htable *hinfo)
remove_proc_entry(hinfo->name, parent);
}
static void htable_destroy(struct xt_hashlimit_htable *hinfo)
{
cancel_delayed_work_sync(&hinfo->gc_work);
htable_remove_proc_entry(hinfo);
htable_selective_cleanup(hinfo, true);
kfree(hinfo->name);
vfree(hinfo);
}
static struct xt_hashlimit_htable *htable_find_get(struct net *net,
const char *name,
u_int8_t family)
@ -432,8 +423,13 @@ static void htable_put(struct xt_hashlimit_htable *hinfo)
{
if (refcount_dec_and_mutex_lock(&hinfo->use, &hashlimit_mutex)) {
hlist_del(&hinfo->node);
htable_remove_proc_entry(hinfo);
mutex_unlock(&hashlimit_mutex);
htable_destroy(hinfo);
cancel_delayed_work_sync(&hinfo->gc_work);
htable_selective_cleanup(hinfo, true);
kfree(hinfo->name);
vfree(hinfo);
}
}