6.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jakub Kicinski kuba@kernel.org
[ Upstream commit 006a5035b495dec008805df249f92c22c89c3d2e ]
We have been seeing occasional deadlocks on pernet_ops_rwsem since September in NIPA. The stuck task was usually modprobe (often loading a driver like ipvlan), trying to take the lock as a Writer. lockdep does not track readers for rwsems so the read wasn't obvious from the reports.
On closer inspection the Reader holding the lock was conntrack looping forever in nf_conntrack_cleanup_net_list(). Based on past experience with occasional NIPA crashes I looked thru the tests which run before the crash and noticed that the crash follows ip_defrag.sh. An immediate red flag. Scouring thru (de)fragmentation queues reveals skbs sitting around, holding conntrack references.
The problem is that since conntrack depends on nf_defrag_ipv6, nf_defrag_ipv6 will load first. Since nf_defrag_ipv6 loads first its netns exit hooks run _after_ conntrack's netns exit hook.
Flush all fragment queue SKBs during fqdir_pre_exit() to release conntrack references before conntrack cleanup runs. Also flush the queues in timer expiry handlers when they discover fqdir->dead is set, in case packet sneaks in while we're running the pre_exit flush.
The commit under Fixes is not exactly the culprit, but I think previously the timer firing would eventually unblock the spinning conntrack.
Fixes: d5dd88794a13 ("inet: fix various use-after-free in defrags units") Reviewed-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/20251207010942.1672972-4-kuba@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/inet_frag.h | 13 +------------ include/net/ipv6_frag.h | 9 ++++++--- net/ipv4/inet_fragment.c | 36 ++++++++++++++++++++++++++++++++++++ net/ipv4/ip_fragment.c | 12 +++++++----- 4 files changed, 50 insertions(+), 20 deletions(-)
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index 3ffaceee7bbc0..365925c9d2628 100644 --- a/include/net/inet_frag.h +++ b/include/net/inet_frag.h @@ -123,18 +123,7 @@ void inet_frags_fini(struct inet_frags *);
int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net);
-static inline void fqdir_pre_exit(struct fqdir *fqdir) -{ - /* Prevent creation of new frags. - * Pairs with READ_ONCE() in inet_frag_find(). - */ - WRITE_ONCE(fqdir->high_thresh, 0); - - /* Pairs with READ_ONCE() in inet_frag_kill(), ip_expire() - * and ip6frag_expire_frag_queue(). - */ - WRITE_ONCE(fqdir->dead, true); -} +void fqdir_pre_exit(struct fqdir *fqdir); void fqdir_exit(struct fqdir *fqdir);
void inet_frag_kill(struct inet_frag_queue *q, int *refs); diff --git a/include/net/ipv6_frag.h b/include/net/ipv6_frag.h index 38ef66826939e..41d9fc6965f9a 100644 --- a/include/net/ipv6_frag.h +++ b/include/net/ipv6_frag.h @@ -69,9 +69,6 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq) int refs = 1;
rcu_read_lock(); - /* Paired with the WRITE_ONCE() in fqdir_pre_exit(). */ - if (READ_ONCE(fq->q.fqdir->dead)) - goto out_rcu_unlock; spin_lock(&fq->q.lock);
if (fq->q.flags & INET_FRAG_COMPLETE) @@ -80,6 +77,12 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq) fq->q.flags |= INET_FRAG_DROP; inet_frag_kill(&fq->q, &refs);
+ /* Paired with the WRITE_ONCE() in fqdir_pre_exit(). */ + if (READ_ONCE(fq->q.fqdir->dead)) { + inet_frag_queue_flush(&fq->q, 0); + goto out; + } + dev = dev_get_by_index_rcu(net, fq->iif); if (!dev) goto out; diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index 1bf969b5a1cb5..001ee5c4d962e 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -218,6 +218,41 @@ static int __init inet_frag_wq_init(void)
pure_initcall(inet_frag_wq_init);
+void fqdir_pre_exit(struct fqdir *fqdir) +{ + struct inet_frag_queue *fq; + struct rhashtable_iter hti; + + /* Prevent creation of new frags. + * Pairs with READ_ONCE() in inet_frag_find(). + */ + WRITE_ONCE(fqdir->high_thresh, 0); + + /* Pairs with READ_ONCE() in inet_frag_kill(), ip_expire() + * and ip6frag_expire_frag_queue(). + */ + WRITE_ONCE(fqdir->dead, true); + + rhashtable_walk_enter(&fqdir->rhashtable, &hti); + rhashtable_walk_start(&hti); + + while ((fq = rhashtable_walk_next(&hti))) { + if (IS_ERR(fq)) { + if (PTR_ERR(fq) != -EAGAIN) + break; + continue; + } + spin_lock_bh(&fq->lock); + if (!(fq->flags & INET_FRAG_COMPLETE)) + inet_frag_queue_flush(fq, 0); + spin_unlock_bh(&fq->lock); + } + + rhashtable_walk_stop(&hti); + rhashtable_walk_exit(&hti); +} +EXPORT_SYMBOL(fqdir_pre_exit); + void fqdir_exit(struct fqdir *fqdir) { INIT_WORK(&fqdir->destroy_work, fqdir_work_fn); @@ -290,6 +325,7 @@ void inet_frag_queue_flush(struct inet_frag_queue *q, { unsigned int sum;
+ reason = reason ?: SKB_DROP_REASON_FRAG_REASM_TIMEOUT; sum = inet_frag_rbtree_purge(&q->rb_fragments, reason); sub_frag_mem_limit(q->fqdir, sum); } diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 32f1c1a46ba72..56b0f738d2f27 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -134,11 +134,6 @@ static void ip_expire(struct timer_list *t) net = qp->q.fqdir->net;
rcu_read_lock(); - - /* Paired with WRITE_ONCE() in fqdir_pre_exit(). */ - if (READ_ONCE(qp->q.fqdir->dead)) - goto out_rcu_unlock; - spin_lock(&qp->q.lock);
if (qp->q.flags & INET_FRAG_COMPLETE) @@ -146,6 +141,13 @@ static void ip_expire(struct timer_list *t)
qp->q.flags |= INET_FRAG_DROP; inet_frag_kill(&qp->q, &refs); + + /* Paired with WRITE_ONCE() in fqdir_pre_exit(). */ + if (READ_ONCE(qp->q.fqdir->dead)) { + inet_frag_queue_flush(&qp->q, 0); + goto out; + } + __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); __IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);