diff options
| author | Jakub Kicinski <kuba@kernel.org> | 2025-12-06 17:09:41 -0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-12-10 01:15:27 -0800 |
| commit | 006a5035b495dec008805df249f92c22c89c3d2e (patch) | |
| tree | 28ec392e8b2177b26cca538b1bbbab2fe658d5e1 /include | |
| parent | 1231eec6994be29d6bb5c303dfa54731ed9fc0e6 (diff) | |
inet: frags: flush pending skbs in fqdir_pre_exit()
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/inet_frag.h | 13 | ||||
| -rw-r--r-- | include/net/ipv6_frag.h | 9 |
2 files changed, 7 insertions, 15 deletions
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index 3ffaceee7bbc..365925c9d262 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 38ef66826939..41d9fc6965f9 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; |