This is a note to let you know that I've just added the patch titled
net_sched: gen_estimator: fix lockdep splat
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: net_sched-gen_estimator-fix-lockdep-splat.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 40ca54e3a686f13117f3de0c443f8026dadf7c44 Mon Sep 17 00:00:00 2001
From: Eric Dumazet edumazet@google.com Date: Sat, 27 Jan 2018 10:58:43 -0800 Subject: net_sched: gen_estimator: fix lockdep splat
From: Eric Dumazet edumazet@google.com
commit 40ca54e3a686f13117f3de0c443f8026dadf7c44 upstream.
syzbot reported a lockdep splat in gen_new_estimator() / est_fetch_counters() when attempting to lock est->stats_lock.
Since est_fetch_counters() is called from BH context from timer interrupt, we need to block BH as well when calling it from process context.
Most qdiscs use per cpu counters and are immune to the problem, but net/sched/act_api.c and net/netfilter/xt_RATEEST.c are using a spinlock to protect their data. They both call gen_new_estimator() while object is created and not yet alive, so this bug could not trigger a deadlock, only a lockdep splat.
Fixes: 1c0d32fde5bd ("net_sched: gen_estimator: complete rewrite of rate estimators") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Acked-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/core/gen_estimator.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/net/core/gen_estimator.c +++ b/net/core/gen_estimator.c @@ -159,7 +159,11 @@ int gen_new_estimator(struct gnet_stats_ est->intvl_log = intvl_log; est->cpu_bstats = cpu_bstats;
+ if (stats_lock) + local_bh_disable(); est_fetch_counters(est, &b); + if (stats_lock) + local_bh_enable(); est->last_bytes = b.bytes; est->last_packets = b.packets; old = rcu_dereference_protected(*rate_est, 1);
Patches currently in stable-queue which might be from edumazet@google.com are
queue-4.15/net_sched-gen_estimator-fix-lockdep-splat.patch queue-4.15/tun-fix-tun_napi_alloc_frags-frag-allocator.patch queue-4.15/netfilter-x_tables-avoid-out-of-bounds-reads-in-xt_request_find_-match-target.patch queue-4.15/netfilter-xt_rateest-acquire-xt_rateest_mutex-for-hash-insert.patch