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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Jakub Sitnicki <jakub@cloudflare.com>,
	Lorenz Bauer <lmb@cloudflare.com>,
	Petar Penkov <ppenkov@google.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Sasha Levin <sashal@kernel.org>,
	netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH AUTOSEL 5.2 40/94] flow_dissector: Fix potential use-after-free on BPF_PROG_DETACH
Date: Wed,  4 Sep 2019 11:56:45 -0400	[thread overview]
Message-ID: <20190904155739.2816-40-sashal@kernel.org> (raw)
In-Reply-To: <20190904155739.2816-1-sashal@kernel.org>

From: Jakub Sitnicki <jakub@cloudflare.com>

[ Upstream commit db38de39684dda2bf307f41797db2831deba64e9 ]

Call to bpf_prog_put(), with help of call_rcu(), queues an RCU-callback to
free the program once a grace period has elapsed. The callback can run
together with new RCU readers that started after the last grace period.
New RCU readers can potentially see the "old" to-be-freed or already-freed
pointer to the program object before the RCU update-side NULLs it.

Reorder the operations so that the RCU update-side resets the protected
pointer before the end of the grace period after which the program will be
freed.

Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook")
Reported-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Petar Penkov <ppenkov@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/flow_dissector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index edd622956083d..b15c0c0f6e557 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -138,8 +138,8 @@ int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
 		mutex_unlock(&flow_dissector_mutex);
 		return -ENOENT;
 	}
-	bpf_prog_put(attached);
 	RCU_INIT_POINTER(net->flow_dissector_prog, NULL);
+	bpf_prog_put(attached);
 	mutex_unlock(&flow_dissector_mutex);
 	return 0;
 }
-- 
2.20.1


  parent reply	other threads:[~2019-09-04 16:18 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-04 15:56 [PATCH AUTOSEL 5.2 01/94] ieee802154: hwsim: Fix error handle path in hwsim_init_module Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 10/94] s390/bpf: fix lcgr instruction encoding Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 17/94] s390/bpf: use 32-bit index for tail calls Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 19/94] selftests/bpf: fix "bind{4, 6} deny specific IP & port" on s390 Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 20/94] tools: bpftool: close prog FD before exit on showing a single program Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 30/94] xdp: unpin xdp umem pages in error path Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 31/94] selftests/bpf: fix test_cgroup_storage on s390 Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 32/94] selftests/bpf: add config fragment BPF_JIT Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 33/94] selftests/bpf: install files test_xdp_vlan.sh Sasha Levin
2019-09-04 15:56 ` Sasha Levin [this message]
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 41/94] bpf: fix use after free in prog symbol exposure Sasha Levin
2019-09-04 15:56 ` [PATCH AUTOSEL 5.2 42/94] bpf: allow narrow loads of some sk_reuseport_md fields with offset > 0 Sasha Levin

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