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authorJakub Sitnicki <jakub@cloudflare.com>2019-08-21 14:17:20 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2019-08-24 01:15:34 +0200
commitdb38de39684dda2bf307f41797db2831deba64e9 (patch)
treeaf5b19557c1fda37db52a3cb3ffcee646b59fb3b /net/core/flow_dissector.c
parentselftests/bpf: install files test_xdp_vlan.sh (diff)
downloadlinux-dev-db38de39684dda2bf307f41797db2831deba64e9.tar.xz
linux-dev-db38de39684dda2bf307f41797db2831deba64e9.zip
flow_dissector: Fix potential use-after-free on BPF_PROG_DETACH
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>
Diffstat (limited to 'net/core/flow_dissector.c')
-rw-r--r--net/core/flow_dissector.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 3e6fedb57bc1..2470b4b404e6 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -142,8 +142,8 @@ 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;
}