From d7426c69a1942b2b9b709bf66b944ff09f561484 Mon Sep 17 00:00:00 2001 From: WANG Cong Date: Wed, 8 Feb 2017 10:02:13 -0800 Subject: [PATCH] sit: fix a double free on error path Dmitry reported a double free in sit_init_net(): kernel BUG at mm/percpu.c:689! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 0 PID: 15692 Comm: syz-executor1 Not tainted 4.10.0-rc6-next-20170206 #1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801c9cc27c0 task.stack: ffff88017d1d8000 RIP: 0010:pcpu_free_area+0x68b/0x810 mm/percpu.c:689 RSP: 0018:ffff88017d1df488 EFLAGS: 00010046 RAX: 0000000000010000 RBX: 00000000000007c0 RCX: ffffc90002829000 RDX: 0000000000010000 RSI: ffffffff81940efb RDI: ffff8801db841d94 RBP: ffff88017d1df590 R08: dffffc0000000000 R09: 1ffffffff0bb3bdd R10: dffffc0000000000 R11: 00000000000135dd R12: ffff8801db841d80 R13: 0000000000038e40 R14: 00000000000007c0 R15: 00000000000007c0 FS: 00007f6ea608f700(0000) GS:ffff8801dbe00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000002000aff8 CR3: 00000001c8d44000 CR4: 00000000001426f0 DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: free_percpu+0x212/0x520 mm/percpu.c:1264 ipip6_dev_free+0x43/0x60 net/ipv6/sit.c:1335 sit_init_net+0x3cb/0xa10 net/ipv6/sit.c:1831 ops_init+0x10a/0x530 net/core/net_namespace.c:115 setup_net+0x2ed/0x690 net/core/net_namespace.c:291 copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396 create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106 unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205 SYSC_unshare kernel/fork.c:2281 [inline] SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231 entry_SYSCALL_64_fastpath+0x1f/0xc2 This is because when tunnel->dst_cache init fails, we free dev->tstats once in ipip6_tunnel_init() and twice in sit_init_net(). This looks redundant but its ndo_uinit() does not seem enough to clean up everything here. So avoid this by setting dev->tstats to NULL after the first free, at least for -net. Reported-by: Dmitry Vyukov Signed-off-by: Cong Wang Signed-off-by: David S. Miller --- net/ipv6/sit.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index fad992ad4bc8..99853c6e33a8 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -1380,6 +1380,7 @@ static int ipip6_tunnel_init(struct net_device *dev) err = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL); if (err) { free_percpu(dev->tstats); + dev->tstats = NULL; return err; } -- 2.30.2