3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
commit 15fe076edea787807a7cdc168df832544b58eba6 upstream.
syzbot reported crashes [1] and provided a C repro easing bug hunting.
When/if packet_do_bind() calls __unregister_prot_hook() and releases po->bind_lock, another thread can run packet_notifier() and process an NETDEV_UP event.
This calls register_prot_hook() and hooks again the socket right before first thread is able to grab again po->bind_lock.
Fixes this issue by temporarily setting po->num to 0, as suggested by David Miller.
[1] dev_remove_pack: ffff8801bf16fa80 not found ------------[ cut here ]------------ kernel BUG at net/core/dev.c:7945! ( BUG_ON(!list_empty(&dev->ptype_all)); ) invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: device syz0 entered promiscuous mode CPU: 0 PID: 3161 Comm: syzkaller404108 Not tainted 4.14.0+ #190 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801cc57a500 task.stack: ffff8801cc588000 RIP: 0010:netdev_run_todo+0x772/0xae0 net/core/dev.c:7945 RSP: 0018:ffff8801cc58f598 EFLAGS: 00010293 RAX: ffff8801cc57a500 RBX: dffffc0000000000 RCX: ffffffff841f75b2 RDX: 0000000000000000 RSI: 1ffff100398b1ede RDI: ffff8801bf1f8810 device syz0 entered promiscuous mode RBP: ffff8801cc58f898 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801bf1f8cd8 R13: ffff8801cc58f870 R14: ffff8801bf1f8780 R15: ffff8801cc58f7f0 FS: 0000000001716880(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020b13000 CR3: 0000000005e25000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:106 tun_detach drivers/net/tun.c:670 [inline] tun_chr_close+0x49/0x60 drivers/net/tun.c:2845 __fput+0x333/0x7f0 fs/file_table.c:210 ____fput+0x15/0x20 fs/file_table.c:244 task_work_run+0x199/0x270 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x9bb/0x1ae0 kernel/exit.c:865 do_group_exit+0x149/0x400 kernel/exit.c:968 SYSC_exit_group kernel/exit.c:979 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:977 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x44ad19
Fixes: 30f7ea1c2b5f ("packet: race condition in packet_bind") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Francesco Ruggeri fruggeri@aristanetworks.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Ben Hutchings ben@decadent.org.uk --- net/packet/af_packet.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2732,6 +2732,10 @@ static int packet_do_bind(struct sock *s if (need_rehook) { if (po->running) { rcu_read_unlock(); + /* prevents packet_notifier() from calling + * register_prot_hook() + */ + po->num = 0; __unregister_prot_hook(sk, true); rcu_read_lock(); dev_curr = po->prot_hook.dev; @@ -2740,6 +2744,7 @@ static int packet_do_bind(struct sock *s dev->ifindex); }
+ BUG_ON(po->running); po->num = proto; po->prot_hook.type = proto;