path: root/net/packet
diff options
authorEric Dumazet <edumazet@google.com>2017-11-28 08:03:30 -0800
committerDavid S. Miller <davem@davemloft.net>2017-11-28 11:13:30 -0500
commit15fe076edea787807a7cdc168df832544b58eba6 (patch)
treef99ff8dea7ba100c7cc636bf0f9ecadbca8eae5e /net/packet
parent57f015f5eccf25fd4a3336fe3cbbee920a8fba6f (diff)
net/packet: fix a race in packet_bind() and packet_notifier()
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>
Diffstat (limited to 'net/packet')
1 files changed, 5 insertions, 0 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 1b7bb9d9865e..da215e5c1399 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3091,6 +3091,10 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
if (need_rehook) {
if (po->running) {
+ /* prevents packet_notifier() from calling
+ * register_prot_hook()
+ */
+ po->num = 0;
__unregister_prot_hook(sk, true);
dev_curr = po->prot_hook.dev;
@@ -3099,6 +3103,7 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
+ BUG_ON(po->running);
po->num = proto;
po->prot_hook.type = proto;