From 93636d1f1f162ae89ae4f2a22a83bf4fd960724e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 2 Nov 2016 20:21:20 -0700 Subject: [PATCH] netlink: netlink_diag_dump() runs without locks A recent commit removed locking from netlink_diag_dump() but forgot one error case. ===================================== [ BUG: bad unlock balance detected! ] 4.9.0-rc3+ #336 Not tainted ------------------------------------- syz-executor/4018 is trying to release lock ([ 36.220068] nl_table_lock ) at: [] netlink_diag_dump+0x1a3/0x250 net/netlink/diag.c:182 but there are no more locks to release! other info that might help us debug this: 3 locks held by syz-executor/4018: #0: [ 36.220068] ( sock_diag_mutex[ 36.220068] ){+.+.+.} , at: [ 36.220068] [] sock_diag_rcv+0x1b/0x40 #1: [ 36.220068] ( sock_diag_table_mutex[ 36.220068] ){+.+.+.} , at: [ 36.220068] [] sock_diag_rcv_msg+0x140/0x3a0 #2: [ 36.220068] ( nlk->cb_mutex[ 36.220068] ){+.+.+.} , at: [ 36.220068] [] netlink_dump+0x50/0xac0 stack backtrace: CPU: 1 PID: 4018 Comm: syz-executor Not tainted 4.9.0-rc3+ #336 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 ffff8800645df688 ffffffff81b46934 ffffffff84eb3e78 ffff88006ad85800 ffffffff82dc8683 ffffffff84eb3e78 ffff8800645df6b8 ffffffff812043ca dffffc0000000000 ffff88006ad85ff8 ffff88006ad85fd0 00000000ffffffff Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [] dump_stack+0xb3/0x10f lib/dump_stack.c:51 [] print_unlock_imbalance_bug+0x17a/0x1a0 kernel/locking/lockdep.c:3388 [< inline >] __lock_release kernel/locking/lockdep.c:3512 [] lock_release+0x8e8/0xc60 kernel/locking/lockdep.c:3765 [< inline >] __raw_read_unlock ./include/linux/rwlock_api_smp.h:225 [] _raw_read_unlock+0x1a/0x30 kernel/locking/spinlock.c:255 [] netlink_diag_dump+0x1a3/0x250 net/netlink/diag.c:182 [] netlink_dump+0x397/0xac0 net/netlink/af_netlink.c:2110 Fixes: ad202074320c ("netlink: Use rhashtable walk interface in diag dump") Signed-off-by: Eric Dumazet Reported-by: Andrey Konovalov Tested-by: Andrey Konovalov Signed-off-by: David S. Miller --- net/netlink/diag.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/net/netlink/diag.c b/net/netlink/diag.c index b2f0e986a6f49..a5546249fb102 100644 --- a/net/netlink/diag.c +++ b/net/netlink/diag.c @@ -178,11 +178,8 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) } cb->args[1] = i; } else { - if (req->sdiag_protocol >= MAX_LINKS) { - read_unlock(&nl_table_lock); - rcu_read_unlock(); + if (req->sdiag_protocol >= MAX_LINKS) return -ENOENT; - } err = __netlink_diag_dump(skb, cb, req->sdiag_protocol, s_num); }