From 20e6074eb8e096b3a595c093d1cb222f378cd671 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 22 Aug 2011 19:32:42 +0000 Subject: [PATCH] arp: fix rcu lockdep splat in arp_process() Dave Jones reported a lockdep splat triggered by an arp_process() call from parp_redo(). Commit faa9dcf793be (arp: RCU changes) is the origin of the bug, since it assumed arp_process() was called under rcu_read_lock(), which is not true in this particular path. Instead of adding rcu_read_lock() in parp_redo(), I chose to add it in neigh_proxy_process() to take care of IPv6 side too. =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- include/linux/inetdevice.h:209 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 4 locks held by setfiles/2123: #0: (&sb->s_type->i_mutex_key#13){+.+.+.}, at: [] walk_component+0x1ef/0x3e8 #1: (&isec->lock){+.+.+.}, at: [] inode_doinit_with_dentry+0x3f/0x41f #2: (&tbl->proxy_timer){+.-...}, at: [] run_timer_softirq+0x157/0x372 #3: (class){+.-...}, at: [] neigh_proxy_process +0x36/0x103 stack backtrace: Pid: 2123, comm: setfiles Tainted: G W 3.1.0-0.rc2.git7.2.fc16.x86_64 #1 Call Trace: [] lockdep_rcu_dereference+0xa7/0xaf [] __in_dev_get_rcu+0x55/0x5d [] arp_process+0x25/0x4d7 [] parp_redo+0xe/0x10 [] neigh_proxy_process+0x9a/0x103 [] run_timer_softirq+0x218/0x372 [] ? run_timer_softirq+0x157/0x372 [] ? neigh_stat_seq_open+0x41/0x41 [] ? mark_held_locks+0x6d/0x95 [] __do_softirq+0x112/0x25a [] call_softirq+0x1c/0x30 [] do_softirq+0x4b/0xa2 [] irq_exit+0x5d/0xcf [] smp_apic_timer_interrupt+0x7c/0x8a [] apic_timer_interrupt+0x73/0x80 [] ? trace_hardirqs_on_caller+0x121/0x158 [] ? __slab_free+0x30/0x24c [] ? __slab_free+0x2e/0x24c [] ? inode_doinit_with_dentry+0x2e9/0x41f [] ? inode_doinit_with_dentry+0x2e9/0x41f [] ? inode_doinit_with_dentry+0x2e9/0x41f [] kfree+0x108/0x131 [] inode_doinit_with_dentry+0x2e9/0x41f [] selinux_d_instantiate+0x1c/0x1e [] security_d_instantiate+0x21/0x23 [] d_instantiate+0x5c/0x61 [] d_splice_alias+0xbc/0xd2 [] ext4_lookup+0xba/0xeb [] d_alloc_and_lookup+0x45/0x6b [] walk_component+0x215/0x3e8 [] lookup_last+0x3b/0x3d [] path_lookupat+0x82/0x2af [] ? might_fault+0xa5/0xac [] ? might_fault+0x5c/0xac [] ? getname_flags+0x31/0x1ca [] do_path_lookup+0x28/0x97 [] user_path_at+0x59/0x96 [] ? cp_new_stat+0xf7/0x10d [] vfs_fstatat+0x44/0x6e [] vfs_lstat+0x1e/0x20 [] sys_newlstat+0x1a/0x33 [] ? trace_hardirqs_on_caller+0x121/0x158 [] ? trace_hardirqs_on_thunk+0x3a/0x3f [] system_call_fastpath+0x16/0x1b Reported-by: Dave Jones Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/neighbour.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 8fab9b0bb20..1334d7e56f0 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1319,11 +1319,15 @@ static void neigh_proxy_process(unsigned long arg) if (tdif <= 0) { struct net_device *dev = skb->dev; + __skb_unlink(skb, &tbl->proxy_queue); - if (tbl->proxy_redo && netif_running(dev)) + if (tbl->proxy_redo && netif_running(dev)) { + rcu_read_lock(); tbl->proxy_redo(skb); - else + rcu_read_unlock(); + } else { kfree_skb(skb); + } dev_put(dev); } else if (!sched_next || tdif < sched_next)