From 30842f2989aacfaba3ccb39829b3417be9313dbe Mon Sep 17 00:00:00 2001 From: Vitaly Mayatskikh Date: Mon, 23 Mar 2009 15:22:33 -0700 Subject: [PATCH] udp: Wrong locking code in udp seq_file infrastructure Reading zero bytes from /proc/net/udp or other similar files which use the same seq_file udp infrastructure panics kernel in that way: ===================================== [ BUG: bad unlock balance detected! ] ------------------------------------- read/1985 is trying to release lock (&table->hash[i].lock) at: [] udp_seq_stop+0x27/0x29 but there are no more locks to release! other info that might help us debug this: 1 lock held by read/1985: #0: (&p->lock){--..}, at: [] seq_read+0x38/0x348 stack backtrace: Pid: 1985, comm: read Not tainted 2.6.29-rc8 #9 Call Trace: [] ? udp_seq_stop+0x27/0x29 [] print_unlock_inbalance_bug+0xd6/0xe1 [] lock_release_non_nested+0x9e/0x1c6 [] ? seq_read+0xb2/0x348 [] ? mark_held_locks+0x68/0x86 [] ? udp_seq_stop+0x27/0x29 [] lock_release+0x15d/0x189 [] _spin_unlock_bh+0x1e/0x34 [] udp_seq_stop+0x27/0x29 [] seq_read+0x2bb/0x348 [] ? seq_read+0x0/0x348 [] proc_reg_read+0x90/0xaf [] vfs_read+0xa6/0x103 [] ? trace_hardirqs_on_caller+0x12f/0x153 [] sys_read+0x45/0x69 [] system_call_fastpath+0x16/0x1b BUG: scheduling while atomic: read/1985/0xffffff00 INFO: lockdep is turned off. Modules linked in: cpufreq_ondemand acpi_cpufreq freq_table dm_multipath kvm ppdev snd_hda_codec_analog snd_hda_intel snd_hda_codec snd_hwdep snd_seq_dummy snd_seq_oss snd_seq_midi_event arc4 snd_s eq ecb thinkpad_acpi snd_seq_device iwl3945 hwmon sdhci_pci snd_pcm_oss sdhci rfkill mmc_core snd_mixer_oss i2c_i801 mac80211 yenta_socket ricoh_mmc i2c_core iTCO_wdt snd_pcm iTCO_vendor_support rs rc_nonstatic snd_timer snd lib80211 cfg80211 soundcore snd_page_alloc video parport_pc output parport e1000e [last unloaded: scsi_wait_scan] Pid: 1985, comm: read Not tainted 2.6.29-rc8 #9 Call Trace: [] ? __debug_show_held_locks+0x1b/0x24 [] __schedule_bug+0x7e/0x83 [] schedule+0xce/0x838 [] ? fsnotify_access+0x5f/0x67 [] ? sysret_careful+0xb/0x37 [] ? trace_hardirqs_on_caller+0x1f/0x153 [] ? trace_hardirqs_on_thunk+0x3a/0x3f [] sysret_careful+0x31/0x37 read[1985]: segfault at 7fffc479bfe8 ip 0000003e7420a180 sp 00007fffc479bfa0 error 6 Kernel panic - not syncing: Aiee, killing interrupt handler! udp_seq_stop() tries to unlock not yet locked spinlock. The lock was lost during splitting global udp_hash_lock to subsequent spinlocks. Signed-off by: Vitaly Mayatskikh Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/udp.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index c47c989cb1fb..c8bee189a193 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1614,7 +1614,8 @@ static struct sock *udp_get_next(struct seq_file *seq, struct sock *sk) } while (sk && (!net_eq(sock_net(sk), net) || sk->sk_family != state->family)); if (!sk) { - spin_unlock_bh(&state->udp_table->hash[state->bucket].lock); + if (state->bucket < UDP_HTABLE_SIZE) + spin_unlock_bh(&state->udp_table->hash[state->bucket].lock); return udp_get_first(seq, state->bucket + 1); } return sk; @@ -1632,6 +1633,9 @@ static struct sock *udp_get_idx(struct seq_file *seq, loff_t pos) static void *udp_seq_start(struct seq_file *seq, loff_t *pos) { + struct udp_iter_state *state = seq->private; + state->bucket = UDP_HTABLE_SIZE; + return *pos ? udp_get_idx(seq, *pos-1) : SEQ_START_TOKEN; } -- 2.39.2