1. 03 Mar, 2016 4 commits
    • Zheng Liu's avatar
      bcache: unregister reboot notifier if bcache fails to unregister device · 9fac6600
      Zheng Liu authored
      commit 2ecf0cdb upstream.
      
      In bcache_init() function it forgot to unregister reboot notifier if
      bcache fails to unregister a block device.  This commit fixes this.
      Signed-off-by: default avatarZheng Liu <wenqing.lz@taobao.com>
      Tested-by: default avatarJoshua Schmid <jschmid@suse.com>
      Tested-by: default avatarEric Wheeler <bcache@linux.ewheeler.net>
      Cc: Kent Overstreet <kmo@daterainc.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      9fac6600
    • Andrey Vagin's avatar
      netfilter: nf_conntrack: fix RCU race in nf_conntrack_find_get · f79d019c
      Andrey Vagin authored
      commit c6825c09 upstream.
      
      Lets look at destroy_conntrack:
      
      hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
      ...
      nf_conntrack_free(ct)
      	kmem_cache_free(net->ct.nf_conntrack_cachep, ct);
      
      net->ct.nf_conntrack_cachep is created with SLAB_DESTROY_BY_RCU.
      
      The hash is protected by rcu, so readers look up conntracks without
      locks.
      A conntrack is removed from the hash, but in this moment a few readers
      still can use the conntrack. Then this conntrack is released and another
      thread creates conntrack with the same address and the equal tuple.
      After this a reader starts to validate the conntrack:
      * It's not dying, because a new conntrack was created
      * nf_ct_tuple_equal() returns true.
      
      But this conntrack is not initialized yet, so it can not be used by two
      threads concurrently. In this case BUG_ON may be triggered from
      nf_nat_setup_info().
      
      Florian Westphal suggested to check the confirm bit too. I think it's
      right.
      
      task 1			task 2			task 3
      			nf_conntrack_find_get
      			 ____nf_conntrack_find
      destroy_conntrack
       hlist_nulls_del_rcu
       nf_conntrack_free
       kmem_cache_free
      						__nf_conntrack_alloc
      						 kmem_cache_alloc
      						 memset(&ct->tuplehash[IP_CT_DIR_MAX],
      			 if (nf_ct_is_dying(ct))
      			 if (!nf_ct_tuple_equal()
      
      I'm not sure, that I have ever seen this race condition in a real life.
      Currently we are investigating a bug, which is reproduced on a few nodes.
      In our case one conntrack is initialized from a few tasks concurrently,
      we don't have any other explanation for this.
      
      <2>[46267.083061] kernel BUG at net/ipv4/netfilter/nf_nat_core.c:322!
      ...
      <4>[46267.083951] RIP: 0010:[<ffffffffa01e00a4>]  [<ffffffffa01e00a4>] nf_nat_setup_info+0x564/0x590 [nf_nat]
      ...
      <4>[46267.085549] Call Trace:
      <4>[46267.085622]  [<ffffffffa023421b>] alloc_null_binding+0x5b/0xa0 [iptable_nat]
      <4>[46267.085697]  [<ffffffffa02342bc>] nf_nat_rule_find+0x5c/0x80 [iptable_nat]
      <4>[46267.085770]  [<ffffffffa0234521>] nf_nat_fn+0x111/0x260 [iptable_nat]
      <4>[46267.085843]  [<ffffffffa0234798>] nf_nat_out+0x48/0xd0 [iptable_nat]
      <4>[46267.085919]  [<ffffffff814841b9>] nf_iterate+0x69/0xb0
      <4>[46267.085991]  [<ffffffff81494e70>] ? ip_finish_output+0x0/0x2f0
      <4>[46267.086063]  [<ffffffff81484374>] nf_hook_slow+0x74/0x110
      <4>[46267.086133]  [<ffffffff81494e70>] ? ip_finish_output+0x0/0x2f0
      <4>[46267.086207]  [<ffffffff814b5890>] ? dst_output+0x0/0x20
      <4>[46267.086277]  [<ffffffff81495204>] ip_output+0xa4/0xc0
      <4>[46267.086346]  [<ffffffff814b65a4>] raw_sendmsg+0x8b4/0x910
      <4>[46267.086419]  [<ffffffff814c10fa>] inet_sendmsg+0x4a/0xb0
      <4>[46267.086491]  [<ffffffff814459aa>] ? sock_update_classid+0x3a/0x50
      <4>[46267.086562]  [<ffffffff81444d67>] sock_sendmsg+0x117/0x140
      <4>[46267.086638]  [<ffffffff8151997b>] ? _spin_unlock_bh+0x1b/0x20
      <4>[46267.086712]  [<ffffffff8109d370>] ? autoremove_wake_function+0x0/0x40
      <4>[46267.086785]  [<ffffffff81495e80>] ? do_ip_setsockopt+0x90/0xd80
      <4>[46267.086858]  [<ffffffff8100be0e>] ? call_function_interrupt+0xe/0x20
      <4>[46267.086936]  [<ffffffff8118cb10>] ? ub_slab_ptr+0x20/0x90
      <4>[46267.087006]  [<ffffffff8118cb10>] ? ub_slab_ptr+0x20/0x90
      <4>[46267.087081]  [<ffffffff8118f2e8>] ? kmem_cache_alloc+0xd8/0x1e0
      <4>[46267.087151]  [<ffffffff81445599>] sys_sendto+0x139/0x190
      <4>[46267.087229]  [<ffffffff81448c0d>] ? sock_setsockopt+0x16d/0x6f0
      <4>[46267.087303]  [<ffffffff810efa47>] ? audit_syscall_entry+0x1d7/0x200
      <4>[46267.087378]  [<ffffffff810ef795>] ? __audit_syscall_exit+0x265/0x290
      <4>[46267.087454]  [<ffffffff81474885>] ? compat_sys_setsockopt+0x75/0x210
      <4>[46267.087531]  [<ffffffff81474b5f>] compat_sys_socketcall+0x13f/0x210
      <4>[46267.087607]  [<ffffffff8104dea3>] ia32_sysret+0x0/0x5
      <4>[46267.087676] Code: 91 20 e2 01 75 29 48 89 de 4c 89 f7 e8 56 fa ff ff 85 c0 0f 84 68 fc ff ff 0f b6 4d c6 41 8b 45 00 e9 4d fb ff ff e8 7c 19 e9 e0 <0f> 0b eb fe f6 05 17 91 20 e2 80 74 ce 80 3d 5f 2e 00 00 00 74
      <1>[46267.088023] RIP  [<ffffffffa01e00a4>] nf_nat_setup_info+0x564/0x590
      
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: Florian Westphal <fw@strlen.de>
      Cc: Pablo Neira Ayuso <pablo@netfilter.org>
      Cc: Patrick McHardy <kaber@trash.net>
      Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Cyrill Gorcunov <gorcunov@openvz.org>
      Signed-off-by: default avatarAndrey Vagin <avagin@openvz.org>
      Acked-by: default avatarEric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      f79d019c
    • Egbert Eich's avatar
      drm/ast: Initialized data needed to map fbdev memory · 9f5bc010
      Egbert Eich authored
      commit 28fb4cb7 upstream.
      
      Due to a missing initialization there was no way to map fbdev memory.
      Thus for example using the Xserver with the fbdev driver failed.
      This fix adds initialization for fix.smem_start and fix.smem_len
      in the fb_info structure, which fixes this problem.
      Requested-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
      Signed-off-by: default avatarEgbert Eich <eich@suse.de>
      [pulled from SuSE tree by me - airlied]
      Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      9f5bc010
    • Steven Rostedt (Red Hat)'s avatar
      tracepoints: Do not trace when cpu is offline · c3e07084
      Steven Rostedt (Red Hat) authored
      commit f3775549 upstream.
      
      The tracepoint infrastructure uses RCU sched protection to enable and
      disable tracepoints safely. There are some instances where tracepoints are
      used in infrastructure code (like kfree()) that get called after a CPU is
      going offline, and perhaps when it is coming back online but hasn't been
      registered yet.
      
      This can probuce the following warning:
      
       [ INFO: suspicious RCU usage. ]
       4.4.0-00006-g0fe53e8-dirty #34 Tainted: G S
       -------------------------------
       include/trace/events/kmem.h:141 suspicious rcu_dereference_check() usage!
      
       other info that might help us debug this:
      
       RCU used illegally from offline CPU!  rcu_scheduler_active = 1, debug_locks = 1
       no locks held by swapper/8/0.
      
       stack backtrace:
        CPU: 8 PID: 0 Comm: swapper/8 Tainted: G S              4.4.0-00006-g0fe53e8-dirty #34
        Call Trace:
        [c0000005b76c78d0] [c0000000008b9540] .dump_stack+0x98/0xd4 (unreliable)
        [c0000005b76c7950] [c00000000010c898] .lockdep_rcu_suspicious+0x108/0x170
        [c0000005b76c79e0] [c00000000029adc0] .kfree+0x390/0x440
        [c0000005b76c7a80] [c000000000055f74] .destroy_context+0x44/0x100
        [c0000005b76c7b00] [c0000000000934a0] .__mmdrop+0x60/0x150
        [c0000005b76c7b90] [c0000000000e3ff0] .idle_task_exit+0x130/0x140
        [c0000005b76c7c20] [c000000000075804] .pseries_mach_cpu_die+0x64/0x310
        [c0000005b76c7cd0] [c000000000043e7c] .cpu_die+0x3c/0x60
        [c0000005b76c7d40] [c0000000000188d8] .arch_cpu_idle_dead+0x28/0x40
        [c0000005b76c7db0] [c000000000101e6c] .cpu_startup_entry+0x50c/0x560
        [c0000005b76c7ed0] [c000000000043bd8] .start_secondary+0x328/0x360
        [c0000005b76c7f90] [c000000000008a6c] start_secondary_prolog+0x10/0x14
      
      This warning is not a false positive either. RCU is not protecting code that
      is being executed while the CPU is offline.
      
      Instead of playing "whack-a-mole(TM)" and adding conditional statements to
      the tracepoints we find that are used in this instance, simply add a
      cpu_online() test to the tracepoint code where the tracepoint will be
      ignored if the CPU is offline.
      
      Use of raw_smp_processor_id() is fine, as there should never be a case where
      the tracepoint code goes from running on a CPU that is online and suddenly
      gets migrated to a CPU that is offline.
      
      Link: http://lkml.kernel.org/r/1455387773-4245-1-git-send-email-kda@linux-powerpc.orgReported-by: default avatarDenis Kirjanov <kda@linux-powerpc.org>
      Fixes: 97e1c18e ("tracing: Kernel Tracepoints")
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      c3e07084
  2. 25 Feb, 2016 36 commits