On Wed, 25 Jul 2018 08:57:40 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> From: "Steven Rostedt (VMware)" <rost...@goodmis.org> > > Running the following: > > # cd /sys/kernel/debug/tracing > # echo 500000 > buffer_size_kb > [ Or some other number that takes up most of memory ] > # echo snapshot > events/sched/sched_switch/trigger > > Triggers the following bug: > > ------------[ cut here ]------------ > kernel BUG at mm/slub.c:296! > invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC PTI > CPU: 6 PID: 6878 Comm: bash Not tainted 4.18.0-rc6-test+ #1066 > Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 > 07/14/2016 > RIP: 0010:kfree+0x16c/0x180 > Code: 05 41 0f b6 72 51 5b 5d 41 5c 4c 89 d7 e9 ac b3 f8 ff 48 89 d9 48 89 > da 41 b8 01 00 00 00 5b 5d 41 5c 4c 89 d6 e9 f4 f3 ff ff <0f> 0b 0f 0b 48 8b > 3d d9 d8 f9 00 e9 c1 fe ff ff 0f 1f 40 00 0f 1f > RSP: 0018:ffffb654436d3d88 EFLAGS: 00010246 > RAX: ffff91a9d50f3d80 RBX: ffff91a9d50f3d80 RCX: ffff91a9d50f3d80 > RDX: 00000000000006a4 RSI: ffff91a9de5a60e0 RDI: ffff91a9d9803500 > RBP: ffffffff8d267c80 R08: 00000000000260e0 R09: ffffffff8c1a56be > R10: fffff0d404543cc0 R11: 0000000000000389 R12: ffffffff8c1a56be > R13: ffff91a9d9930e18 R14: ffff91a98c0c2890 R15: ffffffff8d267d00 > FS: 00007f363ea64700(0000) GS:ffff91a9de580000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000055c1cacc8e10 CR3: 00000000d9b46003 CR4: 00000000001606e0 > Call Trace: > event_trigger_callback+0xee/0x1d0 > event_trigger_write+0xfc/0x1a0 > __vfs_write+0x33/0x190 > ? handle_mm_fault+0x115/0x230 > ? _cond_resched+0x16/0x40 > vfs_write+0xb0/0x190 > ksys_write+0x52/0xc0 > do_syscall_64+0x5a/0x160 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x7f363e16ab50 > Code: 73 01 c3 48 8b 0d 38 83 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f > 44 00 00 83 3d 79 db 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff > 73 31 c3 48 83 ec 08 e8 1e e3 01 00 48 89 04 24 > RSP: 002b:00007fff9a4c6378 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f363e16ab50 > RDX: 0000000000000009 RSI: 000055c1cacc8e10 RDI: 0000000000000001 > RBP: 000055c1cacc8e10 R08: 00007f363e435740 R09: 00007f363ea64700 > R10: 0000000000000073 R11: 0000000000000246 R12: 0000000000000009 > R13: 0000000000000001 R14: 00007f363e4345e0 R15: 00007f363e4303c0 > Modules linked in: ip6table_filter ip6_tables snd_hda_codec_hdmi > snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel snd_hda_codec > snd_hwdep snd_hda_core snd_seq snd_seq_device i915 snd_pcm snd_timer i2c_i801 > snd soundcore i2c_algo_bit drm_kms_helper > 86_pkg_temp_thermal video kvm_intel kvm irqbypass wmi e1000e > ---[ end trace d301afa879ddfa25 ]--- > > The cause is because the register_snapshot_trigger() call failed to > allocate the snapshot buffer, and then called unregister_trigger() > which freed the data that was passed to it. Then on return to the > function that called register_snapshot_trigger(), as it sees it > failed to register, it frees the trigger_data again and causes > a double free. > > By calling event_trigger_init() on the trigger_data (which only ups > the reference counter for it), and then event_trigger_free() afterward, > the trigger_data would not get freed by the registering trigger function > as it would only up and lower the ref count for it. If the register > trigger function fails, then the event_trigger_free() called after it > will free the trigger data normally. > > Link: http://lkml.kernel.org/r/20180724191331.738eb...@gandalf.local.home > Looks good to me. Reviewed-by: Masami Hiramatsu <mhira...@kernel.org> Thanks! > Cc: sta...@vger.kerne.org > Fixes: 93e31ffbf417 ("tracing: Add 'snapshot' event trigger command") > Reported-by: Masami Hiramatsu <mhira...@kernel.org> > Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> > --- > kernel/trace/trace_events_trigger.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/trace_events_trigger.c > b/kernel/trace/trace_events_trigger.c > index d18249683682..d18ec0e58be2 100644 > --- a/kernel/trace/trace_events_trigger.c > +++ b/kernel/trace/trace_events_trigger.c > @@ -679,6 +679,8 @@ event_trigger_callback(struct event_command *cmd_ops, > goto out_free; > > out_reg: > + /* Up the trigger_data count to make sure reg doesn't free it on > failure */ > + event_trigger_init(trigger_ops, trigger_data); > ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file); > /* > * The above returns on success the # of functions enabled, > @@ -686,11 +688,13 @@ event_trigger_callback(struct event_command *cmd_ops, > * Consider no functions a failure too. > */ > if (!ret) { > + cmd_ops->unreg(glob, trigger_ops, trigger_data, file); > ret = -ENOENT; > - goto out_free; > - } else if (ret < 0) > - goto out_free; > - ret = 0; > + } else if (ret > 0) > + ret = 0; > + > + /* Down the counter of trigger_data or free it if not used anymore */ > + event_trigger_free(trigger_ops, trigger_data); > out: > return ret; > > -- > 2.13.6 > -- Masami Hiramatsu <mhira...@kernel.org>
