On Thu, 26 Jul 2018 00:43:49 +0900 Masami Hiramatsu <mhira...@kernel.org> wrote:
> 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> > Hmm, looks to me that event_enable_trigger_func() suffers the same issue. Perhaps we should add this patch too: -- Steve diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index d18ec0e58be2..2681d917f896 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -1457,6 +1457,10 @@ int event_enable_trigger_func(struct event_command *cmd_ops, ret = trace_event_enable_disable(event_enable_file, 1, 1); if (ret < 0) goto out_put; + + /* 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, @@ -1464,12 +1468,13 @@ int event_enable_trigger_func(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_disable; - } else if (ret < 0) - goto out_disable; - /* Just return zero, not the number of enabled functions */ - 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;
