| From: "Steven Rostedt (VMware)" <rostedt@goodmis.org> |
| Date: Tue, 24 Jul 2018 19:13:31 -0400 |
| Subject: tracing: Fix double free of event_trigger_data |
| |
| commit 1863c387259b629e4ebfb255495f67cd06aa229b upstream. |
| |
| 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/20180724191331.738eb819@gandalf.local.home |
| |
| Cc: stable@vger.kerne.org |
| Fixes: 93e31ffbf417 ("tracing: Add 'snapshot' event trigger command") |
| Reported-by: Masami Hiramatsu <mhiramat@kernel.org> |
| Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> |
| Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| kernel/trace/trace_events_trigger.c | 12 ++++++++---- |
| 1 file changed, 8 insertions(+), 4 deletions(-) |
| |
| --- a/kernel/trace/trace_events_trigger.c |
| +++ b/kernel/trace/trace_events_trigger.c |
| @@ -663,6 +663,8 @@ event_trigger_callback(struct event_comm |
| 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, |
| @@ -670,11 +672,13 @@ event_trigger_callback(struct event_comm |
| * 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; |
| |