On Mon, Mar 24, 2014 at 12:06:21PM +0000, Dmitry Malkin wrote:
Hello guys,
I've been playing with reloading intel gfx driver (i915) in a cycle, for a while, and at some point I've found a non-deterministic kernel crash with a highly-variable iteration dependency -- 2 to 200 driver reload iterations.
The apparent race is over the shared internal string buffer in drm_get_connector_name(). It is mostly harmless, due to its results being mostly used for log output, but in at least one case -- drm_sysfs_connector_add() -- this leads to a more critical error.
Race scenario:
- drm_sysfs_connector_add()
- drm_get_connector_name()
vs.
- anything that generates log messages involving DRM connectors
- drm_get_connector_name()
(and many other from drm_crtc.c) shares with caller const char* to internal static char buffer. If something call it from other thread, while main thread strore and use returned pointer it may overwrite connector name.
Here are we go: registering HDMI connecter (drm_sysfs_connector_add store and use pointer from drm_get_connector_name) and the same time got VGA connector name down through the stack. (the second thread is upowerd who watch continuously sysfs)
Yeah, in my recent kerneldoc series I've noticed this too and added FIXME comments. There's a lot more than just those you've pointed out. The problem is that fixing these will be an awful lot of work since you need to add proper cleanup code (calling kfree()) to all the required places.
So a full subsystem wide code audit for every single use-site of these. -Daniel
Mar 24 14:23:04 haswell01 kernel: [ 417.570043] ------------[ cut here ]------------ Mar 24 14:23:04 haswell01 kernel: [ 417.570045] WARNING: CPU: 0 PID: 12700 at /build/buildd/linux-3.13.0/lib/kobject.c:223 kobject_add_internal+0x224/0x330() Mar 24 14:23:04 haswell01 kernel: [ 417.570046] kobject_add_internal failed for card0-VGA-1 with -EEXIST, don't try to register things with the same name in the same directory. Mar 24 14:23:04 haswell01 kernel: [ 417.570047] Modules linked in: i915(+) video drm_kms_helper drm i2c_algo_bit snd_hda_codec_realtek snd_hda_codec_hdmi bnep rfcomm bluetooth x86_pkg_temp_thermal intel_p owerclamp coretemp kvm_intel snd_hda_codec kvm snd_hwdep snd_pcm hid_generic snd_page_alloc crct10dif_pclmul snd_seq_midi crc32_pclmul ghash_clmulni_intel snd_seq_midi_event usbhid snd_rawmidi hid aesni_in tel aes_x86_64 lrw gf128mul ppdev glue_helper ablk_helper cryptd snd_seq snd_seq_device snd_timer snd mei_me psmouse lpc_ich soundcore mei mac_hid parport_pc serio_raw nls_iso8859_1 lp parport e1000e ahci ptp libahci pps_core [last unloaded: video] Mar 24 14:23:04 haswell01 kernel: [ 417.570068] CPU: 0 PID: 12700 Comm: modprobe Tainted: G W 3.13.0-19-generic #39-Ubuntu Mar 24 14:23:04 haswell01 kernel: [ 417.570069] Hardware name: /DQ87PG, BIOS PGQ8710H.86A.0144.2014.0113.1604 01/13/2014 Mar 24 14:23:04 haswell01 kernel: [ 417.570069] 0000000000000009 ffff8804051295f8 ffffffff81711075 ffff880405129640 Mar 24 14:23:04 haswell01 kernel: [ 417.570071] ffff880405129630 ffffffff810662cd ffff88040776a410 00000000ffffffef Mar 24 14:23:04 haswell01 kernel: [ 417.570074] 0000000000000000 ffff8804048dcc10 ffff880407769000 ffff880405129690 Mar 24 14:23:04 haswell01 kernel: [ 417.570076] Call Trace: Mar 24 14:23:04 haswell01 kernel: [ 417.570078] [<ffffffff81711075>] dump_stack+0x45/0x56 Mar 24 14:23:04 haswell01 kernel: [ 417.570080] [<ffffffff810662cd>] warn_slowpath_common+0x7d/0xa0 Mar 24 14:23:04 haswell01 kernel: [ 417.570081] [<ffffffff8106633c>] warn_slowpath_fmt+0x4c/0x50 Mar 24 14:23:04 haswell01 kernel: [ 417.570082] [<ffffffff81230083>] ? sysfs_create_dir_ns+0x73/0xc0 Mar 24 14:23:04 haswell01 kernel: [ 417.570084] [<ffffffff8135b9a4>] kobject_add_internal+0x224/0x330 Mar 24 14:23:04 haswell01 kernel: [ 417.570086] [<ffffffff8135bed5>] kobject_add+0x65/0xb0 Mar 24 14:23:04 haswell01 kernel: [ 417.570088] [<ffffffff814874f5>] device_add+0x125/0x640 Mar 24 14:23:04 haswell01 kernel: [ 417.570090] [<ffffffff81487c20>] device_create_groups_vargs+0xe0/0x110 Mar 24 14:23:04 haswell01 kernel: [ 417.570092] [<ffffffff81487cb1>] device_create+0x41/0x50 Mar 24 14:23:04 haswell01 kernel: [ 417.570097] [<ffffffffa0137fc9>] drm_sysfs_connector_add+0x69/0x230 [drm] Mar 24 14:23:04 haswell01 kernel: [ 417.570110] [<ffffffffa0549ca1>] intel_hdmi_init_connector+0x111/0x260 [i915] Mar 24 14:23:04 haswell01 kernel: [ 417.570119] [<ffffffffa0541670>] intel_ddi_init+0x270/0x2a0 [i915] Mar 24 14:23:04 haswell01 kernel: [ 417.570130] [<ffffffffa0533176>] intel_setup_outputs+0x4c6/0x750 [i915] Mar 24 14:23:04 haswell01 kernel: [ 417.570139] [<ffffffffa05370f7>] intel_modeset_init+0x607/0x8f0 [i915] Mar 24 14:23:04 haswell01 kernel: [ 417.570147] [<ffffffffa04f90a4>] i915_driver_load+0xbb4/0xe70 [i915] Mar 24 14:23:04 haswell01 kernel: [ 417.570153] [<ffffffffa0134cd2>] drm_dev_register+0xa2/0x1e0 [drm] Mar 24 14:23:04 haswell01 kernel: [ 417.570158] [<ffffffffa0136bc2>] drm_get_pci_dev+0x92/0x140 [drm] Mar 24 14:23:04 haswell01 kernel: [ 417.570166] [<ffffffffa04f567c>] i915_pci_probe+0x3c/0x90 [i915] Mar 24 14:23:04 haswell01 kernel: [ 417.570168] [<ffffffff8139e0e5>] local_pci_probe+0x45/0xa0 Mar 24 14:23:04 haswell01 kernel: [ 417.570170] [<ffffffff8139f385>] ? pci_match_device+0xc5/0xd0 Mar 24 14:23:04 haswell01 kernel: [ 417.570172] [<ffffffff8139f4a9>] pci_device_probe+0xd9/0x130 Mar 24 14:23:04 haswell01 kernel: [ 417.570174] [<ffffffff8148a7c5>] driver_probe_device+0x125/0x3b0 Mar 24 14:23:04 haswell01 kernel: [ 417.570176] [<ffffffff8148ab23>] __driver_attach+0x93/0xa0 Mar 24 14:23:04 haswell01 kernel: [ 417.570178] [<ffffffff8148aa90>] ? __device_attach+0x40/0x40 Mar 24 14:23:04 haswell01 kernel: [ 417.570179] [<ffffffff81488733>] bus_for_each_dev+0x63/0xa0 Mar 24 14:23:04 haswell01 kernel: [ 417.570181] [<ffffffff8148a17e>] driver_attach+0x1e/0x20 Mar 24 14:23:04 haswell01 kernel: [ 417.570183] [<ffffffff81489d60>] bus_add_driver+0x180/0x250 Mar 24 14:23:04 haswell01 kernel: [ 417.570185] [<ffffffffa01be000>] ? 0xffffffffa01bdfff Mar 24 14:23:04 haswell01 kernel: [ 417.570187] [<ffffffff8148b1a4>] driver_register+0x64/0xf0 Mar 24 14:23:04 haswell01 kernel: [ 417.570189] [<ffffffffa01be000>] ? 0xffffffffa01bdfff Mar 24 14:23:04 haswell01 kernel: [ 417.570191] [<ffffffff8139da7c>] __pci_register_driver+0x4c/0x50 Mar 24 14:23:04 haswell01 kernel: [ 417.570196] [<ffffffffa0136d8a>] drm_pci_init+0x11a/0x130 [drm] Mar 24 14:23:04 haswell01 kernel: [ 417.570198] [<ffffffffa01be000>] ? 0xffffffffa01bdfff Mar 24 14:23:04 haswell01 kernel: [ 417.570205] [<ffffffffa01be066>] i915_init+0x66/0x68 [i915] Mar 24 14:23:04 haswell01 kernel: [ 417.570207] [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0 Mar 24 14:23:04 haswell01 kernel: [ 417.570208] [<ffffffff81058ae3>] ? set_memory_nx+0x43/0x50 Mar 24 14:23:04 haswell01 kernel: [ 417.570211] [<ffffffff810e091d>] load_module+0x12dd/0x1b40 Mar 24 14:23:04 haswell01 kernel: [ 417.570213] [<ffffffff810dc3a0>] ? store_uevent+0x40/0x40 Mar 24 14:23:04 haswell01 kernel: [ 417.570215] [<ffffffff810e12f6>] SyS_finit_module+0x86/0xb0 Mar 24 14:23:04 haswell01 kernel: [ 417.570217] [<ffffffff81721c7f>] tracesys+0xe1/0xe6 Mar 24 14:23:04 haswell01 kernel: [ 417.570219] ---[ end trace 8cd466c13137554f ]---
How to reproduce: load/reload i915 driver many times (in my case it happens after 2-200 attempts) and you will got a sysfs dup warning and then while unloading driver it will crash (because of malformed connectors list):
Mar 24 14:23:16 haswell01 kernel: [ 429.326174] BUG: unable to handle kernel NULL pointer dereference at 000000000000002f Mar 24 14:23:16 haswell01 kernel: [ 429.326177] IP: [<ffffffff8122de46>] sysfs_remove_file_ns+0x6/0x20 Mar 24 14:23:16 haswell01 kernel: [ 429.326184] PGD 3f588d067 PUD 406361067 PMD 0 Mar 24 14:23:16 haswell01 kernel: [ 429.326187] Oops: 0000 [#1] SMP Mar 24 14:23:16 haswell01 kernel: [ 429.326189] Modules linked in: i915 video drm_kms_helper drm i2c_algo_bit snd_hda_codec_realtek snd_hda_codec_hdmi bnep rfcomm bluetooth x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel snd_hda_codec kvm snd_hwdep snd_pcm hid_generic snd_page_alloc crct10dif_pclmul snd_seq_midi crc32_pclmul ghash_clmulni_intel snd_seq_midi_event usbhid snd_rawmidi hid aesni_intel aes_x86_64 lrw gf128mul ppdev glue_helper ablk_helper cryptd snd_seq snd_seq_device snd_timer snd mei_me psmouse lpc_ich soundcore mei mac_hid parport_pc serio_raw nls_iso8859_1 lp parport e1000e ahci ptp libahci pps_core [last unloaded: video] Mar 24 14:23:16 haswell01 kernel: [ 429.326219] CPU: 0 PID: 13302 Comm: dd Tainted: G W 3.13.0-19-generic #39-Ubuntu Mar 24 14:23:16 haswell01 kernel: [ 429.326221] Hardware name: /DQ87PG, BIOS PGQ8710H.86A.0144.2014.0113.1604 01/13/2014 Mar 24 14:23:16 haswell01 kernel: [ 429.326222] task: ffff8803f5aaafe0 ti: ffff880404d20000 task.ti: ffff880404d20000 Mar 24 14:23:16 haswell01 kernel: [ 429.326224] RIP: 0010:[<ffffffff8122de46>] [<ffffffff8122de46>] sysfs_remove_file_ns+0x6/0x20 Mar 24 14:23:16 haswell01 kernel: [ 429.326227] RSP: 0018:ffff880404d21d20 EFLAGS: 00010246 Mar 24 14:23:16 haswell01 kernel: [ 429.326228] RAX: 0000000000000000 RBX: ffffffffa0160160 RCX: ffffffffa0159356 Mar 24 14:23:16 haswell01 kernel: [ 429.326230] RDX: 0000000000000000 RSI: ffffffffa0160140 RDI: ffffffffffffffff Mar 24 14:23:16 haswell01 kernel: [ 429.326231] RBP: ffff880404d21d30 R08: ffffffffa0161120 R09: 000000000000fffe Mar 24 14:23:16 haswell01 kernel: [ 429.326232] R10: 0000000000000000 R11: ffffea0010199f80 R12: ffff880407769000 Mar 24 14:23:16 haswell01 kernel: [ 429.326234] R13: ffff880035d46af8 R14: ffff880035d46820 R15: ffffffffffffffed Mar 24 14:23:16 haswell01 kernel: [ 429.326236] FS: 00007f472f4ec740(0000) GS:ffff88041ea00000(0000) knlGS:0000000000000000 Mar 24 14:23:16 haswell01 kernel: [ 429.326238] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Mar 24 14:23:16 haswell01 kernel: [ 429.326239] CR2: 000000000000002f CR3: 00000004050d3000 CR4: 00000000001407f0 Mar 24 14:23:16 haswell01 kernel: [ 429.326241] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Mar 24 14:23:16 haswell01 kernel: [ 429.326242] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Mar 24 14:23:16 haswell01 kernel: [ 429.326243] Stack: Mar 24 14:23:16 haswell01 kernel: [ 429.326244] ffff880404d21d30 ffffffff81485a59 ffff880404d21d50 ffffffffa0137eb7 Mar 24 14:23:16 haswell01 kernel: [ 429.326247] ffff880407769000 ffff880035d46800 ffff880404d21d80 ffffffffa05381d0 Mar 24 14:23:16 haswell01 kernel: [ 429.326250] ffff8803f24e4000 ffff880035d46800 ffff8804081b9000 000000000000000c Mar 24 14:23:16 haswell01 kernel: [ 429.326253] Call Trace: Mar 24 14:23:16 haswell01 kernel: [ 429.326257] [<ffffffff81485a59>] ? device_remove_file+0x19/0x20 Mar 24 14:23:16 haswell01 kernel: [ 429.326267] [<ffffffffa0137eb7>] drm_sysfs_connector_remove+0x57/0x90 [drm] Mar 24 14:23:16 haswell01 kernel: [ 429.326282] [<ffffffffa05381d0>] intel_modeset_cleanup+0xd0/0x100 [i915] Mar 24 14:23:16 haswell01 kernel: [ 429.326288] [<ffffffffa04f95f0>] i915_driver_unload+0x290/0x340 [i915] Mar 24 14:23:16 haswell01 kernel: [ 429.326294] [<ffffffffa01346fc>] drm_dev_unregister+0x2c/0xe0 [drm] Mar 24 14:23:16 haswell01 kernel: [ 429.326299] [<ffffffffa01347eb>] drm_put_dev+0x3b/0x70 [drm] Mar 24 14:23:16 haswell01 kernel: [ 429.326304] [<ffffffffa04f558d>] i915_pci_remove+0x1d/0x20 [i915] Mar 24 14:23:16 haswell01 kernel: [ 429.326307] [<ffffffff8139efbb>] pci_device_remove+0x3b/0xb0 Mar 24 14:23:16 haswell01 kernel: [ 429.326310] [<ffffffff8148a24f>] __device_release_driver+0x7f/0xf0 Mar 24 14:23:16 haswell01 kernel: [ 429.326313] [<ffffffff8148a2e3>] device_release_driver+0x23/0x30 Mar 24 14:23:16 haswell01 kernel: [ 429.326315] [<ffffffff8148905d>] unbind_store+0xbd/0xe0 Mar 24 14:23:16 haswell01 kernel: [ 429.326317] [<ffffffff81488484>] drv_attr_store+0x24/0x40 Mar 24 14:23:16 haswell01 kernel: [ 429.326320] [<ffffffff8122e698>] sysfs_write_file+0x128/0x1c0 Mar 24 14:23:16 haswell01 kernel: [ 429.326323] [<ffffffff811b88c4>] vfs_write+0xb4/0x1f0 Mar 24 14:23:16 haswell01 kernel: [ 429.326325] [<ffffffff811b92f9>] SyS_write+0x49/0xa0 Mar 24 14:23:16 haswell01 kernel: [ 429.326328] [<ffffffff81721c7f>] tracesys+0xe1/0xe6 Mar 24 14:23:16 haswell01 kernel: [ 429.326329] Code: 58 c7 81 e8 7d 98 4e 00 48 83 c4 50 89 d8 5b 41 5c 41 5d 5d c3 bb fe ff ff ff eb e0 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 <48> 8b 7f 30 48 8b 36 48 89 e5 e8 bb 22 00 00 5d c3 66 0f 1f 84 Mar 24 14:23:16 haswell01 kernel: [ 429.326351] RIP [<ffffffff8122de46>] sysfs_remove_file_ns+0x6/0x20 Mar 24 14:23:16 haswell01 kernel: [ 429.326353] RSP <ffff880404d21d20> Mar 24 14:23:16 haswell01 kernel: [ 429.326355] CR2: 000000000000002f Mar 24 14:23:16 haswell01 kernel: [ 429.326356] ---[ end trace 8cd466c131375550 ]---
dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel