linux

Go to file

Lyude Paul 9765635b30 Revert "drm/dp_mst: Skip validating ports during destruction, just ref" This reverts commit: `c54c7374ff` ("drm/dp_mst: Skip validating ports during destruction, just ref") ugh. In drm_dp_destroy_connector_work(), we have a pretty good chance of freeing the actual struct drm_dp_mst_port. However, after destroying things we send a hotplug through (*mgr->cbs->hotplug)(mgr) which is where the problems start. For i915, this calls all the way down to the fbcon probing helpers, which start trying to access the port in a modeset. [ 45.062001] ================================================================== [ 45.062112] BUG: KASAN: use-after-free in ex_handler_refcount+0x146/0x180 [ 45.062196] Write of size 4 at addr ffff8882b4b70968 by task kworker/3:1/53 [ 45.062325] CPU: 3 PID: 53 Comm: kworker/3:1 Kdump: loaded Tainted: G O 4.20.0-rc4Lyude-Test+ #3 [ 45.062442] Hardware name: LENOVO 20BWS1KY00/20BWS1KY00, BIOS JBET71WW (1.35 ) 09/14/2018 [ 45.062554] Workqueue: events drm_dp_destroy_connector_work [drm_kms_helper] [ 45.062641] Call Trace: [ 45.062685] dump_stack+0xbd/0x15a [ 45.062735] ? dump_stack_print_info.cold.0+0x1b/0x1b [ 45.062801] ? printk+0x9f/0xc5 [ 45.062847] ? kmsg_dump_rewind_nolock+0xe4/0xe4 [ 45.062909] ? ex_handler_refcount+0x146/0x180 [ 45.062970] print_address_description+0x71/0x239 [ 45.063036] ? ex_handler_refcount+0x146/0x180 [ 45.063095] kasan_report.cold.5+0x242/0x30b [ 45.063155] __asan_report_store4_noabort+0x1c/0x20 [ 45.063313] ex_handler_refcount+0x146/0x180 [ 45.063371] ? ex_handler_clear_fs+0xb0/0xb0 [ 45.063428] fixup_exception+0x98/0xd7 [ 45.063484] ? raw_notifier_call_chain+0x20/0x20 [ 45.063548] do_trap+0x6d/0x210 [ 45.063605] ? _GLOBAL__sub_I_65535_1_drm_dp_aux_unregister_devnode+0x2f/0x1c6 [drm_kms_helper] [ 45.063732] do_error_trap+0xc0/0x170 [ 45.063802] ? _GLOBAL__sub_I_65535_1_drm_dp_aux_unregister_devnode+0x2f/0x1c6 [drm_kms_helper] [ 45.063929] do_invalid_op+0x3b/0x50 [ 45.063997] ? _GLOBAL__sub_I_65535_1_drm_dp_aux_unregister_devnode+0x2f/0x1c6 [drm_kms_helper] [ 45.064103] invalid_op+0x14/0x20 [ 45.064162] RIP: 0010:_GLOBAL__sub_I_65535_1_drm_dp_aux_unregister_devnode+0x2f/0x1c6 [drm_kms_helper] [ 45.064274] Code: 00 48 c7 c7 80 fe 53 a0 48 89 e5 e8 5b 6f 26 e1 5d c3 48 8d 0e 0f 0b 48 8d 0b 0f 0b 48 8d 0f 0f 0b 48 8d 0f 0f 0b 49 8d 4d 00 <0f> 0b 49 8d 0e 0f 0b 48 8d 08 0f 0b 49 8d 4d 00 0f 0b 48 8d 0b 0f [ 45.064569] RSP: 0018:ffff8882b789ee10 EFLAGS: 00010282 [ 45.064637] RAX: ffff8882af47ae70 RBX: ffff8882af47aa60 RCX: ffff8882b4b70968 [ 45.064723] RDX: ffff8882af47ae70 RSI: 0000000000000008 RDI: ffff8882b788bdb8 [ 45.064808] RBP: ffff8882b789ee28 R08: ffffed1056f13db4 R09: ffffed1056f13db3 [ 45.064894] R10: ffffed1056f13db3 R11: ffff8882b789ed9f R12: ffff8882af47ad28 [ 45.064980] R13: ffff8882b4b70968 R14: ffff8882acd86728 R15: ffff8882b4b75dc8 [ 45.065084] drm_dp_mst_reset_vcpi_slots+0x12/0x80 [drm_kms_helper] [ 45.065225] intel_mst_disable_dp+0xda/0x180 [i915] [ 45.065361] intel_encoders_disable.isra.107+0x197/0x310 [i915] [ 45.065498] haswell_crtc_disable+0xbe/0x400 [i915] [ 45.065622] ? i9xx_disable_plane+0x1c0/0x3e0 [i915] [ 45.065750] intel_atomic_commit_tail+0x74e/0x3e60 [i915] [ 45.065884] ? intel_pre_plane_update+0xbc0/0xbc0 [i915] [ 45.065968] ? drm_atomic_helper_swap_state+0x88b/0x1d90 [drm_kms_helper] [ 45.066054] ? kasan_check_write+0x14/0x20 [ 45.066165] ? i915_gem_track_fb+0x13a/0x330 [i915] [ 45.066277] ? i915_sw_fence_complete+0xe9/0x140 [i915] [ 45.066406] ? __i915_sw_fence_complete+0xc50/0xc50 [i915] [ 45.066540] intel_atomic_commit+0x72e/0xef0 [i915] [ 45.066635] ? drm_dev_dbg+0x200/0x200 [drm] [ 45.066764] ? intel_atomic_commit_tail+0x3e60/0x3e60 [i915] [ 45.066898] ? intel_atomic_commit_tail+0x3e60/0x3e60 [i915] [ 45.067001] drm_atomic_commit+0xc4/0xf0 [drm] [ 45.067074] restore_fbdev_mode_atomic+0x562/0x780 [drm_kms_helper] [ 45.067166] ? drm_fb_helper_debug_leave+0x690/0x690 [drm_kms_helper] [ 45.067249] ? kasan_check_read+0x11/0x20 [ 45.067324] restore_fbdev_mode+0x127/0x4b0 [drm_kms_helper] [ 45.067364] ? kasan_check_read+0x11/0x20 [ 45.067406] drm_fb_helper_restore_fbdev_mode_unlocked+0x164/0x200 [drm_kms_helper] [ 45.067462] ? drm_fb_helper_hotplug_event+0x30/0x30 [drm_kms_helper] [ 45.067508] ? kasan_check_write+0x14/0x20 [ 45.070360] ? mutex_unlock+0x22/0x40 [ 45.073748] drm_fb_helper_set_par+0xb2/0xf0 [drm_kms_helper] [ 45.075846] drm_fb_helper_hotplug_event.part.33+0x1cd/0x290 [drm_kms_helper] [ 45.078088] drm_fb_helper_hotplug_event+0x1c/0x30 [drm_kms_helper] [ 45.082614] intel_fbdev_output_poll_changed+0x9f/0x140 [i915] [ 45.087069] drm_kms_helper_hotplug_event+0x67/0x90 [drm_kms_helper] [ 45.089319] intel_dp_mst_hotplug+0x37/0x50 [i915] [ 45.091496] drm_dp_destroy_connector_work+0x510/0x6f0 [drm_kms_helper] [ 45.093675] ? drm_dp_update_payload_part1+0x1220/0x1220 [drm_kms_helper] [ 45.095851] ? kasan_check_write+0x14/0x20 [ 45.098473] ? kasan_check_read+0x11/0x20 [ 45.101155] ? strscpy+0x17c/0x530 [ 45.103808] ? __switch_to_asm+0x34/0x70 [ 45.106456] ? syscall_return_via_sysret+0xf/0x7f [ 45.109711] ? read_word_at_a_time+0x20/0x20 [ 45.113138] ? __switch_to_asm+0x40/0x70 [ 45.116529] ? __switch_to_asm+0x34/0x70 [ 45.119891] ? __switch_to_asm+0x40/0x70 [ 45.123224] ? __switch_to_asm+0x34/0x70 [ 45.126540] ? __switch_to_asm+0x34/0x70 [ 45.129824] process_one_work+0x88d/0x15d0 [ 45.133172] ? pool_mayday_timeout+0x850/0x850 [ 45.136459] ? pci_mmcfg_check_reserved+0x110/0x128 [ 45.139739] ? wake_q_add+0xb0/0xb0 [ 45.143010] ? check_preempt_wakeup+0x652/0x1050 [ 45.146304] ? worker_enter_idle+0x29e/0x740 [ 45.149589] ? __schedule+0x1ec0/0x1ec0 [ 45.152937] ? kasan_check_read+0x11/0x20 [ 45.156179] ? _raw_spin_lock_irq+0xa3/0x130 [ 45.159382] ? _raw_read_unlock_irqrestore+0x30/0x30 [ 45.162542] ? kasan_check_write+0x14/0x20 [ 45.165657] worker_thread+0x1a5/0x1470 [ 45.168725] ? set_load_weight+0x2e0/0x2e0 [ 45.171755] ? process_one_work+0x15d0/0x15d0 [ 45.174806] ? __switch_to_asm+0x34/0x70 [ 45.177645] ? __switch_to_asm+0x40/0x70 [ 45.180323] ? __switch_to_asm+0x34/0x70 [ 45.182936] ? __switch_to_asm+0x40/0x70 [ 45.185539] ? __switch_to_asm+0x34/0x70 [ 45.188100] ? __switch_to_asm+0x40/0x70 [ 45.190628] ? __schedule+0x7d4/0x1ec0 [ 45.193143] ? save_stack+0xa9/0xd0 [ 45.195632] ? kasan_check_write+0x10/0x20 [ 45.198162] ? kasan_kmalloc+0xc4/0xe0 [ 45.200609] ? kmem_cache_alloc_trace+0xdd/0x190 [ 45.203046] ? kthread+0x9f/0x3b0 [ 45.205470] ? ret_from_fork+0x35/0x40 [ 45.207876] ? unwind_next_frame+0x43/0x50 [ 45.210273] ? __save_stack_trace+0x82/0x100 [ 45.212658] ? deactivate_slab.isra.67+0x3d4/0x580 [ 45.215026] ? default_wake_function+0x35/0x50 [ 45.217399] ? kasan_check_read+0x11/0x20 [ 45.219825] ? _raw_spin_lock_irqsave+0xae/0x140 [ 45.222174] ? __lock_text_start+0x8/0x8 [ 45.224521] ? replenish_dl_entity.cold.62+0x4f/0x4f [ 45.226868] ? __kthread_parkme+0x87/0xf0 [ 45.229200] kthread+0x2f7/0x3b0 [ 45.231557] ? process_one_work+0x15d0/0x15d0 [ 45.233923] ? kthread_park+0x120/0x120 [ 45.236249] ret_from_fork+0x35/0x40 [ 45.240875] Allocated by task 242: [ 45.243136] save_stack+0x43/0xd0 [ 45.245385] kasan_kmalloc+0xc4/0xe0 [ 45.247597] kmem_cache_alloc_trace+0xdd/0x190 [ 45.249793] drm_dp_add_port+0x1e0/0x2170 [drm_kms_helper] [ 45.252000] drm_dp_send_link_address+0x4a7/0x740 [drm_kms_helper] [ 45.254389] drm_dp_check_and_send_link_address+0x1a7/0x210 [drm_kms_helper] [ 45.256803] drm_dp_mst_link_probe_work+0x6f/0xb0 [drm_kms_helper] [ 45.259200] process_one_work+0x88d/0x15d0 [ 45.261597] worker_thread+0x1a5/0x1470 [ 45.264038] kthread+0x2f7/0x3b0 [ 45.266371] ret_from_fork+0x35/0x40 [ 45.270937] Freed by task 53: [ 45.273170] save_stack+0x43/0xd0 [ 45.275382] __kasan_slab_free+0x139/0x190 [ 45.277604] kasan_slab_free+0xe/0x10 [ 45.279826] kfree+0x99/0x1b0 [ 45.282044] drm_dp_free_mst_port+0x4a/0x60 [drm_kms_helper] [ 45.284330] drm_dp_destroy_connector_work+0x43e/0x6f0 [drm_kms_helper] [ 45.286660] process_one_work+0x88d/0x15d0 [ 45.288934] worker_thread+0x1a5/0x1470 [ 45.291231] kthread+0x2f7/0x3b0 [ 45.293547] ret_from_fork+0x35/0x40 [ 45.298206] The buggy address belongs to the object at ffff8882b4b70968 which belongs to the cache kmalloc-2k of size 2048 [ 45.303047] The buggy address is located 0 bytes inside of 2048-byte region [ffff8882b4b70968, ffff8882b4b71168) [ 45.308010] The buggy address belongs to the page: [ 45.310477] page:ffffea000ad2dc00 count:1 mapcount:0 mapping:ffff8882c080cf40 index:0x0 compound_mapcount: 0 [ 45.313051] flags: 0x8000000000010200(slab\|head) [ 45.315635] raw: 8000000000010200 ffffea000aac2808 ffffea000abe8608 ffff8882c080cf40 [ 45.318300] raw: 0000000000000000 00000000000d000d 00000001ffffffff 0000000000000000 [ 45.320966] page dumped because: kasan: bad access detected [ 45.326312] Memory state around the buggy address: [ 45.329085] ffff8882b4b70800: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 45.331845] ffff8882b4b70880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 45.334584] >ffff8882b4b70900: fc fc fc fc fc fc fc fc fc fc fc fc fc fb fb fb [ 45.337302] ^ [ 45.340061] ffff8882b4b70980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 45.342910] ffff8882b4b70a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 45.345748] ================================================================== So, this definitely isn't a fix that we want. This being said; there's no real easy fix for this problem because of some of the catch-22's of the MST helpers current design. For starters; we always need to validate a port with drm_dp_get_validated_port_ref(), but validation relies on the lifetime of the port in the actual topology. So once the port is gone, it can't be validated again. If we were to try to make the payload helpers not use port validation, then we'd cause another problem: if the port isn't validated, it could be freed and we'd just start causing more KASAN issues. There are already hacks that attempt to workaround this in drm_dp_mst_destroy_connector_work() by re-initializing the kref so that it can be used again and it's memory can be freed once the VCPI helpers finish removing the port's respective payloads. But none of these really do anything helpful since the port still can't be validated since it's gone from the topology. Also, that workaround is immensely confusing to read through. What really needs to be done in order to fix this is to teach DRM how to track the lifetime of the structs for MST ports and branch devices separately from their lifetime in the actual topology. Simply put; this means having two different krefs-one that removes the port/branch device from the topology, and one that finally calls kfree(). This would let us simplify things, since we'd now be able to keep ports around without having to keep them in the topology at the same time, which is exactly what we need in order to teach our VCPI helpers to only validate ports when it's actually necessary without running the risk of trying to use unallocated memory. Such a fix is on it's way, but for now let's play it safe and just revert this. If this bug has been around for well over a year, we can wait a little while to get an actual proper fix here. Signed-off-by: Lyude Paul <lyude@redhat.com> Fixes: `c54c7374ff` ("drm/dp_mst: Skip validating ports during destruction, just ref") Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Sean Paul <sean@poorly.run> Cc: Jerry Zuo <Jerry.Zuo@amd.com> Cc: Harry Wentland <Harry.Wentland@amd.com> Cc: stable@vger.kernel.org # v4.6+ Acked-by: Sean Paul <sean@poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20181128210005.24434-1-lyude@redhat.com		2018-11-28 16:22:17 -05:00
Documentation	XArray updates for 4.20-rc4	2018-11-24 18:44:01 -08:00
LICENSES	This is a fairly typical cycle for documentation. There's some welcome	2018-10-24 18:01:11 +01:00
arch	arm64 fixes:	2018-11-24 09:42:32 -08:00
block	SCSI: fix queue cleanup race before queue initialization is done	2018-11-14 08:19:10 -07:00
certs	export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR()	2018-08-22 23:21:44 +09:00
crypto	crypto: user - Zeroize whole structure given to user space	2018-11-09 17:35:43 +08:00
drivers	Revert "drm/dp_mst: Skip validating ports during destruction, just ref"	2018-11-28 16:22:17 -05:00
firmware	kbuild: remove all dummy assignments to obj-	2017-11-18 11:46:06 +09:00
fs	NFS client bugfixes for Linux 4.20	2018-11-25 09:19:58 -08:00
include	Two dma-direct / swiotlb regressions fixes	2018-11-25 09:24:40 -08:00
init	memblock: stop using implicit alignment to SMP_CACHE_BYTES	2018-10-31 08:54:16 -07:00
ipc	ipc: IPCMNI limit check for semmni	2018-10-31 08:54:14 -07:00
kernel	swiotlb: Skip cache maintenance on map error	2018-11-21 18:47:58 +01:00
lib	XArray updates for 4.20-rc4	2018-11-24 18:44:01 -08:00
mm	mm/memblock.c: fix a typo in __next_mem_pfn_range() comments	2018-11-18 10:15:10 -08:00
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2018-11-24 09:19:38 -08:00
samples	VFIO updates for v4.20	2018-10-31 11:01:38 -07:00
scripts	scripts/spdxcheck.py: make python3 compliant	2018-11-18 10:15:10 -08:00
security	selinux/stable-4.20 PR 20181115	2018-11-15 11:26:09 -06:00
sound	ALSA: hda/ca0132 - fix AE-5 pincfg	2018-11-19 12:18:43 +01:00
tools	Power management fixes for 4.20-rc4	2018-11-23 10:52:57 -08:00
usr	initramfs: move gen_initramfs_list.sh from scripts/ to usr/	2018-08-22 23:21:44 +09:00
virt	Revert "mm, mmu_notifier: annotate mmu notifiers with blockable invalidate callbacks"	2018-10-26 16:25:19 -07:00
.clang-format	page cache: Convert find_get_pages_contig to XArray	2018-10-21 10:46:34 -04:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	…
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	Kbuild updates for v4.17 (2nd)	2018-04-15 17:21:30 -07:00
.mailmap	mailmap: Update email for Punit Agrawal	2018-11-05 10:02:11 +00:00
COPYING	COPYING: use the new text with points to the license files	2018-03-23 12:41:45 -06:00
CREDITS	MAINTAINERS: change Sparse's maintainer	2018-11-25 09:17:43 -08:00
Kbuild	Kbuild updates for v4.15	2017-11-17 17:45:29 -08:00
Kconfig	kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt	2018-08-02 08:06:55 +09:00
MAINTAINERS	MAINTAINERS: change Sparse's maintainer	2018-11-25 09:17:43 -08:00
Makefile	Linux 4.20-rc4	2018-11-25 14:19:31 -08:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.