6cb304b312
If the ips module calls into the driver during an unbind/bind cycle, we may see the driver while it has unregistered itself from ips and try and dereference a NULL ips_mchdev pointer. <1> [211.928844] BUG: kernel NULL pointer dereference, address: 0000000000000014 <1> [211.928861] #PF: supervisor read access in kernel mode <1> [211.928871] #PF: error_code(0x0000) - not-present page <6> [211.928881] PGD 0 P4D 0 <4> [211.928890] Oops: 0000 [#1] PREEMPT SMP PTI <4> [211.928900] CPU: 3 PID: 327 Comm: ips-monitor Not tainted 5.9.0-rc5-CI-CI_DRM_9008+ #1 <4> [211.928914] Hardware name: Hewlett-Packard HP EliteBook 8440p/172A, BIOS 68CCU Ver. F.24 09/13/2013 <4> [211.929056] RIP: 0010:mchdev_get+0x5a/0x180 [i915] <4> [211.929067] Code: c0 5a 74 0d 80 3d f1 53 29 00 00 0f 84 ab 00 00 00 48 8b 1d c8 a8 29 00 e8 d3 18 89 e1 85 c0 74 09 80 3d d1 53 29 00 00 74 65 <8b> 4b 14 48 8d 7b 14 85 c9 0f 84 09 01 00 00 8d 51 01 89 c8 f0 0f <4> [211.929095] RSP: 0018:ffffc900002efe60 EFLAGS: 00010202 <4> [211.929105] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffff8881297acf40 <4> [211.929118] RDX: 0000000000000000 RSI: ffffffff8264e2c0 RDI: ffff8881297ad820 <4> [211.929130] RBP: ffffc900002efe68 R08: ffff8881297ad820 R09: 00000000fffffffe <4> [211.929143] R10: ffff8881297acf40 R11: 00000000fff74c96 R12: ffff8881294dfa18 <4> [211.929155] R13: 0000000000000067 R14: ffff888126eff640 R15: ffff888126efe840 <4> [211.929168] FS: 0000000000000000(0000) GS:ffff888133d80000(0000) knlGS:0000000000000000 <4> [211.929182] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 <4> [211.929194] CR2: 0000000000000014 CR3: 0000000002610000 CR4: 00000000000006e0 <4> [211.929206] Call Trace: <4> [211.929294] i915_read_mch_val+0x15/0x380 [i915] <4> [211.929309] ? ips_monitor+0x3fb/0x630 [intel_ips] <4> [211.929321] ips_monitor+0x53c/0x630 [intel_ips] <4> [211.929334] ? ips_gpu_lower+0x30/0x30 [intel_ips] <4> [211.929348] kthread+0x14d/0x170 <4> [211.929358] ? kthread_park+0x80/0x80 <4> [211.929369] ret_from_fork+0x22/0x30 <4> [211.929382] Modules linked in: vgem snd_hda_codec_hdmi snd_hda_codec_generic ledtrig_audio i915 coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hwdep snd_hda_core e1000e snd_pcm mei_me mei intel_ips lpc_ich ptp prime_numbers pps_core <4> [211.929437] CR2: 0000000000000014 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20200915105113.26564-1-chris@chris-wilson.co.uk
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.