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Chris Wilson b7c6646117 drm/i915/display: Check for an LPSP encoder before dereferencing
Avoid a GPF at

<1>[   20.177320] BUG: kernel NULL pointer dereference, address: 000000000000007c
<1>[   20.177322] #PF: supervisor read access in kernel mode
<1>[   20.177323] #PF: error_code(0x0000) - not-present page
<6>[   20.177324] PGD 0 P4D 0
<4>[   20.177327] Oops: 0000 [#1] PREEMPT SMP PTI
<4>[   20.177328] CPU: 1 PID: 944 Comm: debugfs_test Not tainted 5.8.0-rc7-CI-CI_DRM_8814+ #1
<4>[   20.177330] Hardware name: Dell Inc. XPS 13 9360/0823VW, BIOS 2.9.0 07/09/2018
<4>[   20.177372] RIP: 0010:i915_lpsp_capability_show+0x44/0xc0 [i915]
<4>[   20.177374] Code: 0f b6 81 ca 0d 00 00 3c 0b 74 77 76 19 3c 0c 75 44 83 7e 7c 01 7e 2f 48 c7 c6 d7 b9 47 a0 e8 43 df 06 e1 31 c0 c3 3c 09 72 2b <8b> 46 7c 85 c0 75 e6 8b 82 e4 00 00 00 89 c2 83 e2 fb 83 fa 0a 74
<4>[   20.177376] RSP: 0018:ffffc90000cebe38 EFLAGS: 00010246
<4>[   20.177377] RAX: 0000000000000009 RBX: ffff888267fe6a58 RCX: ffff888252d10000
<4>[   20.177378] RDX: ffff88824a9a4000 RSI: 0000000000000000 RDI: ffff888267fe6a30
<4>[   20.177379] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
<4>[   20.177380] R10: 0000000000000001 R11: 0000000000000000 R12: ffffc90000cebf08
<4>[   20.177381] R13: 00000000ffffffff R14: 0000000000000001 R15: ffff888267fe6a30
<4>[   20.177383] FS:  00007f6f9c6b5e40(0000) GS:ffff888276480000(0000) knlGS:0000000000000000
<4>[   20.177384] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[   20.177385] CR2: 000000000000007c CR3: 0000000255f04006 CR4: 00000000003606e0
<4>[   20.177386] Call Trace:
<4>[   20.177390]  seq_read+0xcb/0x420

which is presumably from having no encoder attached at that time.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2175
Fixes: 8806211fe7 ("drm/i915: Add i915_lpsp_capability debugfs")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200729130912.30093-1-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit a22b1a9bb0)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
2020-08-19 15:23:13 +03:00
Documentation Misc fixes and small updates all around the place: 2020-08-15 10:38:03 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch parisc: fix PMD pages allocation by restoring pmd_alloc_one() 2020-08-16 10:53:13 -07:00
block block-5.9-2020-08-14 2020-08-15 20:36:42 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-14 13:09:15 -07:00
drivers drm/i915/display: Check for an LPSP encoder before dereferencing 2020-08-19 15:23:13 +03:00
fs io_uring-5.9-2020-08-15 2020-08-16 10:55:12 -07:00
include io_uring-5.9-2020-08-15 2020-08-16 10:55:12 -07:00
init OpenRISC updates for 5.9 2020-08-14 14:04:53 -07:00
ipc ipc/shm.c: remove the superfluous break 2020-08-12 10:58:02 -07:00
kernel io_uring-5.9-2020-08-15 2020-08-16 10:55:12 -07:00
lib iomap: constify ioreadX() iomem argument (as in generic implementation) 2020-08-14 19:56:57 -07:00
mm Merge branch 'akpm' (patches from Andrew) 2020-08-15 08:02:03 -07:00
net 9p pull request for inclusion in 5.9 2020-08-15 08:34:36 -07:00
samples Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
scripts Kconfig updates for v5.9 2020-08-14 11:04:45 -07:00
security Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
sound sound fixes for 5.9-rc1 2020-08-14 15:58:57 -07:00
tools Cleanup, SECCOMP_FILTER support, message printing fixes, and other 2020-08-15 18:50:32 -07:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap mailmap: add entry for Greg Kurz 2020-08-14 19:56:56 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS perf tools changes for v5.9: 2nd batch 2020-08-15 11:17:15 -07:00
Makefile Linux 5.9-rc1 2020-08-16 13:04:57 -07:00
README

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.