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Daniel Vetter e4a0e09b79 drm/atomic: Fix potential use-after-free in nonblocking commits 
commit 4e076c73e4 upstream.

This requires a bit of background.  Properly done a modeset driver's
unload/remove sequence should be

	drm_dev_unplug();
	drm_atomic_helper_shutdown();
	drm_dev_put();

The trouble is that the drm_dev_unplugged() checks are by design racy,
they do not synchronize against all outstanding ioctl.  This is because
those ioctl could block forever (both for modeset and for driver
specific ioctls), leading to deadlocks in hotunplug.  Instead the code
sections that touch the hardware need to be annotated with
drm_dev_enter/exit, to avoid accessing hardware resources after the
unload/remove has finished.

To avoid use-after-free issues all the involved userspace visible
objects are supposed to hold a reference on the underlying drm_device,
like drm_file does.

The issue now is that we missed one, the atomic modeset ioctl can be run
in a nonblocking fashion, and in that case it cannot rely on the implied
drm_device reference provided by the ioctl calling context.  This can
result in a use-after-free if an nonblocking atomic commit is carefully
raced against a driver unload.

Fix this by unconditionally grabbing a drm_device reference for any
drm_atomic_state structures.  Strictly speaking this isn't required for
blocking commits and TEST_ONLY calls, but it's the simpler approach.

Thanks to shanzhulig for the initial idea of grabbing an unconditional
reference, I just added comments, a condensed commit message and fixed a
minor potential issue in where exactly we drop the final reference.

Reported-by: shanzhulig <shanzhulig@gmail.com>
Suggested-by: shanzhulig <shanzhulig@gmail.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-07-23 13:49:50 +02:00
arch MIPS: kvm: Fix build error with KVM_MIPS_DEBUG_COP0_COUNTERS enabled 2023-07-23 13:49:50 +02:00
block blk-crypto: use dynamic lock class for blk_crypto_profile::lock 2023-07-23 13:49:21 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:21:42 +02:00
Documentation dm init: add dm-mod.waitfor to wait for asynchronously probed block devices 2023-07-23 13:49:38 +02:00
drivers drm/atomic: Fix potential use-after-free in nonblocking commits 2023-07-23 13:49:50 +02:00
fs cifs: if deferred close is disabled then close files immediately 2023-07-23 13:49:45 +02:00
include fprobe: Ensure running fprobe_exit_handler() finished before calling rethook_free() 2023-07-23 13:49:46 +02:00
init gcc: disable '-Warray-bounds' for gcc-13 too 2023-04-26 14:28:43 +02:00
io_uring io_uring: Use io_schedule* in cqring wait 2023-07-19 16:22:18 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel swiotlb: mark swiotlb_memblock_alloc() as __init 2023-07-23 13:49:50 +02:00
lib lib/bitmap: drop optimization of bitmap_{from,to}_arr64 2023-07-19 16:21:58 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm kasan: add kasan_tag_mismatch prototype 2023-07-23 13:49:32 +02:00
net net/sched: sch_qfq: reintroduce lmax bound check for MTU 2023-07-23 13:49:50 +02:00
rust rust: kernel: Mark rust_fmt_argument as extern "C" 2023-04-26 14:28:38 +02:00
samples samples: ftrace: Save required argument registers in sample trampolines 2023-07-23 13:49:44 +02:00
scripts kbuild: Disable GCOV for *.mod.o 2023-07-19 16:21:44 +02:00
security integrity: Fix possible multiple allocation in integrity_inode_get() 2023-07-19 16:22:11 +02:00
sound ASoC: mediatek: mt8173: Fix snd_soc_component_initialize error path 2023-07-19 16:22:14 +02:00
tools selftests: mptcp: pm_nl_ctl: fix 32-bit support 2023-07-23 13:49:47 +02:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Avoid illegal stage2 mapping on invalid memory slot 2023-06-28 11:12:23 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS smb: move client and server files to common directory fs/smb 2023-06-28 11:12:40 +02:00
Makefile Linux 6.1.39 2023-07-19 16:22:18 +02:00
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.