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Hans Verkuil ac34b79da1 media: v4l2-ctrls: fix reference to freed memory 
When controls are used together with the Request API, then for
each request a v4l2_ctrl_handler struct is allocated. This contains
the controls that can be set in a request. If a control is *not* set in
the request, then the value used in the most recent previous request
must be used, or the current value if it is not found in any outstanding
requests.

The framework tried to find such a previous request and it would set
the 'req' pointer in struct v4l2_ctrl_ref to the v4l2_ctrl_ref of the
control in such a previous request. So far, so good. However, when that
previous request was applied to the hardware, returned to userspace, and
then userspace would re-init or free that request, any 'ref' pointer in
still-queued requests would suddenly point to freed memory.

This was not noticed before since the drivers that use this expected
that each request would always have the controls set, so there was
never any need to find a control in older requests. This requirement
was relaxed, and now this bug surfaced.

It was also made worse by changeset
2fae4d6aab ("media: v4l2-ctrls: v4l2_ctrl_request_complete() should always set ref->req")
which increased the chance of this happening.

The use of the 'req' pointer in v4l2_ctrl_ref was very fragile, so
drop this entirely. Instead add a valid_p_req bool to indicate that
p_req contains a valid value for this control. And if it is false,
then just use the current value of the control.

Note that VIDIOC_G_EXT_CTRLS will always return -EACCES when attempting
to get a control from a request until the request is completed. And in
that case, all controls in the request will have the control value set
(i.e. valid_p_req is true). This means that the whole 'find the most
recent previous request containing a control' idea is pointless, and
the code can be simplified considerably.

The v4l2_g_ext_ctrls_common() function was refactored a bit to make
it more understandable. It also avoids updating volatile controls
in a completed request since that was already done when the request
was completed.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 2fae4d6aab ("media: v4l2-ctrls: v4l2_ctrl_request_complete() should always set ref->req")
Fixes: 6fa6f831f0 ("media: v4l2-ctrls: add core request support")
Cc: <stable@vger.kernel.org>      # for v5.9 and up
Tested-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
History 2021-04-15 13:18:09 +02:00
arch * Doc fixes 2021-03-04 11:26:17 -08:00
block block/bfq: update comments and default value in docs for fifo_expire 2021-03-02 11:25:38 -07:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto Keyrings miscellany 2021-02-23 16:09:23 -08:00
Documentation media: dt-bindings: media: IR: Add H616 IR compatible string 2021-04-09 13:03:56 +02:00
drivers media: v4l2-ctrls: fix reference to freed memory 2021-04-15 13:18:09 +02:00
fs pstore fixes for v5.12-rc2 2021-03-05 17:21:25 -08:00
include media: v4l2-ctrls: fix reference to freed memory 2021-04-15 13:18:09 +02:00
init kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO 2021-02-28 15:19:21 +09:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel io_uring-5.12-2021-03-05 2021-03-05 12:44:43 -08:00
lib Merge branch 'kmap-conversion-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux 2021-03-01 11:24:18 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm swap: fix swapfile read/write offset 2021-03-02 17:25:46 -07:00
net io_uring-worker.v3-2021-02-25 2021-02-27 08:29:02 -08:00
samples treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
scripts gcc-plugins fixes for v5.12-rc2 2021-03-05 17:23:03 -08:00
security Keyrings miscellany 2021-02-23 16:09:23 -08:00
sound ALSA: hda/realtek: Apply dual codec quirks for MSI Godlike X570 board 2021-03-03 15:25:03 +01:00
tools doc: update rcu_dereference.rst reference 2021-04-06 14:45:04 +02:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
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 MAINTAINERS: update ovti,ov2680.yaml reference 2021-04-07 10:01:07 +02:00
Makefile Linux 5.12-rc2 2021-03-05 17:33:41 -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.