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Tadeusz Struk 13765de814 sched/fair: Fix fault in reweight_entity 
Syzbot found a GPF in reweight_entity. This has been bisected to
commit 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an invalid
sched_task_group")

There is a race between sched_post_fork() and setpriority(PRIO_PGRP)
within a thread group that causes a null-ptr-deref in
reweight_entity() in CFS. The scenario is that the main process spawns
number of new threads, which then call setpriority(PRIO_PGRP, 0, -20),
wait, and exit.  For each of the new threads the copy_process() gets
invoked, which adds the new task_struct and calls sched_post_fork()
for it.

In the above scenario there is a possibility that
setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread
in the group that is just being created by copy_process(), and for
which the sched_post_fork() has not been executed yet. This will
trigger a null pointer dereference in reweight_entity(), as it will
try to access the run queue pointer, which hasn't been set.

Before the mentioned change the cfs_rq pointer for the task  has been
set in sched_fork(), which is called much earlier in copy_process(),
before the new task is added to the thread_group.  Now it is done in
the sched_post_fork(), which is called after that.  To fix the issue
the remove the update_load param from the update_load param() function
and call reweight_task() only if the task flag doesn't have the
TASK_NEW flag set.

Fixes: 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")
Reported-by: syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220203161846.1160750-1-tadeusz.struk@linaro.org
2022-02-06 22:37:26 +01:00
arch - Add another Intel CPU model to the list of CPUs supporting the 2022-01-30 12:55:06 +02:00
block block: add bio_start_io_acct_time() to control start_time 2022-01-28 12:28:15 -07:00
certs certs: Fix build error when CONFIG_MODULE_SIG_KEY is empty 2022-01-23 00:08:44 +09:00
crypto lib/crypto: add prompts back to crypto libraries 2022-01-18 13:03:55 +01:00
Documentation - Drop an unused private data field in the AIC driver 2022-01-30 15:12:02 +02:00
drivers - Drop an unused private data field in the AIC driver 2022-01-30 15:12:02 +02:00
fs ocfs2: fix a deadlock when commit trans 2022-01-30 09:56:58 +02:00
include psi: fix "no previous prototype" warnings when CONFIG_CGROUPS=n 2022-01-30 09:56:58 +02:00
init lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() 2022-01-22 08:33:37 +02:00
ipc proc: remove PDE_DATA() completely 2022-01-22 08:33:37 +02:00
kernel sched/fair: Fix fault in reweight_entity 2022-02-06 22:37:26 +01:00
lib kasan: test: fix compatibility with FORTIFY_SOURCE 2022-01-30 09:56:58 +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 memory-failure: fetch compound_head after pgmap_pfn_valid() 2022-01-30 09:56:58 +02:00
net \n 2022-01-28 17:51:31 +02:00
samples Merge branch 'akpm' (patches from Andrew) 2022-01-20 10:41:01 +02:00
scripts ftrace: Have architectures opt-in for mcount build time sorting 2022-01-27 19:15:44 -05:00
security Fix NULL pointer crash in LSM via Ceph, from Vivek Goyal <vgoyal@redhat.com>. 2022-01-29 08:52:27 +02:00
sound proc: remove PDE_DATA() completely 2022-01-22 08:33:37 +02:00
tools tools/testing/scatterlist: add missing defines 2022-01-30 09:56:58 +02:00
usr kbuild: remove include/linux/cyclades.h from header file check 2022-01-27 08:51:08 +01:00
virt Two larger x86 series: 2022-01-28 19:00:26 +02:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update email address of Brian Silverman 2022-01-24 18:27:23 +01:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Removing Ohad from remoteproc/rpmsg maintenance 2021-12-08 10:09:40 -07:00
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 Networking fixes for 5.17-rc2, including fixes from netfilter and can. 2022-01-27 20:58:39 +02:00
Makefile Linux 5.17-rc2 2022-01-30 15:37:07 +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.