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Alexander Mikhalitsyn 8619236d93 shm: extend forced shm destroy to support objects from several IPC nses 
commit 85b6d24646 upstream.

Currently, the exit_shm() function not designed to work properly when
task->sysvshm.shm_clist holds shm objects from different IPC namespaces.

This is a real pain when sysctl kernel.shm_rmid_forced = 1, because it
leads to use-after-free (reproducer exists).

This is an attempt to fix the problem by extending exit_shm mechanism to
handle shm's destroy from several IPC ns'es.

To achieve that we do several things:

1. add a namespace (non-refcounted) pointer to the struct shmid_kernel

2. during new shm object creation (newseg()/shmget syscall) we
   initialize this pointer by current task IPC ns

3. exit_shm() fully reworked such that it traverses over all shp's in
   task->sysvshm.shm_clist and gets IPC namespace not from current task
   as it was before but from shp's object itself, then call
   shm_destroy(shp, ns).

Note: We need to be really careful here, because as it was said before
(1), our pointer to IPC ns non-refcnt'ed.  To be on the safe side we
using special helper get_ipc_ns_not_zero() which allows to get IPC ns
refcounter only if IPC ns not in the "state of destruction".

Q/A

Q: Why can we access shp->ns memory using non-refcounted pointer?
A: Because shp object lifetime is always shorther than IPC namespace
   lifetime, so, if we get shp object from the task->sysvshm.shm_clist
   while holding task_lock(task) nobody can steal our namespace.

Q: Does this patch change semantics of unshare/setns/clone syscalls?
A: No. It's just fixes non-covered case when process may leave IPC
   namespace without getting task->sysvshm.shm_clist list cleaned up.

Link: https://lkml.kernel.org/r/67bb03e5-f79c-1815-e2bf-949c67047418@colorfullife.com
Link: https://lkml.kernel.org/r/20211109151501.4921-1-manfred@colorfullife.com
Fixes: ab602f7991 ("shm: make exit_shm work proportional to task activity")
Co-developed-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-12-08 08:46:53 +01:00
arch hugetlbfs: flush TLBs correctly after huge_pmd_unshare 2021-12-08 08:46:52 +01:00
block blk-throttle: fix UAF by deleteing timer in blk_throtl_exit() 2021-09-26 13:37:30 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-22 11:45:19 +02:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-26 11:40:32 +01:00
Documentation pinctrl: armada-37xx: Correct PWM pins definitions 2021-12-08 08:46:51 +01:00
drivers tty: hvc: replace BUG_ON() with negative return value 2021-12-08 08:46:53 +01:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:20:30 +01:00
fs fuse: release pipe buf after last use 2021-12-08 08:46:52 +01:00
include shm: extend forced shm destroy to support objects from several IPC nses 2021-12-08 08:46:53 +01:00
init pid: take a reference when initializing cad_pid 2021-06-10 12:43:51 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-08 08:46:53 +01:00
kernel tracing: Check pid filtering when creating events 2021-12-08 08:46:49 +01:00
lib lib/xz: Validate the value before assigning it to an enum variable 2021-11-26 11:40:28 +01:00
mm hugetlbfs: flush TLBs correctly after huge_pmd_unshare 2021-12-08 08:46:52 +01:00
net NFC: add NCI_UNREG flag to eliminate the race 2021-12-08 08:46:52 +01:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-26 11:40:31 +01:00
scripts leaking_addresses: Always print a trailing newline 2021-11-26 11:40:28 +01:00
security apparmor: fix error check 2021-11-26 11:40:34 +01:00
sound ASoC: topology: Add missing rwsem around snd_ctl_remove() calls 2021-12-08 08:46:48 +01:00
tools usb: testusb: Fix for showing the connection speed 2021-10-09 14:09:46 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:34:19 +02:00
virt KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped() 2021-08-08 08:53:29 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 16:36:12 +01:00
Makefile Linux 4.14.256 2021-11-26 11:40:42 +01:00
README

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.