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Mike Rapoport 2176441fdd userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK 
[ Upstream commit 3c1c24d91f ]

A while ago Andy noticed
(http://lkml.kernel.org/r/CALCETrWY+5ynDct7eU_nDUqx=okQvjm=Y5wJvA4ahBja=CQXGw@mail.gmail.com)
that UFFD_FEATURE_EVENT_FORK used by an unprivileged user may have
security implications.

As the first step of the solution the following patch limits the availably
of UFFD_FEATURE_EVENT_FORK only for those having CAP_SYS_PTRACE.

The usage of CAP_SYS_PTRACE ensures compatibility with CRIU.

Yet, if there are other users of non-cooperative userfaultfd that run
without CAP_SYS_PTRACE, they would be broken :(

Current implementation of UFFD_FEATURE_EVENT_FORK modifies the file
descriptor table from the read() implementation of uffd, which may have
security implications for unprivileged use of the userfaultfd.

Limit availability of UFFD_FEATURE_EVENT_FORK only for callers that have
CAP_SYS_PTRACE.

Link: http://lkml.kernel.org/r/1572967777-8812-2-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Daniel Colascione <dancol@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Nick Kralevich <nnk@google.com>
Cc: Nosh Minwalla <nosh@google.com>
Cc: Pavel Emelyanov <ovzxemul@gmail.com>
Cc: Tim Murray <timmurray@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2020-01-04 19:18:32 +01:00
Documentation dt-bindings: Improve validation build error handling 2020-01-04 19:18:11 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch s390: disable preemption when switching to nodat stack with CALL_ON_STACK 2020-01-04 19:18:31 +01:00
block iocost: over-budget forced IOs should schedule async delay 2019-12-31 16:46:19 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto KEYS: asymmetric: return ENOMEM if akcipher_request_alloc() fails 2019-12-31 16:46:07 +01:00
drivers mailbox: imx: Fix Tx doorbell shutdown path 2020-01-04 19:18:30 +01:00
fs userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK 2020-01-04 19:18:32 +01:00
include libfdt: define INT32_MAX and UINT32_MAX in libfdt_env.h 2020-01-04 19:18:28 +01:00
init Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
ipc ipc/sem.c: convert to use built-in RCU list checking 2019-09-25 17:51:41 -07:00
kernel kernel: sysctl: make drop_caches write-only 2020-01-04 19:18:32 +01:00
lib ubsan, x86: Annotate and allow __ubsan_handle_shift_out_of_bounds() in uaccess regions 2019-12-31 16:44:25 +01:00
mm mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG 2019-12-31 16:46:07 +01:00
net can: j1939: j1939_sk_bind(): take priv after lock is held 2019-12-31 16:45:56 +01:00
samples samples: pktgen: fix proc_cmd command result check logic 2019-12-31 16:43:45 +01:00
scripts scripts/kallsyms: fix definitely-lost memory leak 2020-01-04 19:18:23 +01:00
security apparmor: fix unsigned len comparison with less than zero 2020-01-04 19:18:22 +01:00
sound ASoC: soc-pcm: check symmetry before hw_params 2019-12-31 16:45:42 +01:00
tools selftests: vm: add fragment CONFIG_TEST_VMALLOC 2020-01-04 19:18:31 +01:00
usr kbuild: update compile-test header list for v5.4-rc2 2019-10-05 15:29:49 +09:00
virt KVM: arm/arm64: Properly handle faulting of device mappings 2019-12-31 16:46:24 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.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: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-22 14:28:14 -08:00
Makefile Linux 5.4.7 2019-12-31 16:46:36 +01:00
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.