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Daniel Borkmann d8c3859870 bpf: Add lockdown check for probe_write_user helper 
commit 51e1bb9eea upstream.

Back then, commit 96ae522795 ("bpf: Add bpf_probe_write_user BPF helper
to be called in tracers") added the bpf_probe_write_user() helper in order
to allow to override user space memory. Its original goal was to have a
facility to "debug, divert, and manipulate execution of semi-cooperative
processes" under CAP_SYS_ADMIN. Write to kernel was explicitly disallowed
since it would otherwise tamper with its integrity.

One use case was shown in cf9b1199de ("samples/bpf: Add test/example of
using bpf_probe_write_user bpf helper") where the program DNATs traffic
at the time of connect(2) syscall, meaning, it rewrites the arguments to
a syscall while they're still in userspace, and before the syscall has a
chance to copy the argument into kernel space. These days we have better
mechanisms in BPF for achieving the same (e.g. for load-balancers), but
without having to write to userspace memory.

Of course the bpf_probe_write_user() helper can also be used to abuse
many other things for both good or bad purpose. Outside of BPF, there is
a similar mechanism for ptrace(2) such as PTRACE_PEEK{TEXT,DATA} and
PTRACE_POKE{TEXT,DATA}, but would likely require some more effort.
Commit 96ae522795 explicitly dedicated the helper for experimentation
purpose only. Thus, move the helper's availability behind a newly added
LOCKDOWN_BPF_WRITE_USER lockdown knob so that the helper is disabled under
the "integrity" mode. More fine-grained control can be implemented also
from LSM side with this change.

Fixes: 96ae522795 ("bpf: Add bpf_probe_write_user BPF helper to be called in tracers")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-08-15 14:00:25 +02:00
arch KVM: SVM: Fix off-by-one indexing when nullifying last used SEV VMCB 2021-08-15 14:00:24 +02:00
block blk-iolatency: error out if blk_get_queue() failed in iolatency_set_limit() 2021-08-12 13:22:08 +02:00
certs certs: add 'x509_revocation_list' to gitignore 2021-07-20 16:05:35 +02:00
crypto crypto: sm2 - fix a memory leak in sm2 2021-07-14 16:56:06 +02:00
Documentation Documentation: Fix intiramfs script name 2021-07-28 14:35:47 +02:00
drivers firmware: tee_bnxt: Release TEE shm, session, and context during kexec 2021-08-15 14:00:25 +02:00
fs smb3: rc uninitialized in one fallocate path 2021-08-12 13:22:20 +02:00
include bpf: Add lockdown check for probe_write_user helper 2021-08-15 14:00:25 +02:00
init sched/core: Initialize the idle task with preemption disabled 2021-07-14 16:55:50 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-26 12:06:54 +02:00
kernel bpf: Add lockdown check for probe_write_user helper 2021-08-15 14:00:25 +02:00
lib net: add kcov handle to skb extensions 2021-07-28 14:35:33 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm memblock: make for_each_mem_range() traverse MEMBLOCK_HOTPLUG regions 2021-07-28 14:35:46 +02:00
net net/xfrm/compat: Copy xfrm_spdattr_type_t atributes 2021-08-12 13:22:16 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 16:56:23 +02:00
scripts scripts/tracing: fix the bug that can't parse raw_trace_func 2021-08-12 13:22:12 +02:00
security bpf: Add lockdown check for probe_write_user helper 2021-08-15 14:00:25 +02:00
sound ALSA: usb-audio: Add registration quirk for JBL Quantum 600 2021-08-12 13:22:10 +02:00
tools selftest/bpf: Verifier tests for var-off access 2021-08-08 09:05:24 +02:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: Do not leak memory for duplicate debugfs directories 2021-08-12 13:22:17 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.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 kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
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 f2fs: move ioctl interface definitions to separated file 2021-05-19 10:13:00 +02:00
Makefile Linux 5.10.58 2021-08-12 13:22:21 +02:00
README

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.