linux-stable/security
Daniel Borkmann 51e1bb9eea bpf: Add lockdown check for probe_write_user helper
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>
2021-08-10 10:10:10 +02:00
..
apparmor apparmor: use get_unaligned() only for multi-byte words 2021-05-17 13:30:29 +02:00
bpf bpf: Implement task local storage 2020-11-06 08:08:37 -08:00
integrity evm: Check xattr size discrepancy between kernel and user 2021-06-21 08:34:21 -04:00
keys trusted-keys: match tpm_get_ops on all return paths 2021-05-12 22:36:37 +03:00
landlock landlock: Enable user space to infer supported features 2021-04-22 12:22:11 -07:00
loadpin LSM: Add "contents" flag to kernel_read_file hook 2020-10-05 13:37:03 +02:00
lockdown Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2020-06-02 17:36:24 -07:00
safesetid LSM: SafeSetID: Mark safesetid_initialized as __initdata 2021-06-10 09:52:32 -07:00
selinux selinux: correct the return value when loads initial sids 2021-08-02 09:59:50 -04:00
smack Smack: fix doc warning 2021-06-08 10:23:08 -07:00
tomoyo tomoyo: fix doc warnings 2021-06-16 00:01:28 +09:00
yama task_work: cleanup notification modes 2020-10-17 15:05:30 -06:00
commoncap.c Miscellaneous minor fixes for v5.13. 2021-04-27 19:32:55 -07:00
device_cgroup.c device_cgroup: Fix RCU list debugging warning 2020-08-20 11:25:03 -07:00
inode.c
Kconfig landlock: Set up the security framework and manage credentials 2021-04-22 12:22:10 -07:00
Kconfig.hardening kasan: remove redundant config option 2021-04-16 16:10:36 -07:00
lsm_audit.c audit: remove unnecessary 'ret' initialization 2021-06-11 13:21:28 -04:00
Makefile landlock: Add object management 2021-04-22 12:22:10 -07:00
min_addr.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
security.c bpf: Add lockdown check for probe_write_user helper 2021-08-10 10:10:10 +02:00