The per-task avdcache was incorrectly saving and reusing the
audited vector computed by avc_audit_required() rather than
recomputing based on the currently requested permissions and
distinguishing the denied versus allowed cases. As a result,
some permission checks were not being audited, e.g.
directory write checks after a previously cached directory
search check.
Cc: stable@vger.kernel.org
Fixes: dde3a5d0f4 ("selinux: move avdcache to per-task security struct")
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
[PM: line wrap tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>
The existing SELinux security model for overlayfs is to allow access if
the current task is able to access the top level file (the "user" file)
and the mounter's credentials are sufficient to access the lower
level file (the "backing" file). Unfortunately, the current code does
not properly enforce these access controls for both mmap() and mprotect()
operations on overlayfs filesystems.
This patch makes use of the newly created security_mmap_backing_file()
LSM hook to provide the missing backing file enforcement for mmap()
operations, and leverages the backing file API and new LSM blob to
provide the necessary information to properly enforce the mprotect()
access controls.
Cc: stable@vger.kernel.org
Acked-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
BPF token support was introduced to allow a privileged process to delegate
limited BPF functionality—such as map creation and program loading—to
an unprivileged process:
https://lore.kernel.org/linux-security-module/20231130185229.2688956-1-andrii@kernel.org/
This patch adds SELinux support for controlling BPF token access. With
this change, SELinux policies can now enforce constraints on BPF token
usage based on both the delegating (privileged) process and the recipient
(unprivileged) process.
Supported operations currently include:
- map_create
- prog_load
High-level workflow:
1. An unprivileged process creates a VFS context via `fsopen()` and
obtains a file descriptor.
2. This descriptor is passed to a privileged process, which configures
BPF token delegation options and mounts a BPF filesystem.
3. SELinux records the `creator_sid` of the privileged process during
mount setup.
4. The unprivileged process then uses this BPF fs mount to create a
token and attach it to subsequent BPF syscalls.
5. During verification of `map_create` and `prog_load`, SELinux uses
`creator_sid` and the current SID to check policy permissions via:
avc_has_perm(creator_sid, current_sid, SECCLASS_BPF,
BPF__MAP_CREATE, NULL);
The implementation introduces two new permissions:
- map_create_as
- prog_load_as
At token creation time, SELinux verifies that the current process has the
appropriate `*_as` permission (depending on the `allowed_cmds` value in
the bpf_token) to act on behalf of the `creator_sid`.
Example SELinux policy:
allow test_bpf_t self:bpf {
map_create map_read map_write prog_load prog_run
map_create_as prog_load_as
};
Additionally, a new policy capability bpf_token_perms is added to ensure
backward compatibility. If disabled, previous behavior ((checks based on
current process SID)) is preserved.
Signed-off-by: Eric Suen <ericsu@linux.microsoft.com>
Tested-by: Daniel Durning <danieldurning.work@gmail.com>
Reviewed-by: Daniel Durning <danieldurning.work@gmail.com>
[PM: merge fuzz, subject tweaks, whitespace tweaks, line length tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Along with the renaming from task_security_struct to cred_security_struct,
rename the local variables to "crsec" from "tsec". This both fits with
existing conventions and helps distinguish between task and cred related
variables.
No functional changes.
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The avdcache is meant to be per-task; move it to a new
task_security_struct that is duplicated per-task.
Cc: stable@vger.kernel.org
Fixes: 5d7ddc59b3 ("selinux: reduce path walk overhead")
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
[PM: line length fixes]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Before Linux had cred structures, the SELinux task_security_struct was
per-task and although the structure was switched to being per-cred
long ago, the name was never updated. This change renames it to
cred_security_struct to avoid confusion and pave the way for the
introduction of an actual per-task security structure for SELinux. No
functional change.
Cc: stable@vger.kernel.org
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This patch introduces LSM blob support for BPF maps, programs, and
tokens to enable LSM stacking and multiplexing of LSM modules that
govern BPF objects. Additionally, the existing BPF hooks used by
SELinux have been updated to utilize the new blob infrastructure,
removing the assumption of exclusive ownership of the security
pointer.
Signed-off-by: Blaise Boscaccy <bboscaccy@linux.microsoft.com>
[PM: dropped local variable init, style fixes]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Extend the task avdcache to also cache whether the task SID is both
permissive and neveraudit, and return immediately if so in both
selinux_inode_getattr() and selinux_inode_permission().
The same approach could be applied to many of the hook functions
although the avdcache would need to be updated for more than directory
search checks in order for this optimization to be beneficial for checks
on objects other than directories.
To test, apply https://github.com/SELinuxProject/selinux/pull/473 to
your selinux userspace, build and install libsepol, and use the following
CIL policy module:
$ cat neverauditpermissive.cil
(typeneveraudit unconfined_t)
(typepermissive unconfined_t)
Without this module inserted, running the following commands:
perf record make -jN # on an already built allmodconfig tree
perf report --sort=symbol,dso
yields the following percentages (only showing __d_lookup_rcu for
reference and only showing relevant SELinux functions):
1.65% [k] __d_lookup_rcu
0.53% [k] selinux_inode_permission
0.40% [k] selinux_inode_getattr
0.15% [k] avc_lookup
0.05% [k] avc_has_perm
0.05% [k] avc_has_perm_noaudit
0.02% [k] avc_policy_seqno
0.02% [k] selinux_file_permission
0.01% [k] selinux_inode_alloc_security
0.01% [k] selinux_file_alloc_security
for a total of 1.24% for SELinux compared to 1.65% for
__d_lookup_rcu().
After running the following command to insert this module:
semodule -i neverauditpermissive.cil
and then re-running the same perf commands from above yields
the following non-zero percentages:
1.74% [k] __d_lookup_rcu
0.31% [k] selinux_inode_permission
0.03% [k] selinux_inode_getattr
0.03% [k] avc_policy_seqno
0.01% [k] avc_lookup
0.01% [k] selinux_file_permission
0.01% [k] selinux_file_open
for a total of 0.40% for SELinux compared to 1.74% for
__d_lookup_rcu().
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Reduce the SELinux performance overhead during path walks through the
use of a per-task directory access cache and some minor code
optimizations. The directory access cache is per-task because it allows
for a lockless cache while also fitting well with a common application
pattern of heavily accessing a relatively small number of SELinux
directory labels. The cache is inherited by child processes when the
child runs with the same SELinux domain as the parent, and invalidated
on changes to the task's SELinux domain or the loaded SELinux policy.
A cache of four entries was chosen based on testing with the Fedora
"targeted" policy, a SELinux Reference Policy variant, and
'make allmodconfig' on Linux v6.14.
Code optimizations include better use of inline functions to reduce
function calls in the common case, especially in the inode revalidation
code paths, and elimination of redundant checks between the LSM and
SELinux layers.
As mentioned briefly above, aside from general use and regression
testing with the selinux-testsuite, performance was measured using
'make allmodconfig' with Linux v6.14 as a base reference. As expected,
there were variations from one test run to another, but the measurements
below are a good representation of the test results seen on my test
system.
* Linux v6.14
REF
1.26% [k] __d_lookup_rcu
SELINUX (1.31%)
0.58% [k] selinux_inode_permission
0.29% [k] avc_lookup
0.25% [k] avc_has_perm_noaudit
0.19% [k] __inode_security_revalidate
* Linux v6.14 + patch
REF
1.41% [k] __d_lookup_rcu
SELINUX (0.89%)
0.65% [k] selinux_inode_permission
0.15% [k] avc_lookup
0.05% [k] avc_has_perm_noaudit
0.04% [k] avc_policy_seqno
X.XX% [k] __inode_security_revalidate (now inline)
In both cases the __d_lookup_rcu() function was used as a reference
point to establish a context for the SELinux related functions. On a
unpatched Linux v6.14 system we see the time spent in the combined
SELinux functions exceeded that of __d_lookup_rcu(), 1.31% compared to
1.26%. However, with this patch applied the time spent in the combined
SELinux functions dropped to roughly 65% of the time spent in
__d_lookup_rcu(), 0.89% compared to 1.41%. Aside from the significant
decrease in time spent in the SELinux AVC, it appears that any additional
time spent searching and updating the cache is offset by other code
improvements, e.g. time spent in selinux_inode_permission() +
__inode_security_revalidate() + avc_policy_seqno() is less on the
patched kernel than the unpatched kernel.
It is worth noting that in this patch the use of the per-task cache is
limited to the security_inode_permission() LSM callback,
selinux_inode_permission(), but future work could expand the cache into
inode_has_perm(), likely through consolidation of the two functions.
While this would likely have little to no impact on path walks, it
may benefit other operations.
Reviewed-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Tested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Move management of the perf_event->security blob out of the individual
security modules and into the security infrastructure. Instead of
allocating the blobs from within the modules the modules tell the
infrastructure how much space is required, and the space is allocated
there. There are no longer any modules that require the perf_event_free()
hook. The hook definition has been removed.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
[PM: subject tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Move management of the infiniband security blob out of the individual
security modules and into the LSM infrastructure. The security modules
tell the infrastructure how much space they require at initialization.
There are no longer any modules that require the ib_free() hook.
The hook definition has been removed.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
[PM: subject tweak, selinux style fixes]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Move management of the dev_tun security blob out of the individual
security modules and into the LSM infrastructure. The security modules
tell the infrastructure how much space they require at initialization.
There are no longer any modules that require the dev_tun_free hook.
The hook definition has been removed.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
[PM: subject tweak, selinux style fixes]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Move management of the key->security blob out of the individual security
modules and into the security infrastructure. Instead of allocating the
blobs from within the modules the modules tell the infrastructure how
much space is required, and the space is allocated there. There are
no existing modules that require a key_free hook, so the call to it and
the definition for it have been removed.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
[PM: subject tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Move management of the sock->sk_security blob out
of the individual security modules and into the security
infrastructure. Instead of allocating the blobs from within
the modules the modules tell the infrastructure how much
space is required, and the space is allocated there.
Acked-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: subject tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>
As part of on ongoing effort to perform more automated testing and
provide more tools for individual developers to validate their
patches before submitting, we are trying to make our code
"clang-format clean". My hope is that once we have fixed all of our
style "quirks", developers will be able to run clang-format on their
patches to help avoid silly formatting problems and ensure their
changes fit in well with the rest of the SELinux kernel code.
Signed-off-by: Paul Moore <paul@paul-moore.com>
Change "NSA SELinux" to just "SELinux" in Kconfig help text and
comments. While NSA was the original primary developer and continues to
help maintain SELinux, SELinux has long since transitioned to a wide
community of developers and maintainers. SELinux has been part of the
mainline Linux kernel for nearly 20 years now [1] and has received
contributions from many individuals and organizations.
[1] https://lore.kernel.org/lkml/Pine.LNX.4.44.0308082228470.1852-100000@home.osdl.org/
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
It appears to have been needed for selinux_complete_init() in the past,
but today it's useless.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Randomize the layout of key selinux data structures.
Initially this is applied to the selinux_state, selinux_ss,
policydb, and task_security_struct data structures.
NB To test/use this mechanism, one must install the
necessary build-time dependencies, e.g. gcc-plugin-devel on Fedora,
and enable CONFIG_GCC_PLUGIN_RANDSTRUCT in the kernel configuration.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Kees Cook <keescook@chromium.org>
[PM: double semi-colon fixed]
Signed-off-by: Paul Moore <paul@paul-moore.com>
In current mainline, the degree of access to perf_event_open(2) system
call depends on the perf_event_paranoid sysctl. This has a number of
limitations:
1. The sysctl is only a single value. Many types of accesses are controlled
based on the single value thus making the control very limited and
coarse grained.
2. The sysctl is global, so if the sysctl is changed, then that means
all processes get access to perf_event_open(2) opening the door to
security issues.
This patch adds LSM and SELinux access checking which will be used in
Android to access perf_event_open(2) for the purposes of attaching BPF
programs to tracepoints, perf profiling and other operations from
userspace. These operations are intended for production systems.
5 new LSM hooks are added:
1. perf_event_open: This controls access during the perf_event_open(2)
syscall itself. The hook is called from all the places that the
perf_event_paranoid sysctl is checked to keep it consistent with the
systctl. The hook gets passed a 'type' argument which controls CPU,
kernel and tracepoint accesses (in this context, CPU, kernel and
tracepoint have the same semantics as the perf_event_paranoid sysctl).
Additionally, I added an 'open' type which is similar to
perf_event_paranoid sysctl == 3 patch carried in Android and several other
distros but was rejected in mainline [1] in 2016.
2. perf_event_alloc: This allocates a new security object for the event
which stores the current SID within the event. It will be useful when
the perf event's FD is passed through IPC to another process which may
try to read the FD. Appropriate security checks will limit access.
3. perf_event_free: Called when the event is closed.
4. perf_event_read: Called from the read(2) and mmap(2) syscalls for the event.
5. perf_event_write: Called from the ioctl(2) syscalls for the event.
[1] https://lwn.net/Articles/696240/
Since Peter had suggest LSM hooks in 2016 [1], I am adding his
Suggested-by tag below.
To use this patch, we set the perf_event_paranoid sysctl to -1 and then
apply selinux checking as appropriate (default deny everything, and then
add policy rules to give access to domains that need it). In the future
we can remove the perf_event_paranoid sysctl altogether.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Co-developed-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: James Morris <jmorris@namei.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: rostedt@goodmis.org
Cc: Yonghong Song <yhs@fb.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: jeffv@google.com
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: primiano@google.com
Cc: Song Liu <songliubraving@fb.com>
Cc: rsavitski@google.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Matthew Garrett <matthewgarrett@google.com>
Link: https://lkml.kernel.org/r/20191014170308.70668-1-joel@joelfernandes.org
Pull selinux updates from Paul Moore:
- Add LSM hooks, and SELinux access control hooks, for dnotify,
fanotify, and inotify watches. This has been discussed with both the
LSM and fs/notify folks and everybody is good with these new hooks.
- The LSM stacking changes missed a few calls to current_security() in
the SELinux code; we fix those and remove current_security() for
good.
- Improve our network object labeling cache so that we always return
the object's label, even when under memory pressure. Previously we
would return an error if we couldn't allocate a new cache entry, now
we always return the label even if we can't create a new cache entry
for it.
- Convert the sidtab atomic_t counter to a normal u32 with
READ/WRITE_ONCE() and memory barrier protection.
- A few patches to policydb.c to clean things up (remove forward
declarations, long lines, bad variable names, etc)
* tag 'selinux-pr-20190917' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
lsm: remove current_security()
selinux: fix residual uses of current_security() for the SELinux blob
selinux: avoid atomic_t usage in sidtab
fanotify, inotify, dnotify, security: add security hook for fs notifications
selinux: always return a secid from the network caches if we find one
selinux: policydb - rename type_val_to_struct_array
selinux: policydb - fix some checkpatch.pl warnings
selinux: shuffle around policydb.c to get rid of forward declarations
We need to use selinux_cred() to fetch the SELinux cred blob instead
of directly using current->security or current_security(). There
were a couple of lingering uses of current_security() in the SELinux code
that were apparently missed during the earlier conversions. IIUC, this
would only manifest as a bug if multiple security modules including
SELinux are enabled and SELinux is not first in the lsm order. After
this change, there appear to be no other users of current_security()
in-tree; perhaps we should remove it altogether.
Fixes: bbd3662a83 ("Infrastructure management of the cred security blob")
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Based on 2 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
