Pull bpf 'struct fd' updates from Alexei Starovoitov:
"This includes struct_fd BPF changes from Al and Andrii"
* tag 'bpf-next-6.12-struct-fd' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next:
bpf: convert bpf_token_create() to CLASS(fd, ...)
security,bpf: constify struct path in bpf_token_create() LSM hook
bpf: more trivial fdget() conversions
bpf: trivial conversions for fdget()
bpf: switch maps to CLASS(fd, ...)
bpf: factor out fetching bpf_map from FD and adding it to used_maps list
bpf: switch fdget_raw() uses to CLASS(fd_raw, ...)
bpf: convert __bpf_prog_get() to CLASS(fd, ...)
There is no reason why struct path pointer shouldn't be const-qualified
when being passed into bpf_token_create() LSM hook. Add that const.
Acked-by: Paul Moore <paul@paul-moore.com> (LSM/SELinux)
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Because these are equals to MAX_LSM_COUNT. Also, we can avoid dynamic
memory allocation for ordered_lsms because MAX_LSM_COUNT is a constant.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Paul Moore <paul@paul-moore.com>
LSM hooks are currently invoked from a linked list as indirect calls
which are invoked using retpolines as a mitigation for speculative
attacks (Branch History / Target injection) and add extra overhead which
is especially bad in kernel hot paths:
security_file_ioctl:
0xff...0320 <+0>: endbr64
0xff...0324 <+4>: push %rbp
0xff...0325 <+5>: push %r15
0xff...0327 <+7>: push %r14
0xff...0329 <+9>: push %rbx
0xff...032a <+10>: mov %rdx,%rbx
0xff...032d <+13>: mov %esi,%ebp
0xff...032f <+15>: mov %rdi,%r14
0xff...0332 <+18>: mov $0xff...7030,%r15
0xff...0339 <+25>: mov (%r15),%r15
0xff...033c <+28>: test %r15,%r15
0xff...033f <+31>: je 0xff...0358 <security_file_ioctl+56>
0xff...0341 <+33>: mov 0x18(%r15),%r11
0xff...0345 <+37>: mov %r14,%rdi
0xff...0348 <+40>: mov %ebp,%esi
0xff...034a <+42>: mov %rbx,%rdx
0xff...034d <+45>: call 0xff...2e0 <__x86_indirect_thunk_array+352>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Indirect calls that use retpolines leading to overhead, not just due
to extra instruction but also branch misses.
0xff...0352 <+50>: test %eax,%eax
0xff...0354 <+52>: je 0xff...0339 <security_file_ioctl+25>
0xff...0356 <+54>: jmp 0xff...035a <security_file_ioctl+58>
0xff...0358 <+56>: xor %eax,%eax
0xff...035a <+58>: pop %rbx
0xff...035b <+59>: pop %r14
0xff...035d <+61>: pop %r15
0xff...035f <+63>: pop %rbp
0xff...0360 <+64>: jmp 0xff...47c4 <__x86_return_thunk>
The indirect calls are not really needed as one knows the addresses of
enabled LSM callbacks at boot time and only the order can possibly
change at boot time with the lsm= kernel command line parameter.
An array of static calls is defined per LSM hook and the static calls
are updated at boot time once the order has been determined.
With the hook now exposed as a static call, one can see that the
retpolines are no longer there and the LSM callbacks are invoked
directly:
security_file_ioctl:
0xff...0ca0 <+0>: endbr64
0xff...0ca4 <+4>: nopl 0x0(%rax,%rax,1)
0xff...0ca9 <+9>: push %rbp
0xff...0caa <+10>: push %r14
0xff...0cac <+12>: push %rbx
0xff...0cad <+13>: mov %rdx,%rbx
0xff...0cb0 <+16>: mov %esi,%ebp
0xff...0cb2 <+18>: mov %rdi,%r14
0xff...0cb5 <+21>: jmp 0xff...0cc7 <security_file_ioctl+39>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Static key enabled for SELinux
0xffffffff818f0cb7 <+23>: jmp 0xff...0cde <security_file_ioctl+62>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Static key enabled for BPF LSM. This is something that is changed to
default to false to avoid the existing side effect issues of BPF LSM
[1] in a subsequent patch.
0xff...0cb9 <+25>: xor %eax,%eax
0xff...0cbb <+27>: xchg %ax,%ax
0xff...0cbd <+29>: pop %rbx
0xff...0cbe <+30>: pop %r14
0xff...0cc0 <+32>: pop %rbp
0xff...0cc1 <+33>: cs jmp 0xff...0000 <__x86_return_thunk>
0xff...0cc7 <+39>: endbr64
0xff...0ccb <+43>: mov %r14,%rdi
0xff...0cce <+46>: mov %ebp,%esi
0xff...0cd0 <+48>: mov %rbx,%rdx
0xff...0cd3 <+51>: call 0xff...3230 <selinux_file_ioctl>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Direct call to SELinux.
0xff...0cd8 <+56>: test %eax,%eax
0xff...0cda <+58>: jne 0xff...0cbd <security_file_ioctl+29>
0xff...0cdc <+60>: jmp 0xff...0cb7 <security_file_ioctl+23>
0xff...0cde <+62>: endbr64
0xff...0ce2 <+66>: mov %r14,%rdi
0xff...0ce5 <+69>: mov %ebp,%esi
0xff...0ce7 <+71>: mov %rbx,%rdx
0xff...0cea <+74>: call 0xff...e220 <bpf_lsm_file_ioctl>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Direct call to BPF LSM.
0xff...0cef <+79>: test %eax,%eax
0xff...0cf1 <+81>: jne 0xff...0cbd <security_file_ioctl+29>
0xff...0cf3 <+83>: jmp 0xff...0cb9 <security_file_ioctl+25>
0xff...0cf5 <+85>: endbr64
0xff...0cf9 <+89>: mov %r14,%rdi
0xff...0cfc <+92>: mov %ebp,%esi
0xff...0cfe <+94>: mov %rbx,%rdx
0xff...0d01 <+97>: pop %rbx
0xff...0d02 <+98>: pop %r14
0xff...0d04 <+100>: pop %rbp
0xff...0d05 <+101>: ret
0xff...0d06 <+102>: int3
0xff...0d07 <+103>: int3
0xff...0d08 <+104>: int3
0xff...0d09 <+105>: int3
While this patch uses static_branch_unlikely indicating that an LSM hook
is likely to be not present. In most cases this is still a better choice
as even when an LSM with one hook is added, empty slots are created for
all LSM hooks (especially when many LSMs that do not initialize most
hooks are present on the system).
There are some hooks that don't use the call_int_hook or
call_void_hook. These hooks are updated to use a new macro called
lsm_for_each_hook where the lsm_callback is directly invoked as an
indirect call.
Below are results of the relevant Unixbench system benchmarks with BPF LSM
and SELinux enabled with default policies enabled with and without these
patches.
Benchmark Delta(%): (+ is better)
==========================================================================
Execl Throughput +1.9356
File Write 1024 bufsize 2000 maxblocks +6.5953
Pipe Throughput +9.5499
Pipe-based Context Switching +3.0209
Process Creation +2.3246
Shell Scripts (1 concurrent) +1.4975
System Call Overhead +2.7815
System Benchmarks Index Score (Partial Only): +3.4859
In the best case, some syscalls like eventfd_create benefitted to about
~10%.
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This patch introduces a new hook to save inode's integrity
data. For example, for fsverity enabled files, LSMs can use this hook to
save the existence of verified fsverity builtin signature into the inode's
security blob, and LSMs can make access decisions based on this data.
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
[PM: subject line tweak, removed changelog]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Allows author of IPE policy to indicate trust for a singular dm-verity
volume, identified by roothash, through "dmverity_roothash" and all
signed and validated dm-verity volumes, through "dmverity_signature".
Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
[PM: fixed some line length issues in the comments]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This patch introduces a new LSM blob to the block_device structure,
enabling the security subsystem to store security-sensitive data related
to block devices. Currently, for a device mapper's mapped device containing
a dm-verity target, critical security information such as the roothash and
its signing state are not readily accessible. Specifically, while the
dm-verity volume creation process passes the dm-verity roothash and its
signature from userspace to the kernel, the roothash is stored privately
within the dm-verity target, and its signature is discarded
post-verification. This makes it extremely hard for the security subsystem
to utilize these data.
With the addition of the LSM blob to the block_device structure, the
security subsystem can now retain and manage important security metadata
such as the roothash and the signing state of a dm-verity by storing them
inside the blob. Access decisions can then be based on these stored data.
The implementation follows the same approach used for security blobs in
other structures like struct file, struct inode, and struct superblock.
The initialization of the security blob occurs after the creation of the
struct block_device, performed by the security subsystem. Similarly, the
security blob is freed by the security subsystem before the struct
block_device is deallocated or freed.
This patch also introduces a new hook security_bdev_setintegrity() to save
block device's integrity data to the new LSM blob. For example, for
dm-verity, it can use this hook to expose its roothash and signing state
to LSMs, then LSMs can save these data into the LSM blob.
Please note that the new hook should be invoked every time the security
information is updated to keep these data current. For example, in
dm-verity, if the mapping table is reloaded and configured to use a
different dm-verity target with a new roothash and signing information,
the previously stored data in the LSM blob will become obsolete. It is
crucial to re-invoke the hook to refresh these data and ensure they are up
to date. This necessity arises from the design of device-mapper, where a
device-mapper device is first created, and then targets are subsequently
loaded into it. These targets can be modified multiple times during the
device's lifetime. Therefore, while the LSM blob is allocated during the
creation of the block device, its actual contents are not initialized at
this stage and can change substantially over time. This includes
alterations from data that the LSM 'trusts' to those it does not, making
it essential to handle these changes correctly. Failure to address this
dynamic aspect could potentially allow for bypassing LSM checks.
Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
[PM: merge fuzz, subject line tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This patch introduces a new hook to notify security system that the
content of initramfs has been unpacked into the rootfs.
Upon receiving this notification, the security system can activate
a policy to allow only files that originated from the initramfs to
execute or load into kernel during the early stages of booting.
This approach is crucial for minimizing the attack surface by
ensuring that only trusted files from the initramfs are operational
in the critical boot phase.
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
[PM: subject line tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Integrity Policy Enforcement (IPE) is an LSM that provides an
complimentary approach to Mandatory Access Control than existing LSMs
today.
Existing LSMs have centered around the concept of access to a resource
should be controlled by the current user's credentials. IPE's approach,
is that access to a resource should be controlled by the system's trust
of a current resource.
The basis of this approach is defining a global policy to specify which
resource can be trusted.
Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
[PM: subject line tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>
The LSM framework has an existing inode_free_security() hook which
is used by LSMs that manage state associated with an inode, but
due to the use of RCU to protect the inode, special care must be
taken to ensure that the LSMs do not fully release the inode state
until it is safe from a RCU perspective.
This patch implements a new inode_free_security_rcu() implementation
hook which is called when it is safe to free the LSM's internal inode
state. Unfortunately, this new hook does not have access to the inode
itself as it may already be released, so the existing
inode_free_security() hook is retained for those LSMs which require
access to the inode.
Cc: stable@vger.kernel.org
Reported-by: syzbot+5446fbf332b0602ede0b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/00000000000076ba3b0617f65cc8@google.com
Signed-off-by: Paul Moore <paul@paul-moore.com>
Some cleanup and style corrections for lsm_hooks.h.
* Drop the lsm_inode_alloc() extern declaration, it is not needed.
* Relocate lsm_get_xattr_slot() and extern variables in the file to
improve grouping of related objects.
* Don't use tabs to needlessly align structure fields.
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
To be consistent with most LSM hooks, convert the return value of
hook inode_copy_up_xattr to 0 or a negative error code.
Before:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, 1 when
discarding xattr, -EOPNOTSUPP if it does not know xattr, or any
other negative error code otherwise.
After:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, *-ECANCELED*
when discarding xattr, -EOPNOTSUPP if it does not know xattr, or
any other negative error code otherwise.
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
To be consistent with most LSM hooks, convert the return value of
hook vm_enough_memory to 0 or a negative error code.
Before:
- Hook vm_enough_memory returns 1 if permission is granted, 0 if not.
- LSM_RET_DEFAULT(vm_enough_memory_mm) is 1.
After:
- Hook vm_enough_memory reutrns 0 if permission is granted, negative
error code if not.
- LSM_RET_DEFAULT(vm_enough_memory_mm) is 0.
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.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>
Create a helper function lsm_blob_alloc() for general use in the hook
specific functions that allocate LSM blobs. Change the hook specific
functions to use this helper. This reduces the code size by a small
amount and will make adding new instances of infrastructure managed
security blobs easier.
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 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>
Pull lsm updates from Paul Moore:
"Two LSM patches focused on cleaning up the inode xattr capability
handling"
* tag 'lsm-pr-20240715' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm:
selinux,smack: remove the capability checks in the removexattr hooks
lsm: fixup the inode xattr capability handling
The current security_inode_setxattr() and security_inode_removexattr()
hooks rely on individual LSMs to either call into the associated
capability hooks (cap_inode_setxattr() or cap_inode_removexattr()), or
return a magic value of 1 to indicate that the LSM layer itself should
perform the capability checks. Unfortunately, with the default return
value for these LSM hooks being 0, an individual LSM hook returning a
1 will cause the LSM hook processing to exit early, potentially
skipping a LSM. Thankfully, with the exception of the BPF LSM, none
of the LSMs which currently register inode xattr hooks should end up
returning a value of 1, and in the BPF LSM case, with the BPF LSM hooks
executing last there should be no real harm in stopping processing of
the LSM hooks. However, the reliance on the individual LSMs to either
call the capability hooks themselves, or signal the LSM with a return
value of 1, is fragile and relies on a specific set of LSMs being
enabled. This patch is an effort to resolve, or minimize, these
issues.
Before we discuss the solution, there are a few observations and
considerations that we need to take into account:
* BPF LSM registers an implementation for every LSM hook, and that
implementation simply returns the hook's default return value, a
0 in this case. We want to ensure that the default BPF LSM behavior
results in the capability checks being called.
* SELinux and Smack do not expect the traditional capability checks
to be applied to the xattrs that they "own".
* SELinux and Smack are currently written in such a way that the
xattr capability checks happen before any additional LSM specific
access control checks. SELinux does apply SELinux specific access
controls to all xattrs, even those not "owned" by SELinux.
* IMA and EVM also register xattr hooks but assume that the LSM layer
and specific LSMs have already authorized the basic xattr operation.
In order to ensure we perform the capability based access controls
before the individual LSM access controls, perform only one capability
access control check for each operation, and clarify the logic around
applying the capability controls, we need a mechanism to determine if
any of the enabled LSMs "own" a particular xattr and want to take
responsibility for controlling access to that xattr. The solution in
this patch is to create a new LSM hook, 'inode_xattr_skipcap', that is
not exported to the rest of the kernel via a security_XXX() function,
but is used by the LSM layer to determine if a LSM wants to control
access to a given xattr and avoid the traditional capability controls.
Registering an inode_xattr_skipcap hook is optional, if a LSM declines
to register an implementation, or uses an implementation that simply
returns the default value (0), there is no effect as the LSM continues
to enforce the capability based controls (unless another LSM takes
ownership of the xattr). If none of the LSMs signal that the
capability checks should be skipped, the capability check is performed
and if access is granted the individual LSM xattr access control hooks
are executed, keeping with the DAC-before-LSM convention.
Cc: stable@vger.kernel.org
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Copying up xattrs is solely based on the security xattr name. For finer
granularity add a dentry parameter to the security_inode_copy_up_xattr
hook definition, allowing decisions to be based on the xattr content as
well.
Co-developed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Paul Moore <paul@paul-moore.com> (LSM,SELinux)
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Commit 08abce60d6 ("security: Introduce path_post_mknod hook")
introduced security_path_post_mknod(), to replace the IMA-specific call
to ima_post_path_mknod().
For symmetry with security_path_mknod(), security_path_post_mknod() was
called after a successful mknod operation, for any file type, rather
than only for regular files at the time there was the IMA call.
However, as reported by VFS maintainers, successful mknod operation does
not mean that the dentry always has an inode attached to it (for
example, not for FIFOs on a SAMBA mount).
If that condition happens, the kernel crashes when
security_path_post_mknod() attempts to verify if the inode associated to
the dentry is private.
Move security_path_post_mknod() where the ima_post_path_mknod() call was,
which is obviously correct from IMA/EVM perspective. IMA/EVM are the only
in-kernel users, and only need to inspect regular files.
Reported-by: Steve French <smfrench@gmail.com>
Closes: https://lore.kernel.org/linux-kernel/CAH2r5msAVzxCUHHG8VKrMPUKQHmBpE6K9_vjhgDa1uAvwx4ppw@mail.gmail.com/
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 08abce60d6 ("security: Introduce path_post_mknod hook")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
