io-uring cmd support was added through ee692a21e9 ("fs,io_uring:
add infrastructure for uring-cmd"), this extended the struct
file_operations to allow a new command which each subsystem can use
to enable command passthrough. Add an LSM specific for the command
passthrough which enables LSMs to inspect the command details.
This was discussed long ago without no clear pointer for something
conclusive, so this enables LSMs to at least reject this new file
operation.
[0] https://lkml.kernel.org/r/8adf55db-7bab-f59d-d612-ed906b948d19@schaufler-ca.com
Cc: stable@vger.kernel.org
Fixes: ee692a21e9 ("fs,io_uring: add infrastructure for uring-cmd")
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Pull SafeSetID updates from Micah Morton:
"This contains one commit that touches common kernel code, one that
adds functionality internal to the SafeSetID LSM code, and a few other
commits that only modify the SafeSetID LSM selftest.
The commit that touches common kernel code simply adds an LSM hook in
the setgroups() syscall that mirrors what is done for the existing LSM
hooks in the setuid() and setgid() syscalls. This commit combined with
the SafeSetID-specific one allow the LSM to filter setgroups() calls
according to configured rule sets in the same way that is already done
for setuid() and setgid()"
* tag 'safesetid-6.0' of https://github.com/micah-morton/linux:
LSM: SafeSetID: add setgroups() testing to selftest
LSM: SafeSetID: Add setgroups() security policy handling
security: Add LSM hook to setgroups() syscall
LSM: SafeSetID: add GID testing to selftest
LSM: SafeSetID: selftest cleanup and prepare for GIDs
LSM: SafeSetID: fix userns bug in selftest
Give the LSM framework the ability to filter setgroups() syscalls. There
are already analagous hooks for the set*uid() and set*gid() syscalls.
The SafeSetID LSM will use this new hook to ensure setgroups() calls are
allowed by the installed security policy. Tested by putting print
statement in security_task_fix_setgroups() hook and confirming that it
gets hit when userspace does a setgroups() syscall.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>
Before this change we used to take a shortcut and place the actual
values that would be written to inode->i_{g,u}id into struct iattr. This
had the advantage that we moved idmappings mostly out of the picture
early on but it made reasoning about changes more difficult than it
should be.
The filesystem was never explicitly told that it dealt with an idmapped
mount. The transition to the value that needed to be stored in
inode->i_{g,u}id appeared way too early and increased the probability of
bugs in various codepaths.
We know place the same value in struct iattr no matter if this is an
idmapped mount or not. The vfs will only deal with type safe
vfs{g,u}id_t. This makes it massively safer to perform permission checks
as the type will tell us what checks we need to perform and what helpers
we need to use.
Adapt the security_inode_setattr() helper to pass down the mount's
idmapping to account for that change.
Link: https://lore.kernel.org/r/20220621141454.2914719-8-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Pull Landlock updates from Mickaël Salaün:
- improve the path_rename LSM hook implementations for RENAME_EXCHANGE;
- fix a too-restrictive filesystem control for a rare corner case;
- set the nested sandbox limitation to 16 layers;
- add a new LANDLOCK_ACCESS_FS_REFER access right to properly handle
file reparenting (i.e. full rename and link support);
- add new tests and documentation;
- format code with clang-format to make it easier to maintain and
contribute.
* tag 'landlock-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux: (30 commits)
landlock: Explain how to support Landlock
landlock: Add design choices documentation for filesystem access rights
landlock: Document good practices about filesystem policies
landlock: Document LANDLOCK_ACCESS_FS_REFER and ABI versioning
samples/landlock: Add support for file reparenting
selftests/landlock: Add 11 new test suites dedicated to file reparenting
landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER
LSM: Remove double path_rename hook calls for RENAME_EXCHANGE
landlock: Move filesystem helpers and add a new one
landlock: Fix same-layer rule unions
landlock: Create find_rule() from unmask_layers()
landlock: Reduce the maximum number of layers to 16
landlock: Define access_mask_t to enforce a consistent access mask size
selftests/landlock: Test landlock_create_ruleset(2) argument check ordering
landlock: Change landlock_restrict_self(2) check ordering
landlock: Change landlock_add_rule(2) argument check ordering
selftests/landlock: Add tests for O_PATH
selftests/landlock: Fully test file rename with "remove" access
selftests/landlock: Extend access right tests to directories
selftests/landlock: Add tests for unknown access rights
...
Pull selinux updates from Paul Moore:
"We've got twelve patches queued for v5.19, with most being fairly
minor. The highlights are below:
- The checkreqprot and runtime disable knobs have been deprecated for
some time with no active users that we can find. In an effort to
move things along we are adding a pause when the knobs are used to
help make the deprecation more noticeable in case anyone is still
using these hacks in the shadows.
- We've added the anonymous inode class name to the AVC audit records
when anonymous inodes are involved. This should make writing policy
easier when anonymous inodes are involved.
- More constification work. This is fairly straightforward and the
source of most of the diffstat.
- The usual minor cleanups: remove unnecessary assignments, assorted
style/checkpatch fixes, kdoc fixes, macro while-loop
encapsulations, #include tweaks, etc"
* tag 'selinux-pr-20220523' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
security: declare member holding string literal const
selinux: log anon inode class name
selinux: declare data arrays const
selinux: fix indentation level of mls_ops block
selinux: include necessary headers in headers
selinux: avoid extra semicolon
selinux: update parameter documentation
selinux: resolve checkpatch errors
selinux: don't sleep when CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE is true
selinux: checkreqprot is deprecated, add some ssleep() discomfort
selinux: runtime disable is deprecated, add some ssleep() discomfort
selinux: Remove redundant assignments
KGDB and KDB allow read and write access to kernel memory, and thus
should be restricted during lockdown. An attacker with access to a
serial port (for example, via a hypervisor console, which some cloud
vendors provide over the network) could trigger the debugger so it is
important that the debugger respect the lockdown mode when/if it is
triggered.
Fix this by integrating lockdown into kdb's existing permissions
mechanism. Unfortunately kgdb does not have any permissions mechanism
(although it certainly could be added later) so, for now, kgdb is simply
and brutally disabled by immediately exiting the gdb stub without taking
any action.
For lockdowns established early in the boot (e.g. the normal case) then
this should be fine but on systems where kgdb has set breakpoints before
the lockdown is enacted than "bad things" will happen.
CVE: CVE-2022-21499
Co-developed-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The struct security_hook_list member lsm is assigned in
security_add_hooks() with string literals passed from the individual
security modules. Declare the function parameter and the struct member
const to signal their immutability.
Reported by Clang [-Wwrite-strings]:
security/selinux/hooks.c:7388:63: error: passing 'const char [8]'
to parameter of type 'char *' discards qualifiers
[-Werror,-Wincompatible-pointer-types-discards-qualifiers]
security_add_hooks(selinux_hooks,
ARRAY_SIZE(selinux_hooks), selinux);
^~~~~~~~~
./include/linux/lsm_hooks.h:1629:11: note: passing argument to
parameter 'lsm' here
char *lsm);
^
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Reviewed-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The initialization of "security_hook_heads" is done by casting it to
another structure pointer type, and treating it as an array of "struct
hlist_head" objects. This requires an exception be made in "randstruct",
because otherwise it will emit an error, reducing the effectiveness of
the hardening technique.
Instead of using a cast, initialize the individual struct hlist_head
elements in security_hook_heads explicitly. This removes the need for
the cast and randstruct exception.
Signed-off-by: Bill Wendling <morbo@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220407175930.471870-1-morbo@google.com
Pull selinux updates from Paul Moore:
"We've got a number of SELinux patches queued up, the highlights are:
- Fixup the security_fs_context_parse_param() LSM hook so it executes
all of the LSM hook implementations unless a serious error occurs.
We also correct the SELinux hook implementation so that it returns
zero on success.
- In addition to a few SELinux mount option parsing fixes, we
simplified the parsing by moving it earlier in the process.
The logic was that it was unlikely an admin/user would use the new
mount API and not have the policy loaded before passing the SELinux
options.
- Properly fixed the LSM/SELinux/SCTP hooks with the addition of the
security_sctp_assoc_established() hook.
This work was done in conjunction with the netdev folks and should
complete the move of the SCTP labeling from the endpoints to the
associations.
- Fixed a variety of sparse warnings caused by changes in the "__rcu"
markings of some core kernel structures.
- Ensure we access the superblock's LSM security blob using the
stacking-safe accessors.
- Added the ability for the kernel to always allow FIOCLEX and
FIONCLEX if the "ioctl_skip_cloexec" policy capability is
specified.
- Various constifications improvements, type casting improvements,
additional return value checks, and dead code/parameter removal.
- Documentation fixes"
* tag 'selinux-pr-20220321' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux: (23 commits)
selinux: shorten the policy capability enum names
docs: fix 'make htmldocs' warning in SCTP.rst
selinux: allow FIOCLEX and FIONCLEX with policy capability
selinux: use correct type for context length
selinux: drop return statement at end of void functions
security: implement sctp_assoc_established hook in selinux
security: add sctp_assoc_established hook
selinux: parse contexts for mount options early
selinux: various sparse fixes
selinux: try to use preparsed sid before calling parse_sid()
selinux: Fix selinux_sb_mnt_opts_compat()
LSM: general protection fault in legacy_parse_param
selinux: fix a type cast problem in cred_init_security()
selinux: drop unused macro
selinux: simplify cred_init_security
selinux: do not discard const qualifier in cast
selinux: drop unused parameter of avtab_insert_node
selinux: drop cast to same type
selinux: enclose macro arguments in parenthesis
selinux: declare name parameter of hash_eval const
...
security_sctp_assoc_established() is added to replace
security_inet_conn_established() called in
sctp_sf_do_5_1E_ca(), so that asoc can be accessed in security
subsystem and save the peer secid to asoc->peer_secid.
Fixes: 72e89f5008 ("security: Add support for SCTP security hooks")
Reported-by: Prashanth Prahlad <pprahlad@redhat.com>
Based-on-patch-by: Xin Long <lucien.xin@gmail.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Tested-by: Richard Haines <richard_c_haines@btinternet.com>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Pull security sybsystem fix from James Morris:
"Fix NULL pointer crash in LSM via Ceph, from Vivek Goyal"
* tag 'fixes-v5.17-lsm-ceph-null' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
security, lsm: dentry_init_security() Handle multi LSM registration
A ceph user has reported that ceph is crashing with kernel NULL pointer
dereference. Following is the backtrace.
/proc/version: Linux version 5.16.2-arch1-1 (linux@archlinux) (gcc (GCC)
11.1.0, GNU ld (GNU Binutils) 2.36.1) #1 SMP PREEMPT Thu, 20 Jan 2022
16:18:29 +0000
distro / arch: Arch Linux / x86_64
SELinux is not enabled
ceph cluster version: 16.2.7 (dd0603118f56ab514f133c8d2e3adfc983942503)
relevant dmesg output:
[ 30.947129] BUG: kernel NULL pointer dereference, address:
0000000000000000
[ 30.947206] #PF: supervisor read access in kernel mode
[ 30.947258] #PF: error_code(0x0000) - not-present page
[ 30.947310] PGD 0 P4D 0
[ 30.947342] Oops: 0000 [#1] PREEMPT SMP PTI
[ 30.947388] CPU: 5 PID: 778 Comm: touch Not tainted 5.16.2-arch1-1 #1
86fbf2c313cc37a553d65deb81d98e9dcc2a3659
[ 30.947486] Hardware name: Gigabyte Technology Co., Ltd. B365M
DS3H/B365M DS3H, BIOS F5 08/13/2019
[ 30.947569] RIP: 0010:strlen+0x0/0x20
[ 30.947616] Code: b6 07 38 d0 74 16 48 83 c7 01 84 c0 74 05 48 39 f7 75
ec 31 c0 31 d2 89 d6 89 d7 c3 48 89 f8 31 d2 89 d6 89 d7 c3 0
f 1f 40 00 <80> 3f 00 74 12 48 89 f8 48 83 c0 01 80 38 00 75 f7 48 29 f8 31
ff
[ 30.947782] RSP: 0018:ffffa4ed80ffbbb8 EFLAGS: 00010246
[ 30.947836] RAX: 0000000000000000 RBX: ffffa4ed80ffbc60 RCX:
0000000000000000
[ 30.947904] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
0000000000000000
[ 30.947971] RBP: ffff94b0d15c0ae0 R08: 0000000000000000 R09:
0000000000000000
[ 30.948040] R10: 0000000000000000 R11: 0000000000000000 R12:
0000000000000000
[ 30.948106] R13: 0000000000000001 R14: ffffa4ed80ffbc60 R15:
0000000000000000
[ 30.948174] FS: 00007fc7520f0740(0000) GS:ffff94b7ced40000(0000)
knlGS:0000000000000000
[ 30.948252] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 30.948308] CR2: 0000000000000000 CR3: 0000000104a40001 CR4:
00000000003706e0
[ 30.948376] Call Trace:
[ 30.948404] <TASK>
[ 30.948431] ceph_security_init_secctx+0x7b/0x240 [ceph
49f9c4b9bf5be8760f19f1747e26da33920bce4b]
[ 30.948582] ceph_atomic_open+0x51e/0x8a0 [ceph
49f9c4b9bf5be8760f19f1747e26da33920bce4b]
[ 30.948708] ? get_cached_acl+0x4d/0xa0
[ 30.948759] path_openat+0x60d/0x1030
[ 30.948809] do_filp_open+0xa5/0x150
[ 30.948859] do_sys_openat2+0xc4/0x190
[ 30.948904] __x64_sys_openat+0x53/0xa0
[ 30.948948] do_syscall_64+0x5c/0x90
[ 30.948989] ? exc_page_fault+0x72/0x180
[ 30.949034] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 30.949091] RIP: 0033:0x7fc7521e25bb
[ 30.950849] Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00
00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 0
0 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 54 24 28 64 48 2b 14
25
Core of the problem is that ceph checks for return code from
security_dentry_init_security() and if return code is 0, it assumes
everything is fine and continues to call strlen(name), which crashes.
Typically SELinux LSM returns 0 and sets name to "security.selinux" and
it is not a problem. Or if selinux is not compiled in or disabled, it
returns -EOPNOTSUP and ceph deals with it.
But somehow in this configuration, 0 is being returned and "name" is
not being initialized and that's creating the problem.
Our suspicion is that BPF LSM is registering a hook for
dentry_init_security() and returns hook default of 0.
LSM_HOOK(int, 0, dentry_init_security, struct dentry *dentry,...)
I have not been able to reproduce it just by doing CONFIG_BPF_LSM=y.
Stephen has tested the patch though and confirms it solves the problem
for him.
dentry_init_security() is written in such a way that it expects only one
LSM to register the hook. Atleast that's the expectation with current code.
If another LSM returns a hook and returns default, it will simply return
0 as of now and that will break ceph.
Hence, suggestion is that change semantics of this hook a bit. If there
are no LSMs or no LSM is taking ownership and initializing security context,
then return -EOPNOTSUP. Also allow at max one LSM to initialize security
context. This hook can't deal with multiple LSMs trying to init security
context. This patch implements this new behavior.
Reported-by: Stephen Muth <smuth4@gmail.com>
Tested-by: Stephen Muth <smuth4@gmail.com>
Suggested-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: <stable@vger.kernel.org> # 5.16.0
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: James Morris <jmorris@namei.org>
The usual LSM hook "bail on fail" scheme doesn't work for cases where
a security module may return an error code indicating that it does not
recognize an input. In this particular case Smack sees a mount option
that it recognizes, and returns 0. A call to a BPF hook follows, which
returns -ENOPARAM, which confuses the caller because Smack has processed
its data.
The SELinux hook incorrectly returns 1 on success. There was a time
when this was correct, however the current expectation is that it
return 0 on success. This is repaired.
Reported-by: syzbot+d1e3b1d92d25abf97943@syzkaller.appspotmail.com
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The security_task_getsecid_subj() LSM hook invites misuse by allowing
callers to specify a task even though the hook is only safe when the
current task is referenced. Fix this by removing the task_struct
argument to the hook, requiring LSM implementations to use the
current task. While we are changing the hook declaration we also
rename the function to security_current_getsecid_subj() in an effort
to reinforce that the hook captures the subjective credentials of the
current task and not an arbitrary task on the system.
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This patch reverts two prior patches, e7310c9402
("security: implement sctp_assoc_established hook in selinux") and
7c2ef0240e ("security: add sctp_assoc_established hook"), which
create the security_sctp_assoc_established() LSM hook and provide a
SELinux implementation. Unfortunately these two patches were merged
without proper review (the Reviewed-by and Tested-by tags from
Richard Haines were for previous revisions of these patches that
were significantly different) and there are outstanding objections
from the SELinux maintainers regarding these patches.
Work is currently ongoing to correct the problems identified in the
reverted patches, as well as others that have come up during review,
but it is unclear at this point in time when that work will be ready
for inclusion in the mainline kernel. In the interest of not keeping
objectionable code in the kernel for multiple weeks, and potentially
a kernel release, we are reverting the two problematic patches.
Signed-off-by: Paul Moore <paul@paul-moore.com>
security_sctp_assoc_established() is added to replace
security_inet_conn_established() called in
sctp_sf_do_5_1E_ca(), so that asoc can be accessed in security
subsystem and save the peer secid to asoc->peer_secid.
v1->v2:
- fix the return value of security_sctp_assoc_established() in
security.h, found by kernel test robot and Ondrej.
Fixes: 72e89f5008 ("security: Add support for SCTP security hooks")
Reported-by: Prashanth Prahlad <pprahlad@redhat.com>
Reviewed-by: Richard Haines <richard_c_haines@btinternet.com>
Tested-by: Richard Haines <richard_c_haines@btinternet.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch is to move secid and peer_secid from endpoint to association,
and pass asoc to sctp_assoc_request and sctp_sk_clone instead of ep. As
ep is the local endpoint and asoc represents a connection, and in SCTP
one sk/ep could have multiple asoc/connection, saving secid/peer_secid
for new asoc will overwrite the old asoc's.
Note that since asoc can be passed as NULL, security_sctp_assoc_request()
is moved to the place right after the new_asoc is created in
sctp_sf_do_5_1B_init() and sctp_sf_do_unexpected_init().
v1->v2:
- fix the description of selinux_netlbl_skbuff_setsid(), as Jakub noticed.
- fix the annotation in selinux_sctp_assoc_request(), as Richard Noticed.
Fixes: 72e89f5008 ("security: Add support for SCTP security hooks")
Reported-by: Prashanth Prahlad <pprahlad@redhat.com>
Reviewed-by: Richard Haines <richard_c_haines@btinternet.com>
Tested-by: Richard Haines <richard_c_haines@btinternet.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Right now security_dentry_init_security() only supports single security
label and is used by SELinux only. There are two users of this hook,
namely ceph and nfs.
NFS does not care about xattr name. Ceph hardcodes the xattr name to
security.selinux (XATTR_NAME_SELINUX).
I am making changes to fuse/virtiofs to send security label to virtiofsd
and I need to send xattr name as well. I also hardcoded the name of
xattr to security.selinux.
Stephen Smalley suggested that it probably is a good idea to modify
security_dentry_init_security() to also return name of xattr so that
we can avoid this hardcoding in the callers.
This patch adds a new parameter "const char **xattr_name" to
security_dentry_init_security() and LSM puts the name of xattr
too if caller asked for it (xattr_name != NULL).
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
[PM: fixed typos in the commit description]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Since binder was integrated with selinux, it has passed
'struct task_struct' associated with the binder_proc
to represent the source and target of transactions.
The conversion of task to SID was then done in the hook
implementations. It turns out that there are race conditions
which can result in an incorrect security context being used.
Fix by using the 'struct cred' saved during binder_open and pass
it to the selinux subsystem.
Cc: stable@vger.kernel.org # 5.14 (need backport for earlier stables)
Fixes: 79af73079d ("Add security hooks to binder and implement the hooks for SELinux.")
Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Building with W=1 shows many unused const variable warnings. These can
be silenced, as we're well aware of their being potentially unused:
./include/linux/lsm_hook_defs.h:36:18: error: 'ptrace_access_check_default' defined but not used [-Werror=unused-const-variable=]
36 | LSM_HOOK(int, 0, ptrace_access_check, struct task_struct *child,
| ^~~~~~~~~~~~~~~~~~~
security/security.c:706:32: note: in definition of macro 'LSM_RET_DEFAULT'
706 | #define LSM_RET_DEFAULT(NAME) (NAME##_default)
| ^~~~
security/security.c:711:9: note: in expansion of macro 'DECLARE_LSM_RET_DEFAULT_int'
711 | DECLARE_LSM_RET_DEFAULT_##RET(DEFAULT, NAME)
| ^~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/lsm_hook_defs.h:36:1: note: in expansion of macro 'LSM_HOOK'
36 | LSM_HOOK(int, 0, ptrace_access_check, struct task_struct *child,
| ^~~~~~~~
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: KP Singh <kpsingh@chromium.org>
Cc: linux-security-module@vger.kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/linux-mm/202110131608.zms53FPR-lkp@intel.com/
Fixes: 98e828a065 ("security: Refactor declaration of LSM hooks")
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
A full expalantion of io_uring is beyond the scope of this commit
description, but in summary it is an asynchronous I/O mechanism
which allows for I/O requests and the resulting data to be queued
in memory mapped "rings" which are shared between the kernel and
userspace. Optionally, io_uring offers the ability for applications
to spawn kernel threads to dequeue I/O requests from the ring and
submit the requests in the kernel, helping to minimize the syscall
overhead. Rings are accessed in userspace by memory mapping a file
descriptor provided by the io_uring_setup(2), and can be shared
between applications as one might do with any open file descriptor.
Finally, process credentials can be registered with a given ring
and any process with access to that ring can submit I/O requests
using any of the registered credentials.
While the io_uring functionality is widely recognized as offering a
vastly improved, and high performing asynchronous I/O mechanism, its
ability to allow processes to submit I/O requests with credentials
other than its own presents a challenge to LSMs. When a process
creates a new io_uring ring the ring's credentials are inhertied
from the calling process; if this ring is shared with another
process operating with different credentials there is the potential
to bypass the LSMs security policy. Similarly, registering
credentials with a given ring allows any process with access to that
ring to submit I/O requests with those credentials.
In an effort to allow LSMs to apply security policy to io_uring I/O
operations, this patch adds two new LSM hooks. These hooks, in
conjunction with the LSM anonymous inode support previously
submitted, allow an LSM to apply access control policy to the
sharing of io_uring rings as well as any io_uring credential changes
requested by a process.
The new LSM hooks are described below:
* int security_uring_override_creds(cred)
Controls if the current task, executing an io_uring operation,
is allowed to override it's credentials with @cred. In cases
where the current task is a user application, the current
credentials will be those of the user application. In cases
where the current task is a kernel thread servicing io_uring
requests the current credentials will be those of the io_uring
ring (inherited from the process that created the ring).
* int security_uring_sqpoll(void)
Controls if the current task is allowed to create an io_uring
polling thread (IORING_SETUP_SQPOLL). Without a SQPOLL thread
in the kernel processes must submit I/O requests via
io_uring_enter(2) which allows us to compare any requested
credential changes against the application making the request.
With a SQPOLL thread, we can no longer compare requested
credential changes against the application making the request,
the comparison is made against the ring's credentials.
Signed-off-by: Paul Moore <paul@paul-moore.com>
