We have an upper bound on "maplevel" but forgot to check for negative
values.
Fixes: e114e47377 ("Smack: Simplified Mandatory Access Control Kernel")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
smk_write_relabel_self() frees memory from the task's credentials with
no locking, which can easily cause a use-after-free because multiple
tasks can share the same credentials structure.
Fix this by using prepare_creds() and commit_creds() to correctly modify
the task's credentials.
Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self":
#include <fcntl.h>
#include <pthread.h>
#include <unistd.h>
static void *thrproc(void *arg)
{
int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY);
for (;;) write(fd, "foo", 3);
}
int main()
{
pthread_t t;
pthread_create(&t, NULL, thrproc, NULL);
thrproc(NULL);
}
Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com
Fixes: 38416e5393 ("Smack: limited capability for changing process label")
Cc: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Pull notification queue from David Howells:
"This adds a general notification queue concept and adds an event
source for keys/keyrings, such as linking and unlinking keys and
changing their attributes.
Thanks to Debarshi Ray, we do have a pull request to use this to fix a
problem with gnome-online-accounts - as mentioned last time:
https://gitlab.gnome.org/GNOME/gnome-online-accounts/merge_requests/47
Without this, g-o-a has to constantly poll a keyring-based kerberos
cache to find out if kinit has changed anything.
[ There are other notification pending: mount/sb fsinfo notifications
for libmount that Karel Zak and Ian Kent have been working on, and
Christian Brauner would like to use them in lxc, but let's see how
this one works first ]
LSM hooks are included:
- A set of hooks are provided that allow an LSM to rule on whether or
not a watch may be set. Each of these hooks takes a different
"watched object" parameter, so they're not really shareable. The
LSM should use current's credentials. [Wanted by SELinux & Smack]
- A hook is provided to allow an LSM to rule on whether or not a
particular message may be posted to a particular queue. This is
given the credentials from the event generator (which may be the
system) and the watch setter. [Wanted by Smack]
I've provided SELinux and Smack with implementations of some of these
hooks.
WHY
===
Key/keyring notifications are desirable because if you have your
kerberos tickets in a file/directory, your Gnome desktop will monitor
that using something like fanotify and tell you if your credentials
cache changes.
However, we also have the ability to cache your kerberos tickets in
the session, user or persistent keyring so that it isn't left around
on disk across a reboot or logout. Keyrings, however, cannot currently
be monitored asynchronously, so the desktop has to poll for it - not
so good on a laptop. This facility will allow the desktop to avoid the
need to poll.
DESIGN DECISIONS
================
- The notification queue is built on top of a standard pipe. Messages
are effectively spliced in. The pipe is opened with a special flag:
pipe2(fds, O_NOTIFICATION_PIPE);
The special flag has the same value as O_EXCL (which doesn't seem
like it will ever be applicable in this context)[?]. It is given up
front to make it a lot easier to prohibit splice&co from accessing
the pipe.
[?] Should this be done some other way? I'd rather not use up a new
O_* flag if I can avoid it - should I add a pipe3() system call
instead?
The pipe is then configured::
ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, queue_depth);
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
Messages are then read out of the pipe using read().
- It should be possible to allow write() to insert data into the
notification pipes too, but this is currently disabled as the
kernel has to be able to insert messages into the pipe *without*
holding pipe->mutex and the code to make this work needs careful
auditing.
- sendfile(), splice() and vmsplice() are disabled on notification
pipes because of the pipe->mutex issue and also because they
sometimes want to revert what they just did - but one or more
notification messages might've been interleaved in the ring.
- The kernel inserts messages with the wait queue spinlock held. This
means that pipe_read() and pipe_write() have to take the spinlock
to update the queue pointers.
- Records in the buffer are binary, typed and have a length so that
they can be of varying size.
This allows multiple heterogeneous sources to share a common
buffer; there are 16 million types available, of which I've used
just a few, so there is scope for others to be used. Tags may be
specified when a watchpoint is created to help distinguish the
sources.
- Records are filterable as types have up to 256 subtypes that can be
individually filtered. Other filtration is also available.
- Notification pipes don't interfere with each other; each may be
bound to a different set of watches. Any particular notification
will be copied to all the queues that are currently watching for it
- and only those that are watching for it.
- When recording a notification, the kernel will not sleep, but will
rather mark a queue as having lost a message if there's
insufficient space. read() will fabricate a loss notification
message at an appropriate point later.
- The notification pipe is created and then watchpoints are attached
to it, using one of:
keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);
watch_mount(AT_FDCWD, "/", 0, fd, 0x02);
watch_sb(AT_FDCWD, "/mnt", 0, fd, 0x03);
where in both cases, fd indicates the queue and the number after is
a tag between 0 and 255.
- Watches are removed if either the notification pipe is destroyed or
the watched object is destroyed. In the latter case, a message will
be generated indicating the enforced watch removal.
Things I want to avoid:
- Introducing features that make the core VFS dependent on the
network stack or networking namespaces (ie. usage of netlink).
- Dumping all this stuff into dmesg and having a daemon that sits
there parsing the output and distributing it as this then puts the
responsibility for security into userspace and makes handling
namespaces tricky. Further, dmesg might not exist or might be
inaccessible inside a container.
- Letting users see events they shouldn't be able to see.
TESTING AND MANPAGES
====================
- The keyutils tree has a pipe-watch branch that has keyctl commands
for making use of notifications. Proposed manual pages can also be
found on this branch, though a couple of them really need to go to
the main manpages repository instead.
If the kernel supports the watching of keys, then running "make
test" on that branch will cause the testing infrastructure to spawn
a monitoring process on the side that monitors a notifications pipe
for all the key/keyring changes induced by the tests and they'll
all be checked off to make sure they happened.
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/log/?h=pipe-watch
- A test program is provided (samples/watch_queue/watch_test) that
can be used to monitor for keyrings, mount and superblock events.
Information on the notifications is simply logged to stdout"
* tag 'notifications-20200601' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
smack: Implement the watch_key and post_notification hooks
selinux: Implement the watch_key security hook
keys: Make the KEY_NEED_* perms an enum rather than a mask
pipe: Add notification lossage handling
pipe: Allow buffers to be marked read-whole-or-error for notifications
Add sample notification program
watch_queue: Add a key/keyring notification facility
security: Add hooks to rule on setting a watch
pipe: Add general notification queue support
pipe: Add O_NOTIFICATION_PIPE
security: Add a hook for the point of notification insertion
uapi: General notification queue definitions
Pull execve updates from Eric Biederman:
"Last cycle for the Nth time I ran into bugs and quality of
implementation issues related to exec that could not be easily be
fixed because of the way exec is implemented. So I have been digging
into exec and cleanup up what I can.
I don't think I have exec sorted out enough to fix the issues I
started with but I have made some headway this cycle with 4 sets of
changes.
- promised cleanups after introducing exec_update_mutex
- trivial cleanups for exec
- control flow simplifications
- remove the recomputation of bprm->cred
The net result is code that is a bit easier to understand and work
with and a decrease in the number of lines of code (if you don't count
the added tests)"
* 'exec-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (24 commits)
exec: Compute file based creds only once
exec: Add a per bprm->file version of per_clear
binfmt_elf_fdpic: fix execfd build regression
selftests/exec: Add binfmt_script regression test
exec: Remove recursion from search_binary_handler
exec: Generic execfd support
exec/binfmt_script: Don't modify bprm->buf and then return -ENOEXEC
exec: Move the call of prepare_binprm into search_binary_handler
exec: Allow load_misc_binary to call prepare_binprm unconditionally
exec: Convert security_bprm_set_creds into security_bprm_repopulate_creds
exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds
exec: Teach prepare_exec_creds how exec treats uids & gids
exec: Set the point of no return sooner
exec: Move handling of the point of no return to the top level
exec: Run sync_mm_rss before taking exec_update_mutex
exec: Fix spelling of search_binary_handler in a comment
exec: Move the comment from above de_thread to above unshare_sighand
exec: Rename flush_old_exec begin_new_exec
exec: Move most of setup_new_exec into flush_old_exec
exec: In setup_new_exec cache current in the local variable me
...
Today security_bprm_set_creds has several implementations:
apparmor_bprm_set_creds, cap_bprm_set_creds, selinux_bprm_set_creds,
smack_bprm_set_creds, and tomoyo_bprm_set_creds.
Except for cap_bprm_set_creds they all test bprm->called_set_creds and
return immediately if it is true. The function cap_bprm_set_creds
ignores bprm->calld_sed_creds entirely.
Create a new LSM hook security_bprm_creds_for_exec that is called just
before prepare_binprm in __do_execve_file, resulting in a LSM hook
that is called exactly once for the entire of exec. Modify the bits
of security_bprm_set_creds that only want to be called once per exec
into security_bprm_creds_for_exec, leaving only cap_bprm_set_creds
behind.
Remove bprm->called_set_creds all of it's former users have been moved
to security_bprm_creds_for_exec.
Add or upate comments a appropriate to bring them up to date and
to reflect this change.
Link: https://lkml.kernel.org/r/87v9kszrzh.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com> # For the LSM and Smack bits
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Implement the watch_key security hook in Smack to make sure that a key
grants the caller Read permission in order to set a watch on a key.
Also implement the post_notification security hook to make sure that the
notification source is granted Write permission by the watch queue.
For the moment, the watch_devices security hook is left unimplemented as
it's not obvious what the object should be since the queue is global and
didn't previously exist.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Since the meaning of combining the KEY_NEED_* constants is undefined, make
it so that you can't do that by turning them into an enum.
The enum is also given some extra values to represent special
circumstances, such as:
(1) The '0' value is reserved and causes a warning to trap the parameter
being unset.
(2) The key is to be unlinked and we require no permissions on it, only
the keyring, (this replaces the KEY_LOOKUP_FOR_UNLINK flag).
(3) An override due to CAP_SYS_ADMIN.
(4) An override due to an instantiation token being present.
(5) The permissions check is being deferred to later key_permission()
calls.
The extra values give the opportunity for LSMs to audit these situations.
[Note: This really needs overhauling so that lookup_user_key() tells
key_task_permission() and the LSM what operation is being done and leaves
it to those functions to decide how to map that onto the available
permits. However, I don't really want to make these change in the middle
of the notifications patchset.]
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
cc: Paul Moore <paul@paul-moore.com>
cc: Stephen Smalley <stephen.smalley.work@gmail.com>
cc: Casey Schaufler <casey@schaufler-ca.com>
cc: keyrings@vger.kernel.org
cc: selinux@vger.kernel.org
commit a269434d2f ("LSM: separate LSM_AUDIT_DATA_DENTRY from LSM_AUDIT_DATA_PATH")
left behind this, remove it.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
"smk_lock" mutex is used during inode instantiation in
smack_d_instantiate()function. It has been used to avoid
simultaneous access on same inode security structure.
Since smack related initialization is done only once i.e during
inode creation. If the inode has already been instantiated then
smack_d_instantiate() function just returns without doing
anything.
So it means mutex lock is required only during inode creation.
But since 2 processes can't create same inodes or files
simultaneously. Also linking or some other file operation can't
be done simultaneously when the file is getting created since
file lookup will fail before dentry inode linkup which is done
after smack initialization.
So no mutex lock is required in inode_smack structure.
It will save memory as well as improve some performance.
If 40000 inodes are created in system, it will save 1.5 MB on
32-bit systems & 2.8 MB on 64-bit systems.
Signed-off-by: Vishal Goel <vishal.goel@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
The mix of IS_ENABLED() and #ifdef checks has left a combination
that causes a warning about an unused variable:
security/smack/smack_lsm.c: In function 'smack_socket_connect':
security/smack/smack_lsm.c:2838:24: error: unused variable 'sip' [-Werror=unused-variable]
2838 | struct sockaddr_in6 *sip = (struct sockaddr_in6 *)sap;
Change the code to use C-style checks consistently so the compiler
can handle it correctly.
Fixes: 87fbfffcc8 ("broken ping to ipv6 linklocal addresses on debian buster")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Pull vfs file system parameter updates from Al Viro:
"Saner fs_parser.c guts and data structures. The system-wide registry
of syntax types (string/enum/int32/oct32/.../etc.) is gone and so is
the horror switch() in fs_parse() that would have to grow another case
every time something got added to that system-wide registry.
New syntax types can be added by filesystems easily now, and their
namespace is that of functions - not of system-wide enum members. IOW,
they can be shared or kept private and if some turn out to be widely
useful, we can make them common library helpers, etc., without having
to do anything whatsoever to fs_parse() itself.
And we already get that kind of requests - the thing that finally
pushed me into doing that was "oh, and let's add one for timeouts -
things like 15s or 2h". If some filesystem really wants that, let them
do it. Without somebody having to play gatekeeper for the variants
blessed by direct support in fs_parse(), TYVM.
Quite a bit of boilerplate is gone. And IMO the data structures make a
lot more sense now. -200LoC, while we are at it"
* 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (25 commits)
tmpfs: switch to use of invalfc()
cgroup1: switch to use of errorfc() et.al.
procfs: switch to use of invalfc()
hugetlbfs: switch to use of invalfc()
cramfs: switch to use of errofc() et.al.
gfs2: switch to use of errorfc() et.al.
fuse: switch to use errorfc() et.al.
ceph: use errorfc() and friends instead of spelling the prefix out
prefix-handling analogues of errorf() and friends
turn fs_param_is_... into functions
fs_parse: handle optional arguments sanely
fs_parse: fold fs_parameter_desc/fs_parameter_spec
fs_parser: remove fs_parameter_description name field
add prefix to fs_context->log
ceph_parse_param(), ceph_parse_mon_ips(): switch to passing fc_log
new primitive: __fs_parse()
switch rbd and libceph to p_log-based primitives
struct p_log, variants of warnf() et.al. taking that one instead
teach logfc() to handle prefices, give it saner calling conventions
get rid of cg_invalf()
...
I am seeing ping failures to IPv6 linklocal addresses with Debian
buster. Easiest example to reproduce is:
$ ping -c1 -w1 ff02::1%eth1
connect: Invalid argument
$ ping -c1 -w1 ff02::1%eth1
PING ff02::01%eth1(ff02::1%eth1) 56 data bytes
64 bytes from fe80::e0:f9ff:fe0c:37%eth1: icmp_seq=1 ttl=64 time=0.059 ms
git bisect traced the failure to
commit b9ef5513c9 ("smack: Check address length before reading address family")
Arguably ping is being stupid since the buster version is not setting
the address family properly (ping on stretch for example does):
$ strace -e connect ping6 -c1 -w1 ff02::1%eth1
connect(5, {sa_family=AF_UNSPEC,
sa_data="\4\1\0\0\0\0\377\2\0\0\0\0\0\0\0\0\0\0\0\0\0\1\3\0\0\0"}, 28)
= -1 EINVAL (Invalid argument)
but the command works fine on kernels prior to this commit, so this is
breakage which goes against the Linux paradigm of "don't break userspace"
Cc: stable@vger.kernel.org
Reported-by: David Ahern <dsahern@gmail.com>
Suggested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
security/smack/smack_lsm.c | 41 +++++++++++++++++++----------------------
1 file changed, 19 insertions(+), 22 deletions(-)
Pull smack updates from Casey Schaufler:
"Four patches for v5.4. Nothing is major.
All but one are in response to mechanically detected potential issues.
The remaining patch cleans up kernel-doc notations"
* tag 'smack-for-5.4-rc1' of git://github.com/cschaufler/smack-next:
smack: use GFP_NOFS while holding inode_smack::smk_lock
security: smack: Fix possible null-pointer dereferences in smack_socket_sock_rcv_skb()
smack: fix some kernel-doc notations
Smack: Don't ignore other bprm->unsafe flags if LSM_UNSAFE_PTRACE is set
inode_smack::smk_lock is taken during smack_d_instantiate(), which is
called during a filesystem transaction when creating a file on ext4.
Therefore to avoid a deadlock, all code that takes this lock must use
GFP_NOFS, to prevent memory reclaim from waiting for the filesystem
transaction to complete.
Reported-by: syzbot+0eefc1e06a77d327a056@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
In smack_socket_sock_rcv_skb(), there is an if statement
on line 3920 to check whether skb is NULL:
if (skb && skb->secmark != 0)
This check indicates skb can be NULL in some cases.
But on lines 3931 and 3932, skb is used:
ad.a.u.net->netif = skb->skb_iif;
ipv6_skb_to_auditdata(skb, &ad.a, NULL);
Thus, possible null-pointer dereferences may occur when skb is NULL.
To fix these possible bugs, an if statement is added to check skb.
These bugs are found by a static analysis tool STCheck written by us.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
There is a logic bug in the current smack_bprm_set_creds():
If LSM_UNSAFE_PTRACE is set, but the ptrace state is deemed to be
acceptable (e.g. because the ptracer detached in the meantime), the other
->unsafe flags aren't checked. As far as I can tell, this means that
something like the following could work (but I haven't tested it):
- task A: create task B with fork()
- task B: set NO_NEW_PRIVS
- task B: install a seccomp filter that makes open() return 0 under some
conditions
- task B: replace fd 0 with a malicious library
- task A: attach to task B with PTRACE_ATTACH
- task B: execve() a file with an SMACK64EXEC extended attribute
- task A: while task B is still in the middle of execve(), exit (which
destroys the ptrace relationship)
Make sure that if any flags other than LSM_UNSAFE_PTRACE are set in
bprm->unsafe, we reject the execve().
Cc: stable@vger.kernel.org
Fixes: 5663884caa ("Smack: unify all ptrace accesses in the smack")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Pull vfs mount updates from Al Viro:
"The first part of mount updates.
Convert filesystems to use the new mount API"
* 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
mnt_init(): call shmem_init() unconditionally
constify ksys_mount() string arguments
don't bother with registering rootfs
init_rootfs(): don't bother with init_ramfs_fs()
vfs: Convert smackfs to use the new mount API
vfs: Convert selinuxfs to use the new mount API
vfs: Convert securityfs to use the new mount API
vfs: Convert apparmorfs to use the new mount API
vfs: Convert openpromfs to use the new mount API
vfs: Convert xenfs to use the new mount API
vfs: Convert gadgetfs to use the new mount API
vfs: Convert oprofilefs to use the new mount API
vfs: Convert ibmasmfs to use the new mount API
vfs: Convert qib_fs/ipathfs to use the new mount API
vfs: Convert efivarfs to use the new mount API
vfs: Convert configfs to use the new mount API
vfs: Convert binfmt_misc to use the new mount API
convenience helper: get_tree_single()
convenience helper get_tree_nodev()
vfs: Kill sget_userns()
...
