Commit Graph

29 Commits

Author SHA1 Message Date
Sudip Mukherjee
54555919e8 tty: audit: remove unused variable
While building with W=1 we were getting build warning:
drivers/tty/tty_audit.c:149:16: warning: variable 'sessionid' set but not used

The local variable sessionid was only assigned the value of
current->sessionid but was never reused. On further inspection it turned
out that there is no need of audit_get_loginuid() also.

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-03-07 16:11:14 -08:00
Peter Hurley
55b6314a17 tty: audit: Poison tty_audit_buf while process exits
Warn if tty_audit_buf use is attempted after tty_audit_exit() has
already freed it.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
82b5c93a00 tty: audit: Always push audit buffer before TIOCSTI
The data read from another tty may be relevant to the action of
the TIOCSTI ioctl; log the audit buffer immediately.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
f17c366274 tty: audit: Check audit enable first
Audit is unlikely to be enabled; check first to exit asap.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
fbaa122718 tty: audit: Simplify first-use allocation
The first-use tty audit buffer allocation is a potential race
amongst multiple attempts at 'first-use'; only one 'winner' is
acceptable.

The successful buffer assignment occurs if tty_audit_buf == NULL
(which will also be the return from cmpxchg()); otherwise, another
racer 'won' and this buffer allocation is freed.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
5493090fc2 tty: audit: Remove tty_audit_buf reference counting
When tty_audit_exit() is called from do_exit(), the process is
single-threaded. Since the tty_audit_buf is only shared by threads
of a process, no other thread can be concurrently accessing the
tty_audit_buf during or after tty_audit_exit().

Thus, no other thread can be holding an extra tty_audit_buf reference
which would prevent tty_audit_exit() from freeing the tty_audit_buf.
As that is the only purpose of the ref counting, remove the reference
counting and free the tty_audit_buf directly.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
5c8b3185c4 tty: audit: Remove false memory optimization
The tty audit buffer is allocated at first use and not freed until
the process exits. If tty audit is turned off after the audit buffer
has been allocated, no effort is made to release the buffer.
So re-checking if tty audit has just been turned off when tty audit
was just on is false optimization; the likelihood of triggering this
condition is exceedingly small.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
2e28d38ae1 tty: audit: Handle tty audit enable atomically
The audit_tty and audit_tty_log_passwd fields are actually bool
values, so merge into single memory location to access atomically.

NB: audit log operations may still occur after tty audit is disabled
which is consistent with the existing functionality

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
4d240b6442 tty: audit: Track tty association with dev_t
Use dev_t instead of separate major/minor fields to track tty
audit buffer association.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
37282a7795 tty: audit: Combine push functions
tty_audit_push() and tty_audit_push_current() perform identical
tasks; eliminate the tty_audit_push() implementation and the
tty_audit_push_current() name.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
b50819f437 tty: audit: Ignore current association for audit push
In canonical read mode, each line read and logged is pushed separately
with tty_audit_push(). For all single-threaded processes and multi-threaded
processes reading from only one tty, this patch has no effect; the last line
read will still be the entry pushed to the audit log because the tty
association cannot have changed between tty_audit_add_data() and
tty_audit_push().

For multi-threaded processes reading from different ttys concurrently,
the audit log will have mixed log entries anyway. Consider two ttys
audited concurrently:

CPU0                           CPU1
----------                     ------------
tty_audit_add_data(ttyA)
                               tty_audit_add_data(ttyB)
tty_audit_push()
                               tty_audit_add_data(ttyB)
                               tty_audit_push()

This patch will now cause the ttyB output to be split into separate
audit log entries.

However, this possibility is equally likely without this patch:

CPU0                           CPU1
----------                     ------------
                               tty_audit_add_data(ttyB)
tty_audit_add_data(ttyA)
tty_audit_push()
                               tty_audit_add_data(ttyB)
                               tty_audit_push()

Mixed canonical and non-canonical reads have similar races.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
f229c2c161 tty: audit: Take siglock directly
lock_task_sighand() is for situations where the struct task_struct*
may disappear while trying to deref the sighand; this never applies
to 'current'.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
a75c9b0912 tty: audit: Defer audit buffer association
The tty audit buffer used to audit/record tty input is allocated on
the process's first call to tty_audit_add_data(), and not freed until
the process exits. On each call to tty_audit_add_data(), the current
tty is compared (by major:minor) with the last tty associated with
the audit buffer, and if the tty has changed the existing data is
logged to the audit log. The audit buffer is then re-associated with
the new tty.

Currently, the audit buffer is immediately associated with the tty;
however, the association must be re-checked when the buffer is locked
prior to copying the tty input. This extra step is always necessary,
since a concurrent read of a different tty by another thread of the
process may have used the buffer in between allocation and buffer
lock.

Rather than associate the audit buffer with the tty at allocation,
leave the buffer initially un-associated (null dev_t); simply let the
re-association check also perform the initial association.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
309426ae69 tty: audit: Remove icanon mode from call chain
The tty termios bits cannot change while n_tty_read() is in the
i/o loop; the termios_rwsem ensures mutual exclusion with termios
changes in n_tty_set_termios(). Check L_ICANON() directly and
eliminate icanon parameter.

NB: tty_audit_add_data() => tty_audit_buf_get() => tty_audit_buf_alloc()
is a single path; ie., tty_audit_buf_get() and tty_audit_buf_alloc()
have no other callers.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
d7c0ba40eb tty: audit: Early-out pty master reads earlier
Reads from pty masters are not logged; early-out before taking
locks.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 16:41:04 -08:00
Peter Hurley
6b2a3d628a tty: audit: Fix audit source
The data to audit/record is in the 'from' buffer (ie., the input
read buffer).

Fixes: 72586c6061 ("n_tty: Fix auditing support for cannonical mode")
Cc: stable <stable@vger.kernel.org> # 4.1+
Cc: Miloslav Trmač <mitr@redhat.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Laura Abbott <labbott@fedoraproject.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-11-20 16:19:54 -08:00
Richard Guy Briggs
f1dc4867ff audit: anchor all pid references in the initial pid namespace
Store and log all PIDs with reference to the initial PID namespace and
use the access functions task_pid_nr() and task_tgid_nr() for task->pid
and task->tgid.

Cc: "Eric W. Biederman" <ebiederm@xmission.com>
(informed by ebiederman's c776b5d2)
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
2014-03-20 10:11:55 -04:00
Eric Paris
4440e85481 audit: convert all sessionid declaration to unsigned int
Right now the sessionid value in the kernel is a combination of u32,
int, and unsigned int.  Just use unsigned int throughout.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
2014-01-13 22:31:46 -05:00
Eric Paris
bee0a224e7 audit: do not needlessly take a lock in tty_audit_exit
We were doing spin_lock_irq and spin_unlock_irq.  This is STOOPID.

If we were in interupt context we were already screwed and called
panic() in do_exit().  So the irq stuff is useless.  Also, these values
can only be changed by receiving a netlink message from current.  Since
we are in do_exit() clearly we aren't in the syscall sending the netlink
message to change these values.  Thus, just read them and go with it.

Signed-off-by: Eric Paris <eparis@redhat.com>
2013-04-30 15:31:28 -04:00
Eric Paris
2ce88dd042 audit: do not needlessly take a spinlock in copy_signal
current->signal->audit_* can only change from a netlink message from
current.  Obviously in this case we cannot be handling a netlink message
from current.  So there is no change these can change under us.  No need
to take a lock to read them.

Signed-off-by: Eric Paris <eparis@redhat.com>
2013-04-30 15:31:28 -04:00
Richard Guy Briggs
46e959ea29 audit: add an option to control logging of passwords with pam_tty_audit
Most commands are entered one line at a time and processed as complete lines
in non-canonical mode.  Commands that interactively require a password, enter
canonical mode to do this while shutting off echo.  This pair of features
(icanon and !echo) can be used to avoid logging passwords by audit while still
logging the rest of the command.

Adding a member (log_passwd) to the struct audit_tty_status passed in by
pam_tty_audit allows control of canonical mode without echo per task.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
2013-04-30 15:31:28 -04:00
Eric Paris
bde02ca858 audit: use spin_lock_irqsave/restore in audit tty code
Some of the callers of the audit tty function use spin_lock_irqsave/restore.
We were using the forced always enable version, which seems really bad.
Since I don't know every one of these code paths well enough, it makes
sense to just switch everything to the safe version.  Maybe it's a
little overzealous, but it's a lot better than an unlucky deadlock when
we return to a caller with irq enabled and they expect it to be
disabled.

Signed-off-by: Eric Paris <eparis@redhat.com>
2013-04-30 15:31:28 -04:00
Eric Paris
152f497b9b audit: push loginuid and sessionid processing down
Since we are always current, we can push a lot of this stuff to the
bottom and get rid of useless interfaces and arguments.

Signed-off-by: Eric Paris <eparis@redhat.com>
2013-04-30 15:31:28 -04:00
Eric Paris
dc9eb698f4 audit: stop pushing loginid, uid, sessionid as arguments
We always use current.  Stop pulling this when the skb comes in and
pushing it around as arguments.  Just get it at the end when you need
it.

Signed-off-by: Eric Paris <eparis@redhat.com>
2013-04-30 15:31:28 -04:00
Jiri Slaby
6c633f27cc TTY: audit, stop accessing tty->icount
This is a private member of n_tty. Stop accessing it. Instead, take is
as an argument.

This is needed to allow clean switch of the private members to a
separate private structure of n_tty.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-10-22 16:50:54 -07:00
Eric W. Biederman
cca080d9b6 userns: Convert audit to work with user namespaces enabled
- Explicitly format uids gids in audit messges in the initial user
  namespace. This is safe because auditd is restrected to be in
  the initial user namespace.

- Convert audit_sig_uid into a kuid_t.

- Enable building the audit code and user namespaces at the same time.

The net result is that the audit subsystem now uses kuid_t and kgid_t whenever
possible making it almost impossible to confuse a raw uid_t with a kuid_t
preventing bugs.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-09-18 01:00:26 -07:00
Eric W. Biederman
e1760bd5ff userns: Convert the audit loginuid to be a kuid
Always store audit loginuids in type kuid_t.

Print loginuids by converting them into uids in the appropriate user
namespace, and then printing the resulting uid.

Modify audit_get_loginuid to return a kuid_t.

Modify audit_set_loginuid to take a kuid_t.

Modify /proc/<pid>/loginuid on read to convert the loginuid into the
user namespace of the opener of the file.

Modify /proc/<pid>/loginud on write to convert the loginuid
rom the user namespace of the opener of the file.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Paul Moore <paul@paul-moore.com> ?
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-09-17 18:08:54 -07:00
Xiaotian Feng
00bff392c8 tty_audit: fix tty_audit_add_data live lock on audit disabled
The current tty_audit_add_data code:

        do {
                size_t run;

                run = N_TTY_BUF_SIZE - buf->valid;
                if (run > size)
                        run = size;
                memcpy(buf->data + buf->valid, data, run);
                buf->valid += run;
                data += run;
                size -= run;
                if (buf->valid == N_TTY_BUF_SIZE)
                        tty_audit_buf_push_current(buf);
        } while (size != 0);

If the current buffer is full, kernel will then call tty_audit_buf_push_current
to empty the buffer. But if we disabled audit at the same time, tty_audit_buf_push()
returns immediately if audit_enabled is zero.  Without emptying the buffer.
With obvious effect on tty_audit_add_data() that ends up spinning in that loop,
copying 0 bytes at each iteration and attempting to push each time without any effect.
Holding the lock all along.

Suggested-by: Alexander Viro <aviro@redhat.com>
Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-03-07 12:04:50 -08:00
Greg Kroah-Hartman
96fd7ce58f TTY: create drivers/tty and move the tty core files there
The tty code should be in its own subdirectory and not in the char
driver with all of the cruft that is currently there.

Based on work done by Arnd Bergmann <arnd@arndb.de>

Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-11-05 08:10:33 -07:00