/*
 * AppArmor security module
 *
 * This file contains AppArmor ipc mediation
 *
 * Copyright (C) 1998-2008 Novell/SUSE
 * Copyright 2009-2010 Canonical Ltd.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, version 2 of the
 * License.
 */

#include <linux/gfp.h>
#include <linux/ptrace.h>

#include "include/audit.h"
#include "include/capability.h"
#include "include/context.h"
#include "include/policy.h"
#include "include/ipc.h"

/* call back to audit ptrace fields */
static void audit_cb(struct audit_buffer *ab, void *va)
{
	struct common_audit_data *sa = va;
	audit_log_format(ab, " target=");
	audit_log_untrustedstring(ab, sa->aad->target);
}

/**
 * aa_audit_ptrace - do auditing for ptrace
 * @profile: profile being enforced  (NOT NULL)
 * @target: profile being traced (NOT NULL)
 * @error: error condition
 *
 * Returns: %0 or error code
 */
static int aa_audit_ptrace(struct aa_profile *profile,
			   struct aa_profile *target, int error)
{
	struct common_audit_data sa;
	struct apparmor_audit_data aad = {0,};
	sa.type = LSM_AUDIT_DATA_NONE;
	sa.aad = &aad;
	aad.op = OP_PTRACE;
	aad.target = target;
	aad.error = error;

	return aa_audit(AUDIT_APPARMOR_AUTO, profile, GFP_ATOMIC, &sa,
			audit_cb);
}

/**
 * aa_may_ptrace - test if tracer task can trace the tracee
 * @tracer: profile of the task doing the tracing  (NOT NULL)
 * @tracee: task to be traced
 * @mode: whether PTRACE_MODE_READ || PTRACE_MODE_ATTACH
 *
 * Returns: %0 else error code if permission denied or error
 */
int aa_may_ptrace(struct aa_profile *tracer, struct aa_profile *tracee,
		  unsigned int mode)
{
	/* TODO: currently only based on capability, not extended ptrace
	 *       rules,
	 *       Test mode for PTRACE_MODE_READ || PTRACE_MODE_ATTACH
	 */

	if (unconfined(tracer) || tracer == tracee)
		return 0;
	/* log this capability request */
	return aa_capable(tracer, CAP_SYS_PTRACE, 1);
}

/**
 * aa_ptrace - do ptrace permission check and auditing
 * @tracer: task doing the tracing (NOT NULL)
 * @tracee: task being traced (NOT NULL)
 * @mode: ptrace mode either PTRACE_MODE_READ || PTRACE_MODE_ATTACH
 *
 * Returns: %0 else error code if permission denied or error
 */
int aa_ptrace(struct task_struct *tracer, struct task_struct *tracee,
	      unsigned int mode)
{
	/*
	 * tracer can ptrace tracee when
	 * - tracer is unconfined ||
	 *   - tracer is in complain mode
	 *   - tracer has rules allowing it to trace tracee currently this is:
	 *       - confined by the same profile ||
	 *       - tracer profile has CAP_SYS_PTRACE
	 */

	struct aa_profile *tracer_p = aa_get_task_profile(tracer);
	int error = 0;

	if (!unconfined(tracer_p)) {
		struct aa_profile *tracee_p = aa_get_task_profile(tracee);

		error = aa_may_ptrace(tracer_p, tracee_p, mode);
		error = aa_audit_ptrace(tracer_p, tracee_p, error);

		aa_put_profile(tracee_p);
	}
	aa_put_profile(tracer_p);

	return error;
}
ude/trace/events?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>events</a>/<a href='/cgit.cgi/linux/net-next.git/diff/include/trace/events/signal.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>signal.h</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='39cb2c9a316e77f6dfba96c543e55b6672d5a37e'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'include/trace/events/signal.h')</div><table summary='diffstat' class='diffstat'>/tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/trace/events/nmi.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/include/trace/events/nmi.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>98fe974ee4e20121253de7f61fc8d01bdb3821c1</a> /<a href='/cgit.cgi/linux/net-next.git/tree/include/trace/events/nmi.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>include/trace/events/nmi.h</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/trace/events/nmi.h?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/include/trace/events/nmi.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'include/trace/events/nmi.h')</div><table summary='diffstat' class='diffstat'>