openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 223 insertions, 0 deletions

diff --git a/security/apparmor/capability.c b/security/apparmor/capability.c
new file mode 100644
index 000000000..b9ea6bc45
--- /dev/null
+++ b/security/apparmor/capability.c
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor capability mediation functions
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ */
+
+#include <linux/capability.h>
+#include <linux/errno.h>
+#include <linux/gfp.h>
+#include <linux/security.h>
+#include <linux/timekeeping.h>
+
+#include "include/apparmor.h"
+#include "include/capability.h"
+#include "include/cred.h"
+#include "include/policy.h"
+#include "include/audit.h"
+
+/*
+ * Table of capability names: we generate it from capabilities.h.
+ */
+#include "capability_names.h"
+
+struct aa_sfs_entry aa_sfs_entry_caps[] = {
+	AA_SFS_FILE_STRING("mask", AA_SFS_CAPS_MASK),
+	AA_SFS_FILE_BOOLEAN("extended", 1),
+	{ }
+};
+
+struct audit_cache {
+	const struct cred *ad_subj_cred;
+	/* Capabilities go from 0 to CAP_LAST_CAP */
+	u64 ktime_ns_expiration[CAP_LAST_CAP+1];
+};
+
+static DEFINE_PER_CPU(struct audit_cache, audit_cache);
+
+/**
+ * audit_cb - call back for capability components of audit struct
+ * @ab: audit buffer   (NOT NULL)
+ * @va: audit struct to audit data from  (NOT NULL)
+ */
+static void audit_cb(struct audit_buffer *ab, void *va)
+{
+	struct common_audit_data *sa = va;
+
+	audit_log_format(ab, " capname=");
+	audit_log_untrustedstring(ab, capability_names[sa->u.cap]);
+}
+
+/**
+ * audit_caps - audit a capability
+ * @ad: audit data
+ * @profile: profile being tested for confinement (NOT NULL)
+ * @cap: capability tested
+ * @error: error code returned by test
+ *
+ * Do auditing of capability and handle, audit/complain/kill modes switching
+ * and duplicate message elimination.
+ *
+ * Returns: 0 or ad->error on success,  error code on failure
+ */
+static int audit_caps(struct apparmor_audit_data *ad, struct aa_profile *profile,
+		      int cap, int error)
+{
+	const u64 AUDIT_CACHE_TIMEOUT_NS = 1000*1000*1000; /* 1 second */
+
+	struct aa_ruleset *rules = profile->label.rules[0];
+	struct audit_cache *ent;
+	int type = AUDIT_APPARMOR_AUTO;
+
+	ad->error = error;
+
+	if (likely(!error)) {
+		/* test if auditing is being forced */
+		if (likely((AUDIT_MODE(profile) != AUDIT_ALL) &&
+			   !cap_raised(rules->caps.audit, cap)))
+			return 0;
+		type = AUDIT_APPARMOR_AUDIT;
+	} else if (KILL_MODE(profile) ||
+		   cap_raised(rules->caps.kill, cap)) {
+		type = AUDIT_APPARMOR_KILL;
+	} else if (cap_raised(rules->caps.quiet, cap) &&
+		   AUDIT_MODE(profile) != AUDIT_NOQUIET &&
+		   AUDIT_MODE(profile) != AUDIT_ALL) {
+		/* quiet auditing */
+		return error;
+	}
+
+	/* Do simple duplicate message elimination */
+	ent = &get_cpu_var(audit_cache);
+	/* If the capability was never raised the timestamp check would also catch that */
+	if (ad->subj_cred == ent->ad_subj_cred && ktime_get_ns() <= ent->ktime_ns_expiration[cap]) {
+		put_cpu_var(audit_cache);
+		if (COMPLAIN_MODE(profile))
+			return complain_error(error);
+		return error;
+	} else {
+		put_cred(ent->ad_subj_cred);
+		ent->ad_subj_cred = get_cred(ad->subj_cred);
+		ent->ktime_ns_expiration[cap] = ktime_get_ns() + AUDIT_CACHE_TIMEOUT_NS;
+	}
+	put_cpu_var(audit_cache);
+
+	return aa_audit(type, profile, ad, audit_cb);
+}
+
+/**
+ * profile_capable - test if profile allows use of capability @cap
+ * @profile: profile being enforced    (NOT NULL, NOT unconfined)
+ * @cap: capability to test if allowed
+ * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
+ * @ad: audit data (NOT NULL)
+ *
+ * Returns: 0 if allowed else -EPERM
+ */
+static int profile_capable(struct aa_profile *profile, int cap,
+			   unsigned int opts, struct apparmor_audit_data *ad)
+{
+	struct aa_ruleset *rules = profile->label.rules[0];
+	aa_state_t state;
+	int error;
+
+	state = RULE_MEDIATES(rules, ad->class);
+	if (state) {
+		struct aa_perms perms = { };
+		u32 request;
+
+		/* caps broken into 256 x 32 bit permission chunks */
+		state = aa_dfa_next(rules->policy->dfa, state, cap >> 5);
+		request = 1 << (cap & 0x1f);
+		perms = *aa_lookup_perms(rules->policy, state);
+		aa_apply_modes_to_perms(profile, &perms);
+
+		if (opts & CAP_OPT_NOAUDIT) {
+			if (perms.complain & request)
+				ad->info = "optional: no audit";
+			else
+				ad = NULL;
+		}
+		return aa_check_perms(profile, &perms, request, ad,
+				      audit_cb);
+	}
+
+	/* fallback to old caps mediation that doesn't support conditionals */
+	if (cap_raised(rules->caps.allow, cap) &&
+	    !cap_raised(rules->caps.denied, cap))
+		error = 0;
+	else
+		error = -EPERM;
+
+	if (opts & CAP_OPT_NOAUDIT) {
+		if (!COMPLAIN_MODE(profile))
+			return error;
+		/* audit the cap request in complain mode but note that it
+		 * should be optional.
+		 */
+		ad->info = "optional: no audit";
+	}
+
+	return audit_caps(ad, profile, cap, error);
+}
+
+/**
+ * aa_capable - test permission to use capability
+ * @subj_cred: cred we are testing capability against
+ * @label: label being tested for capability (NOT NULL)
+ * @cap: capability to be tested
+ * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
+ *
+ * Look up capability in profile capability set.
+ *
+ * Returns: 0 on success, or else an error code.
+ */
+int aa_capable(const struct cred *subj_cred, struct aa_label *label,
+	       int cap, unsigned int opts)
+{
+	struct aa_profile *profile;
+	int error = 0;
+	DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_CAP, AA_CLASS_CAP, OP_CAPABLE);
+
+	ad.subj_cred = subj_cred;
+	ad.common.u.cap = cap;
+	error = fn_for_each_confined(label, profile,
+			profile_capable(profile, cap, opts, &ad));
+
+	return error;
+}
+
+kernel_cap_t aa_profile_capget(struct aa_profile *profile)
+{
+	struct aa_ruleset *rules = profile->label.rules[0];
+	aa_state_t state;
+
+	state = RULE_MEDIATES(rules, AA_CLASS_CAP);
+	if (state) {
+		kernel_cap_t caps = CAP_EMPTY_SET;
+		int i;
+
+		/* caps broken into up to 256, 32 bit permission chunks */
+		for (i = 0; i < (CAP_LAST_CAP >> 5); i++) {
+			struct aa_perms perms = { };
+			aa_state_t tmp;
+
+			tmp = aa_dfa_next(rules->policy->dfa, state, i);
+			perms = *aa_lookup_perms(rules->policy, tmp);
+			aa_apply_modes_to_perms(profile, &perms);
+			caps.val |= ((u64)(perms.allow)) << (i * 5);
+			caps.val |= ((u64)(perms.complain)) << (i * 5);
+		}
+		return caps;
+	}
+
+	/* fallback to old caps */
+	if (COMPLAIN_MODE(profile))
+		return CAP_FULL_SET;
+
+	return rules->caps.allow;
+}