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, 116 insertions, 0 deletions

diff --git a/security/apparmor/ipc.c b/security/apparmor/ipc.c
new file mode 100644
index 000000000..df5712cea
--- /dev/null
+++ b/security/apparmor/ipc.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor ipc mediation
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2017 Canonical Ltd.
+ */
+
+#include <linux/gfp.h>
+
+#include "include/audit.h"
+#include "include/capability.h"
+#include "include/cred.h"
+#include "include/policy.h"
+#include "include/ipc.h"
+#include "include/sig_names.h"
+
+
+static inline int map_signal_num(int sig)
+{
+	if (sig > SIGRTMAX)
+		return SIGUNKNOWN;
+	else if (sig >= SIGRTMIN)
+		return sig - SIGRTMIN + SIGRT_BASE;
+	else if (sig < MAXMAPPED_SIG)
+		return sig_map[sig];
+	return SIGUNKNOWN;
+}
+
+/**
+ * audit_signal_mask - convert mask to permission string
+ * @mask: permission mask to convert
+ *
+ * Returns: pointer to static string
+ */
+static const char *audit_signal_mask(u32 mask)
+{
+	if (mask & MAY_READ)
+		return "receive";
+	if (mask & MAY_WRITE)
+		return "send";
+	return "";
+}
+
+/**
+ * audit_signal_cb() - call back for signal specific audit fields
+ * @ab: audit_buffer  (NOT NULL)
+ * @va: audit struct to audit values of  (NOT NULL)
+ */
+static void audit_signal_cb(struct audit_buffer *ab, void *va)
+{
+	struct common_audit_data *sa = va;
+	struct apparmor_audit_data *ad = aad(sa);
+
+	if (ad->request & AA_SIGNAL_PERM_MASK) {
+		audit_log_format(ab, " requested_mask=\"%s\"",
+				 audit_signal_mask(ad->request));
+		if (ad->denied & AA_SIGNAL_PERM_MASK) {
+			audit_log_format(ab, " denied_mask=\"%s\"",
+					 audit_signal_mask(ad->denied));
+		}
+	}
+	if (ad->signal == SIGUNKNOWN)
+		audit_log_format(ab, "signal=unknown(%d)",
+				 ad->unmappedsig);
+	else if (ad->signal < MAXMAPPED_SIGNAME)
+		audit_log_format(ab, " signal=%s", sig_names[ad->signal]);
+	else
+		audit_log_format(ab, " signal=rtmin+%d",
+				 ad->signal - SIGRT_BASE);
+	audit_log_format(ab, " peer=");
+	aa_label_xaudit(ab, labels_ns(ad->subj_label), ad->peer,
+			FLAGS_NONE, GFP_ATOMIC);
+}
+
+static int profile_signal_perm(const struct cred *cred,
+			       struct aa_profile *profile,
+			       struct aa_label *peer, u32 request,
+			       struct apparmor_audit_data *ad)
+{
+	struct aa_ruleset *rules = profile->label.rules[0];
+	struct aa_perms perms;
+	aa_state_t state;
+
+	if (profile_unconfined(profile))
+		return 0;
+
+	ad->subj_cred = cred;
+	ad->peer = peer;
+	/* TODO: secondary cache check <profile, profile, perm> */
+	state = RULE_MEDIATES(rules, AA_CLASS_SIGNAL);
+	if (!state)
+		return 0;
+	state = aa_dfa_next(rules->policy->dfa, state, ad->signal);
+	aa_label_match(profile, rules, peer, state, false, request, &perms);
+	aa_apply_modes_to_perms(profile, &perms);
+	return aa_check_perms(profile, &perms, request, ad, audit_signal_cb);
+}
+
+int aa_may_signal(const struct cred *subj_cred, struct aa_label *sender,
+		  const struct cred *target_cred, struct aa_label *target,
+		  int sig)
+{
+	struct aa_profile *profile;
+	DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_NONE, AA_CLASS_SIGNAL, OP_SIGNAL);
+
+	ad.signal = map_signal_num(sig);
+	ad.unmappedsig = sig;
+	return xcheck_labels(sender, target, profile,
+			     profile_signal_perm(subj_cred, profile, target,
+						 MAY_WRITE, &ad),
+			     profile_signal_perm(target_cred, profile, sender,
+						 MAY_READ, &ad));
+}