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, 141 insertions, 0 deletions

diff --git a/security/apparmor/procattr.c b/security/apparmor/procattr.c
new file mode 100644
index 000000000..c07b6e8fd
--- /dev/null
+++ b/security/apparmor/procattr.c
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor /proc/<pid>/attr/ interface functions
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ */
+
+#include "include/apparmor.h"
+#include "include/cred.h"
+#include "include/policy.h"
+#include "include/policy_ns.h"
+#include "include/domain.h"
+#include "include/procattr.h"
+
+
+/**
+ * aa_getprocattr - Return the label information for @label
+ * @label: the label to print label info about  (NOT NULL)
+ * @string: Returns - string containing the label info (NOT NULL)
+ * @newline: indicates that a newline should be added
+ *
+ * Requires: label != NULL && string != NULL
+ *
+ * Creates a string containing the label information for @label.
+ *
+ * Returns: size of string placed in @string else error code on failure
+ */
+int aa_getprocattr(struct aa_label *label, char **string, bool newline)
+{
+	struct aa_ns *ns = labels_ns(label);
+	struct aa_ns *current_ns = aa_get_current_ns();
+	int len;
+
+	if (!aa_ns_visible(current_ns, ns, true)) {
+		aa_put_ns(current_ns);
+		return -EACCES;
+	}
+
+	len = aa_label_snxprint(NULL, 0, current_ns, label,
+				FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
+				FLAG_HIDDEN_UNCONFINED);
+	AA_BUG(len < 0);
+
+	*string = kmalloc(len + 2, GFP_KERNEL);
+	if (!*string) {
+		aa_put_ns(current_ns);
+		return -ENOMEM;
+	}
+
+	len = aa_label_snxprint(*string, len + 2, current_ns, label,
+				FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
+				FLAG_HIDDEN_UNCONFINED);
+	if (len < 0) {
+		kfree(*string);
+		*string = NULL;
+		aa_put_ns(current_ns);
+		return len;
+	}
+
+	if (newline)
+		(*string)[len++] = '\n';
+	(*string)[len] = 0;
+
+	aa_put_ns(current_ns);
+	return len;
+}
+
+/**
+ * split_token_from_name - separate a string of form  <token>^<name>
+ * @op: operation being checked
+ * @args: string to parse  (NOT NULL)
+ * @token: stores returned parsed token value  (NOT NULL)
+ *
+ * Returns: start position of name after token else NULL on failure
+ */
+static char *split_token_from_name(const char *op, char *args, u64 *token)
+{
+	char *name;
+
+	*token = simple_strtoull(args, &name, 16);
+	if ((name == args) || *name != '^') {
+		AA_ERROR("%s: Invalid input '%s'", op, args);
+		return ERR_PTR(-EINVAL);
+	}
+
+	name++;			/* skip ^ */
+	if (!*name)
+		name = NULL;
+	return name;
+}
+
+/**
+ * aa_setprocattr_changehat - handle procattr interface to change_hat
+ * @args: args received from writing to /proc/<pid>/attr/current (NOT NULL)
+ * @size: size of the args
+ * @flags: set of flags governing behavior
+ *
+ * Returns: %0 or error code if change_hat fails
+ */
+int aa_setprocattr_changehat(char *args, size_t size, int flags)
+{
+	char *hat;
+	u64 token;
+	const char *hats[16];		/* current hard limit on # of names */
+	int count = 0;
+
+	hat = split_token_from_name(OP_CHANGE_HAT, args, &token);
+	if (IS_ERR(hat))
+		return PTR_ERR(hat);
+
+	if (!hat && !token) {
+		AA_ERROR("change_hat: Invalid input, NULL hat and NULL magic");
+		return -EINVAL;
+	}
+
+	if (hat) {
+		/* set up hat name vector, args guaranteed null terminated
+		 * at args[size] by setprocattr.
+		 *
+		 * If there are multiple hat names in the buffer each is
+		 * separated by a \0.  Ie. userspace writes them pre tokenized
+		 */
+		char *end = args + size;
+		for (count = 0; (hat < end) && count < 16; ++count) {
+			char *next = hat + strlen(hat) + 1;
+			hats[count] = hat;
+			AA_DEBUG(DEBUG_DOMAIN,
+				 "%s: (pid %d) Magic 0x%llx count %d hat '%s'\n"
+				 , __func__, current->pid, token, count, hat);
+			hat = next;
+		}
+	} else
+		AA_DEBUG(DEBUG_DOMAIN,
+			 "%s: (pid %d) Magic 0x%llx count %d Hat '%s'\n",
+			 __func__, current->pid, token, count, "<NULL>");
+
+	return aa_change_hat(hats, count, token, flags);
+}