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, 89 insertions, 0 deletions

diff --git a/lib/audit.c b/lib/audit.c
new file mode 100644
index 000000000..bc07fbd3a
--- /dev/null
+++ b/lib/audit.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/audit.h>
+#include <asm/unistd.h>
+
+static unsigned dir_class[] = {
+#include <asm-generic/audit_dir_write.h>
+~0U
+};
+
+static unsigned read_class[] = {
+#include <asm-generic/audit_read.h>
+~0U
+};
+
+static unsigned write_class[] = {
+#include <asm-generic/audit_write.h>
+~0U
+};
+
+static unsigned chattr_class[] = {
+#include <asm-generic/audit_change_attr.h>
+~0U
+};
+
+static unsigned signal_class[] = {
+#include <asm-generic/audit_signal.h>
+~0U
+};
+
+int audit_classify_arch(int arch)
+{
+	if (audit_is_compat(arch))
+		return 1;
+	else
+		return 0;
+}
+
+int audit_classify_syscall(int abi, unsigned syscall)
+{
+	if (audit_is_compat(abi))
+		return audit_classify_compat_syscall(abi, syscall);
+
+	switch (syscall) {
+#ifdef __NR_open
+	case __NR_open:
+		return AUDITSC_OPEN;
+#endif
+#ifdef __NR_openat
+	case __NR_openat:
+		return AUDITSC_OPENAT;
+#endif
+#ifdef __NR_socketcall
+	case __NR_socketcall:
+		return AUDITSC_SOCKETCALL;
+#endif
+#ifdef __NR_execveat
+	case __NR_execveat:
+#endif
+	case __NR_execve:
+		return AUDITSC_EXECVE;
+#ifdef __NR_openat2
+	case __NR_openat2:
+		return AUDITSC_OPENAT2;
+#endif
+	default:
+		return AUDITSC_NATIVE;
+	}
+}
+
+static int __init audit_classes_init(void)
+{
+#ifdef CONFIG_AUDIT_COMPAT_GENERIC
+	audit_register_class(AUDIT_CLASS_WRITE_32, compat_write_class);
+	audit_register_class(AUDIT_CLASS_READ_32, compat_read_class);
+	audit_register_class(AUDIT_CLASS_DIR_WRITE_32, compat_dir_class);
+	audit_register_class(AUDIT_CLASS_CHATTR_32, compat_chattr_class);
+	audit_register_class(AUDIT_CLASS_SIGNAL_32, compat_signal_class);
+#endif
+	audit_register_class(AUDIT_CLASS_WRITE, write_class);
+	audit_register_class(AUDIT_CLASS_READ, read_class);
+	audit_register_class(AUDIT_CLASS_DIR_WRITE, dir_class);
+	audit_register_class(AUDIT_CLASS_CHATTR, chattr_class);
+	audit_register_class(AUDIT_CLASS_SIGNAL, signal_class);
+	return 0;
+}
+
+__initcall(audit_classes_init);