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, 50 insertions, 0 deletions

diff --git a/security/lsm.h b/security/lsm.h
new file mode 100644
index 000000000..32f808ad4
--- /dev/null
+++ b/security/lsm.h
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LSM functions
+ */
+
+#ifndef _LSM_H_
+#define _LSM_H_
+
+#include <linux/printk.h>
+#include <linux/lsm_hooks.h>
+#include <linux/lsm_count.h>
+
+/* LSM debugging */
+extern bool lsm_debug;
+#define lsm_pr(...)		pr_info(__VA_ARGS__)
+#define lsm_pr_cont(...)	pr_cont(__VA_ARGS__)
+#define lsm_pr_dbg(...)							\
+	do {								\
+		if (lsm_debug)						\
+			pr_info(__VA_ARGS__);				\
+	} while (0)
+
+/* List of configured LSMs */
+extern unsigned int lsm_active_cnt;
+extern const struct lsm_id *lsm_idlist[];
+
+/* LSM blob configuration */
+extern struct lsm_blob_sizes blob_sizes;
+
+/* LSM blob caches */
+extern struct kmem_cache *lsm_file_cache;
+extern struct kmem_cache *lsm_backing_file_cache;
+extern struct kmem_cache *lsm_inode_cache;
+
+/* LSM blob allocators */
+int lsm_cred_alloc(struct cred *cred, gfp_t gfp);
+int lsm_task_alloc(struct task_struct *task);
+
+/* LSM framework initializers */
+
+#ifdef CONFIG_SECURITYFS
+int securityfs_init(void);
+#else
+static inline int securityfs_init(void)
+{
+	return 0;
+}
+#endif /* CONFIG_SECURITYFS */
+
+#endif /* _LSM_H_ */