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, 54 insertions, 0 deletions

diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
new file mode 100644
index 000000000..079284120
--- /dev/null
+++ b/fs/pstore/internal.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PSTORE_INTERNAL_H__
+#define __PSTORE_INTERNAL_H__
+
+#include <linux/types.h>
+#include <linux/time.h>
+#include <linux/pstore.h>
+
+extern unsigned int kmsg_bytes;
+
+#ifdef CONFIG_PSTORE_FTRACE
+extern unsigned long decode_ip(unsigned long ip);
+extern void pstore_register_ftrace(void);
+extern void pstore_unregister_ftrace(void);
+ssize_t pstore_ftrace_combine_log(char **dest_log, size_t *dest_log_size,
+				  const char *src_log, size_t src_log_size);
+#else
+static inline void pstore_register_ftrace(void) {}
+static inline void pstore_unregister_ftrace(void) {}
+static inline unsigned long decode_ip(unsigned long ip) { return ip; }
+static inline ssize_t
+pstore_ftrace_combine_log(char **dest_log, size_t *dest_log_size,
+			  const char *src_log, size_t src_log_size)
+{
+	*dest_log_size = 0;
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_PSTORE_PMSG
+extern void pstore_register_pmsg(void);
+extern void pstore_unregister_pmsg(void);
+#else
+static inline void pstore_register_pmsg(void) {}
+static inline void pstore_unregister_pmsg(void) {}
+#endif
+
+extern struct pstore_info *psinfo;
+
+extern void	pstore_set_kmsg_bytes(unsigned int bytes);
+extern void	pstore_get_records(int);
+extern void	pstore_get_backend_records(struct pstore_info *psi,
+					   struct dentry *root, int quiet);
+extern int	pstore_put_backend_records(struct pstore_info *psi);
+extern int	pstore_mkfile(struct dentry *root,
+			      struct pstore_record *record);
+extern void	pstore_record_init(struct pstore_record *record,
+				   struct pstore_info *psi);
+
+/* Called during pstore init/exit. */
+int __init	pstore_init_fs(void);
+void __exit	pstore_exit_fs(void);
+
+#endif