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, 31 insertions, 0 deletions

diff --git a/tools/perf/util/cache.h b/tools/perf/util/cache.h
new file mode 100644
index 000000000..0b61840d4
--- /dev/null
+++ b/tools/perf/util/cache.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_CACHE_H
+#define __PERF_CACHE_H
+
+#include "strbuf.h"
+#include <subcmd/pager.h>
+#include "../ui/ui.h"
+
+#include <linux/compiler.h>
+#include <linux/string.h>
+
+#define CMD_EXEC_PATH "--exec-path"
+#define CMD_DEBUGFS_DIR "--debugfs-dir="
+
+#define EXEC_PATH_ENVIRONMENT "PERF_EXEC_PATH"
+#define PERF_DEBUGFS_ENVIRONMENT "PERF_DEBUGFS_DIR"
+#define PERF_TRACEFS_ENVIRONMENT "PERF_TRACEFS_DIR"
+#define PERF_PAGER_ENVIRONMENT "PERF_PAGER"
+
+int split_cmdline(char *cmdline, const char ***argv);
+
+#define alloc_nr(x) (((x)+16)*3/2)
+
+static inline int is_absolute_path(const char *path)
+{
+	return path[0] == '/';
+}
+
+char *mkpath(char *path_buf, size_t sz, const char *fmt, ...) __printf(3, 4);
+
+#endif /* __PERF_CACHE_H */