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, 48 insertions, 0 deletions

diff --git a/tools/perf/util/mem-info.c b/tools/perf/util/mem-info.c
new file mode 100644
index 000000000..d3efa9c13
--- /dev/null
+++ b/tools/perf/util/mem-info.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/zalloc.h>
+#include "mem-info.h"
+
+struct mem_info *mem_info__get(struct mem_info *mi)
+{
+	struct mem_info *result;
+
+	if (RC_CHK_GET(result, mi))
+		refcount_inc(mem_info__refcnt(mi));
+
+	return result;
+}
+
+void mem_info__put(struct mem_info *mi)
+{
+	if (mi && refcount_dec_and_test(mem_info__refcnt(mi))) {
+		addr_map_symbol__exit(mem_info__iaddr(mi));
+		addr_map_symbol__exit(mem_info__daddr(mi));
+		RC_CHK_FREE(mi);
+	} else {
+		RC_CHK_PUT(mi);
+	}
+}
+
+struct mem_info *mem_info__new(void)
+{
+	struct mem_info *result = NULL;
+	RC_STRUCT(mem_info) *mi = zalloc(sizeof(*mi));
+
+	if (ADD_RC_CHK(result, mi))
+		refcount_set(mem_info__refcnt(result), 1);
+
+	return result;
+}
+
+struct mem_info *mem_info__clone(struct mem_info *mi)
+{
+	struct mem_info *result = mem_info__new();
+
+	if (result) {
+		addr_map_symbol__copy(mem_info__iaddr(result), mem_info__iaddr(mi));
+		addr_map_symbol__copy(mem_info__daddr(result), mem_info__daddr(mi));
+		mem_info__data_src(result)->val = mem_info__data_src(mi)->val;
+	}
+
+	return result;
+}