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, 36 insertions, 0 deletions

diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
new file mode 100644
index 000000000..650e804d0
--- /dev/null
+++ b/tools/perf/util/smt.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <string.h>
+#include "api/fs/fs.h"
+#include "cputopo.h"
+#include "smt.h"
+
+bool smt_on(void)
+{
+	static bool cached;
+	static bool cached_result;
+	int fs_value;
+
+	if (cached)
+		return cached_result;
+
+	if (sysfs__read_int("devices/system/cpu/smt/active", &fs_value) >= 0)
+		cached_result = (fs_value == 1);
+	else
+		cached_result = cpu_topology__smt_on(online_topology());
+
+	cached = true;
+	return cached_result;
+}
+
+bool core_wide(bool system_wide, const char *user_requested_cpu_list)
+{
+	/* If not everything running on a core is being recorded then we can't use core_wide. */
+	if (!system_wide)
+		return false;
+
+	/* Cheap case that SMT is disabled and therefore we're inherently core_wide. */
+	if (!smt_on())
+		return true;
+
+	return cpu_topology__core_wide(online_topology(), user_requested_cpu_list);
+}