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>

3 files changed, 51 insertions, 0 deletions

diff --git a/tools/testing/selftests/rust/Makefile b/tools/testing/selftests/rust/Makefile
new file mode 100644
index 000000000..fce1584d3
--- /dev/null
+++ b/tools/testing/selftests/rust/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+TEST_PROGS += test_probe_samples.sh
+
+include ../lib.mk
diff --git a/tools/testing/selftests/rust/config b/tools/testing/selftests/rust/config
new file mode 100644
index 000000000..5f942b5c8
--- /dev/null
+++ b/tools/testing/selftests/rust/config
@@ -0,0 +1,6 @@
+# CONFIG_GCC_PLUGINS is not set
+CONFIG_RUST=y
+CONFIG_SAMPLES=y
+CONFIG_SAMPLES_RUST=y
+CONFIG_SAMPLE_RUST_MINIMAL=m
+CONFIG_SAMPLE_RUST_PRINT=m
diff --git a/tools/testing/selftests/rust/test_probe_samples.sh b/tools/testing/selftests/rust/test_probe_samples.sh
new file mode 100755
index 000000000..ad0397e49
--- /dev/null
+++ b/tools/testing/selftests/rust/test_probe_samples.sh
@@ -0,0 +1,41 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (c) 2023 Collabora Ltd
+#
+# This script tests whether the rust sample modules can
+# be added and removed correctly.
+#
+DIR="$(dirname "$(readlink -f "$0")")"
+
+KTAP_HELPERS="${DIR}/../kselftest/ktap_helpers.sh"
+if [ -e "$KTAP_HELPERS" ]; then
+    source "$KTAP_HELPERS"
+else
+    echo "$KTAP_HELPERS file not found [SKIP]"
+    exit 4
+fi
+
+rust_sample_modules=("rust_minimal" "rust_print")
+
+ktap_print_header
+
+for sample in "${rust_sample_modules[@]}"; do
+    if ! /sbin/modprobe -n -q "$sample"; then
+        ktap_skip_all "module $sample is not found in /lib/modules/$(uname -r)"
+        exit "$KSFT_SKIP"
+    fi
+done
+
+ktap_set_plan "${#rust_sample_modules[@]}"
+
+for sample in "${rust_sample_modules[@]}"; do
+    if /sbin/modprobe -q "$sample"; then
+        /sbin/modprobe -q -r "$sample"
+        ktap_test_pass "$sample"
+    else
+        ktap_test_fail "$sample"
+    fi
+done
+
+ktap_finished