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, 16 insertions, 0 deletions

diff --git a/fs/unicode/Kconfig b/fs/unicode/Kconfig
new file mode 100644
index 000000000..4ad2c3655
--- /dev/null
+++ b/fs/unicode/Kconfig
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# UTF-8 normalization
+#
+config UNICODE
+	tristate "UTF-8 normalization and casefolding support"
+	help
+	  Say Y here to enable UTF-8 NFD normalization and NFD+CF casefolding
+	  support.  If you say M here the large table of case foldings will
+	  be a separate loadable module that gets requested only when a file
+	  system actually use it.
+
+config UNICODE_NORMALIZATION_KUNIT_TEST
+	tristate "Test UTF-8 normalization support"
+	depends on UNICODE && KUNIT
+	default KUNIT_ALL_TESTS