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, 14 insertions, 0 deletions

diff --git a/fs/coda/Makefile b/fs/coda/Makefile
new file mode 100644
index 000000000..78befb836
--- /dev/null
+++ b/fs/coda/Makefile
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the Linux Coda filesystem routines.
+#
+
+obj-$(CONFIG_CODA_FS) += coda.o
+
+coda-objs := psdev.o cache.o cnode.o inode.o dir.o file.o upcall.o \
+	     coda_linux.o symlink.o pioctl.o
+coda-$(CONFIG_SYSCTL) += sysctl.o
+
+# If you want debugging output, please uncomment the following line.
+
+# ccflags-y := -DDEBUG -DDEBUG_SMB_MALLOC=1