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, 46 insertions, 0 deletions

diff --git a/fs/afs/Makefile b/fs/afs/Makefile
new file mode 100644
index 000000000..0d8f1982d
--- /dev/null
+++ b/fs/afs/Makefile
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for Red Hat Linux AFS client.
+#
+
+kafs-y := \
+	addr_list.o \
+	addr_prefs.o \
+	callback.o \
+	cell.o \
+	cm_security.o \
+	cmservice.o \
+	dir.o \
+	dir_edit.o \
+	dir_search.o \
+	dir_silly.o \
+	dynroot.o \
+	file.o \
+	flock.o \
+	fsclient.o \
+	fs_operation.o \
+	fs_probe.o \
+	inode.o \
+	main.o \
+	misc.o \
+	mntpt.o \
+	rotate.o \
+	rxrpc.o \
+	security.o \
+	server.o \
+	server_list.o \
+	super.o \
+	symlink.o \
+	validation.o \
+	vlclient.o \
+	vl_alias.o \
+	vl_list.o \
+	vl_probe.o \
+	vl_rotate.o \
+	volume.o \
+	write.o \
+	xattr.o \
+	yfsclient.o
+
+kafs-$(CONFIG_PROC_FS) += proc.o
+obj-$(CONFIG_AFS_FS)  := kafs.o