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, 19 insertions, 0 deletions

diff --git a/fs/udf/Kconfig b/fs/udf/Kconfig
new file mode 100644
index 000000000..8f7ce30d4
--- /dev/null
+++ b/fs/udf/Kconfig
@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config UDF_FS
+	tristate "UDF file system support"
+	select BUFFER_HEAD
+	select CRC_ITU_T
+	select NLS
+	select LEGACY_DIRECT_IO
+	help
+	  This is a file system used on some CD-ROMs and DVDs. Since the
+	  file system is supported by multiple operating systems and is more
+	  compatible with standard unix file systems, it is also suitable for
+	  removable USB disks. Say Y if you intend to mount DVD discs or CDRW's
+	  written in packet mode, or if you want to use UDF for removable USB
+	  disks. Please read <file:Documentation/filesystems/udf.rst>.
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called udf.
+
+	  If unsure, say N.