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, 34 insertions, 0 deletions

diff --git a/fs/jbd2/Kconfig b/fs/jbd2/Kconfig
new file mode 100644
index 000000000..9c19e1512
--- /dev/null
+++ b/fs/jbd2/Kconfig
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config JBD2
+	tristate
+	select CRC32
+	help
+	  This is a generic journaling layer for block devices that support
+	  both 32-bit and 64-bit block numbers.  It is currently used by
+	  the ext4 and OCFS2 filesystems, but it could also be used to add
+	  journal support to other file systems or block devices such
+	  as RAID or LVM.
+
+	  If you are using ext4 or OCFS2, you need to say Y here.
+	  If you are not using ext4 or OCFS2 then you will
+	  probably want to say N.
+
+	  To compile this device as a module, choose M here. The module will be
+	  called jbd2.  If you are compiling ext4 or OCFS2 into the kernel,
+	  you cannot compile this code as a module.
+
+config JBD2_DEBUG
+	bool "JBD2 (ext4) debugging support"
+	depends on JBD2
+	help
+	  If you are using the ext4 journaled file system (or
+	  potentially any other filesystem/device using JBD2), this option
+	  allows you to enable debugging output while the system is running,
+	  in order to help track down any problems you are having.
+	  By default, the debugging output will be turned off.
+
+	  If you select Y here, then you will be able to turn on debugging
+	  with "echo N > /sys/module/jbd2/parameters/jbd2_debug", where N is a
+	  number between 1 and 5. The higher the number, the more debugging
+	  output is generated.  To turn debugging off again, do
+	  "echo 0 > /sys/module/jbd2/parameters/jbd2_debug".