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, 39 insertions, 0 deletions

diff --git a/drivers/net/plip/Kconfig b/drivers/net/plip/Kconfig
new file mode 100644
index 000000000..67bfb01de
--- /dev/null
+++ b/drivers/net/plip/Kconfig
@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Parallel Line Internet Protocol (PLIP) network device configuration
+#
+
+config PLIP
+	tristate "PLIP (parallel port) support"
+	depends on PARPORT
+	help
+	  PLIP (Parallel Line Internet Protocol) is used to create a
+	  reasonably fast mini network consisting of two (or, rarely, more)
+	  local machines.  A PLIP link from a Linux box is a popular means to
+	  install a Linux distribution on a machine which doesn't have a
+	  CD-ROM drive (a minimal system has to be transferred with floppies
+	  first). The kernels on both machines need to have this PLIP option
+	  enabled for this to work.
+
+	  The PLIP driver has two modes, mode 0 and mode 1.  The parallel
+	  ports (the connectors at the computers with 25 holes) are connected
+	  with "null printer" or "Turbo Laplink" cables which can transmit 4
+	  bits at a time (mode 0) or with special PLIP cables, to be used on
+	  bidirectional parallel ports only, which can transmit 8 bits at a
+	  time (mode 1); you can find the wiring of these cables in
+	  <file:Documentation/networking/plip.rst>.  The cables can be up to
+	  15m long.  Mode 0 works also if one of the machines runs DOS/Windows
+	  and has some PLIP software installed, e.g. the Crynwr PLIP packet
+	  driver (<http://oak.oakland.edu/simtel.net/msdos/pktdrvr-pre.html>)
+	  and winsock or NCSA's telnet.
+
+	  If you want to use PLIP, say Y and read the PLIP mini-HOWTO as well
+	  as the NET-3-HOWTO, both available from
+	  <http://www.tldp.org/docs.html#howto>.  Note that the PLIP
+	  protocol has been changed and this PLIP driver won't work together
+	  with the PLIP support in Linux versions 1.0.x.  This option enlarges
+	  your kernel by about 8 KB.
+
+	  To compile this driver as a module, choose M here. The module
+	  will be called plip. If unsure, say Y or M, in case you buy
+	  a laptop later.