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, 37 insertions, 0 deletions

diff --git a/net/atm/Kconfig b/net/atm/Kconfig
new file mode 100644
index 000000000..dfdc3a855
--- /dev/null
+++ b/net/atm/Kconfig
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Asynchronous Transfer Mode (ATM)
+#
+
+config ATM
+	tristate "Asynchronous Transfer Mode (ATM)"
+	help
+	  ATM is a high-speed networking technology for Local Area Networks
+	  and Wide Area Networks.  It uses a fixed packet size and is
+	  connection oriented, allowing for the negotiation of minimum
+	  bandwidth requirements.
+
+	  In order to participate in an ATM network, your Linux box needs an
+	  ATM networking card. If you have that, say Y here and to the driver
+	  of your ATM card below.
+
+	  Note that you need a set of user-space programs to actually make use
+	  of ATM.  See the file <file:Documentation/networking/atm.rst> for
+	  further details.
+
+config ATM_BR2684
+	tristate "RFC1483/2684 Bridged protocols"
+	depends on ATM && INET
+	help
+	  ATM PVCs can carry ethernet PDUs according to RFC2684 (formerly 1483)
+	  This device will act like an ethernet from the kernels point of view,
+	  with the traffic being carried by ATM PVCs (currently 1 PVC/device).
+	  This is sometimes used over DSL lines.  If in doubt, say N.
+
+config ATM_BR2684_IPFILTER
+	bool "Per-VC IP filter kludge"
+	depends on ATM_BR2684
+	help
+	  This is an experimental mechanism for users who need to terminate a
+	  large number of IP-only vcc's.  Do not enable this unless you are sure
+	  you know what you are doing.