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, 29 insertions, 0 deletions

diff --git a/drivers/block/rnbd/Kconfig b/drivers/block/rnbd/Kconfig
new file mode 100644
index 000000000..2ff05a0d2
--- /dev/null
+++ b/drivers/block/rnbd/Kconfig
@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+config BLK_DEV_RNBD
+	bool
+
+config BLK_DEV_RNBD_CLIENT
+	tristate "RDMA Network Block Device driver client"
+	depends on INFINIBAND_RTRS_CLIENT
+	select BLK_DEV_RNBD
+	select SG_POOL
+	help
+	  RNBD client is a network block device driver using rdma transport.
+
+	  RNBD client allows for mapping of a remote block devices over
+	  RTRS protocol from a target system where RNBD server is running.
+
+	  If unsure, say N.
+
+config BLK_DEV_RNBD_SERVER
+	tristate "RDMA Network Block Device driver server"
+	depends on INFINIBAND_RTRS_SERVER
+	select BLK_DEV_RNBD
+	help
+	  RNBD server is the server side of RNBD using rdma transport.
+
+	  RNBD server allows for exporting local block devices to a remote client
+	  over RTRS protocol.
+
+	  If unsure, say N.