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, 53 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-rtrs-server b/Documentation/ABI/testing/sysfs-class-rtrs-server
new file mode 100644
index 000000000..b08601d80
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rtrs-server
@@ -0,0 +1,53 @@
+What:		/sys/class/rtrs-server
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	When a user of RTRS API creates a new session on a client side, a
+		directory entry with the name of that session is created in here.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	When new path is created by writing to "add_path" entry on client side,
+		a directory entry named as <source address>@<destination address> is created
+		on server.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/disconnect
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	When "1" is written to the file, the RTRS session is being disconnected.
+		Operations is non-blocking and returns control immediately to the caller.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/hca_name
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the name of HCA the connection established on.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/hca_port
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the port number of active port traffic is going through.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/src_addr
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the source address of the path
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/dst_addr
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the destination address of the path
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/stats/rdma
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Contains statistics regarding rdma operations and inflight operations.
+		The output consists of 5 values:
+		<read-count> <read-total-size> <write-count> <write-total-size> <inflights>