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, 15 insertions, 0 deletions

diff --git a/drivers/dma/bestcomm/Makefile b/drivers/dma/bestcomm/Makefile
new file mode 100644
index 000000000..8d1b33a2f
--- /dev/null
+++ b/drivers/dma/bestcomm/Makefile
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for BestComm & co
+#
+
+bestcomm-core-objs	:= bestcomm.o sram.o
+bestcomm-ata-objs	:= ata.o bcom_ata_task.o
+bestcomm-fec-objs	:= fec.o bcom_fec_rx_task.o bcom_fec_tx_task.o
+bestcomm-gen-bd-objs	:= gen_bd.o bcom_gen_bd_rx_task.o bcom_gen_bd_tx_task.o
+
+obj-$(CONFIG_PPC_BESTCOMM)		+= bestcomm-core.o
+obj-$(CONFIG_PPC_BESTCOMM_ATA)		+= bestcomm-ata.o
+obj-$(CONFIG_PPC_BESTCOMM_FEC)		+= bestcomm-fec.o
+obj-$(CONFIG_PPC_BESTCOMM_GEN_BD)	+= bestcomm-gen-bd.o
+