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, 31 insertions, 0 deletions

diff --git a/drivers/media/common/Kconfig b/drivers/media/common/Kconfig
new file mode 100644
index 000000000..adcb66553
--- /dev/null
+++ b/drivers/media/common/Kconfig
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Used by common drivers, when they need to ask questions
+config MEDIA_COMMON_OPTIONS
+	bool
+
+comment "common driver options"
+	depends on MEDIA_COMMON_OPTIONS
+
+config CYPRESS_FIRMWARE
+	tristate
+	depends on USB
+
+config TTPCI_EEPROM
+        tristate
+        depends on I2C
+
+config UVC_COMMON
+	tristate
+
+config VIDEO_CX2341X
+	tristate
+
+config VIDEO_TVEEPROM
+	tristate
+	depends on I2C
+
+source "drivers/media/common/b2c2/Kconfig"
+source "drivers/media/common/saa7146/Kconfig"
+source "drivers/media/common/siano/Kconfig"
+source "drivers/media/common/v4l2-tpg/Kconfig"
+source "drivers/media/common/videobuf2/Kconfig"