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, 32 insertions, 0 deletions

diff --git a/drivers/video/logo/Makefile b/drivers/video/logo/Makefile
new file mode 100644
index 000000000..937b37d3b
--- /dev/null
+++ b/drivers/video/logo/Makefile
@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for the Linux logos
+
+obj-$(CONFIG_LOGO)			+= logo.o
+obj-$(CONFIG_LOGO_LINUX_MONO)		+= logo_linux_mono.o
+obj-$(CONFIG_LOGO_LINUX_VGA16)		+= logo_linux_vga16.o
+obj-$(CONFIG_LOGO_LINUX_CLUT224)	+= logo_linux_clut224.o
+
+obj-$(CONFIG_SPU_BASE)			+= logo_spe_clut224.o
+
+# How to generate logo's
+
+hostprogs := pnmtologo
+
+# Create commands like "pnmtologo -t mono -n logo_linux_mono -o ..."
+quiet_cmd_logo = LOGO    $@
+      cmd_logo = $(obj)/pnmtologo -t $2 -n $(basename $(notdir $@)) -o $@ $<
+
+$(obj)/logo_linux_mono.c: $(CONFIG_LOGO_LINUX_MONO_FILE) $(obj)/pnmtologo FORCE
+	$(call if_changed,logo,mono)
+
+$(obj)/logo_linux_vga16.c: $(CONFIG_LOGO_LINUX_VGA16_FILE) $(obj)/pnmtologo FORCE
+	$(call if_changed,logo,vga16)
+
+$(obj)/logo_linux_clut224.c: $(CONFIG_LOGO_LINUX_CLUT224_FILE) $(obj)/pnmtologo FORCE
+	$(call if_changed,logo,clut224)
+
+$(obj)/%_clut224.c: $(src)/%_clut224.ppm $(obj)/pnmtologo FORCE
+	$(call if_changed,logo,clut224)
+
+# generated C files
+targets += *_mono.c *_vga16.c *_clut224.c