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, 45 insertions, 0 deletions

diff --git a/arch/m68k/Kconfig.debug b/arch/m68k/Kconfig.debug
new file mode 100644
index 000000000..d036f9038
--- /dev/null
+++ b/arch/m68k/Kconfig.debug
@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config BOOTPARAM
+	bool "Compiled-in Kernel Boot Parameter"
+
+config BOOTPARAM_STRING
+	string "Kernel Boot Parameter"
+	default "console=ttyS0,19200"
+	depends on BOOTPARAM
+
+config EARLY_PRINTK
+	bool "Early printk"
+	depends on MMU_MOTOROLA
+	help
+	  Write kernel log output directly to a serial port.
+	  Where implemented, output goes to the framebuffer as well.
+	  PROM console functionality on Sun 3x is not affected by this option.
+
+	  Pass "earlyprintk" on the kernel command line to get a
+	  boot console.
+
+	  This is useful for kernel debugging when your machine crashes very
+	  early, i.e. before the normal console driver is loaded.
+	  You should normally say N here, unless you want to debug such a crash.
+
+if !MMU
+
+config FULLDEBUG
+	bool "Full Symbolic/Source Debugging support"
+	help
+	  Enable debugging symbols on kernel build.
+
+config HIGHPROFILE
+	bool "Use fast second timer for profiling"
+	depends on COLDFIRE
+	help
+	  Use a fast secondary clock to produce profiling information.
+
+config BDM_DISABLE
+	bool "Disable BDM signals"
+	depends on COLDFIRE
+	help
+	  Disable the ColdFire CPU's BDM signals.
+
+endif