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, 110 insertions, 0 deletions

diff --git a/scripts/coccinelle/misc/warn.cocci b/scripts/coccinelle/misc/warn.cocci
new file mode 100644
index 000000000..b5f428035
--- /dev/null
+++ b/scripts/coccinelle/misc/warn.cocci
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/// Use WARN(1,...) rather than printk followed by WARN_ON(1)
+///
+// Confidence: High
+// Copyright: (C) 2012 Julia Lawall, INRIA/LIP6.
+// Copyright: (C) 2012 Gilles Muller, INRIA/LiP6.
+// URL: https://coccinelle.gitlabpages.inria.fr/website
+// Comments:
+// Options: --no-includes --include-headers
+
+virtual patch
+virtual context
+virtual org
+virtual report
+
+@bad1@
+position p;
+@@
+
+printk(...);
+printk@p(...);
+WARN_ON(1);
+
+@r1 depends on context || report || org@
+position p != bad1.p;
+@@
+
+ printk@p(...);
+*WARN_ON(1);
+
+@script:python depends on org@
+p << r1.p;
+@@
+
+cocci.print_main("printk + WARN_ON can be just WARN",p)
+
+@script:python depends on report@
+p << r1.p;
+@@
+
+msg = "SUGGESTION: printk + WARN_ON can be just WARN"
+coccilib.report.print_report(p[0],msg)
+
+@ok1 depends on patch@
+expression list es;
+position p != bad1.p;
+@@
+
+-printk@p(
++WARN(1,
+  es);
+-WARN_ON(1);
+
+@depends on patch@
+expression list ok1.es;
+@@
+
+if (...)
+- {
+  WARN(1,es);
+- }
+
+// --------------------------------------------------------------------
+
+@bad2@
+position p;
+@@
+
+printk(...);
+printk@p(...);
+WARN_ON_ONCE(1);
+
+@r2 depends on context || report || org@
+position p != bad1.p;
+@@
+
+ printk@p(...);
+*WARN_ON_ONCE(1);
+
+@script:python depends on org@
+p << r2.p;
+@@
+
+cocci.print_main("printk + WARN_ON_ONCE can be just WARN_ONCE",p)
+
+@script:python depends on report@
+p << r2.p;
+@@
+
+msg = "SUGGESTION: printk + WARN_ON_ONCE can be just WARN_ONCE"
+coccilib.report.print_report(p[0],msg)
+
+@ok2 depends on patch@
+expression list es;
+position p != bad2.p;
+@@
+
+-printk@p(
++WARN_ONCE(1,
+  es);
+-WARN_ON_ONCE(1);
+
+@depends on patch@
+expression list ok2.es;
+@@
+
+if (...)
+- {
+  WARN_ONCE(1,es);
+- }