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, 69 insertions, 0 deletions

diff --git a/tools/testing/memblock/internal.h b/tools/testing/memblock/internal.h
new file mode 100644
index 000000000..b6b1d147f
--- /dev/null
+++ b/tools/testing/memblock/internal.h
@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _MM_INTERNAL_H
+#define _MM_INTERNAL_H
+
+/*
+ * Enable memblock_dbg() messages
+ */
+#ifdef MEMBLOCK_DEBUG
+static int memblock_debug = 1;
+#endif
+
+#define pr_warn_ratelimited(fmt, ...)    printf(fmt, ##__VA_ARGS__)
+
+#define K(x) ((x) << (PAGE_SHIFT-10))
+
+bool mirrored_kernelcore = false;
+
+struct page {};
+static inline void *page_address(struct page *page)
+{
+	BUG();
+	return page;
+}
+
+static inline struct page *virt_to_page(void *virt)
+{
+	BUG();
+	return virt;
+}
+
+void memblock_free_pages(unsigned long pfn, unsigned int order)
+{
+}
+
+static inline void accept_memory(phys_addr_t start, unsigned long size)
+{
+}
+
+unsigned long free_reserved_area(void *start, void *end, int poison, const char *s);
+void free_reserved_page(struct page *page);
+
+static inline bool deferred_pages_enabled(void)
+{
+	return false;
+}
+
+#define for_each_valid_pfn(pfn, start_pfn, end_pfn)			 \
+	for ((pfn) = (start_pfn); (pfn) < (end_pfn); (pfn)++)
+
+static inline void *kasan_reset_tag(const void *addr)
+{
+	return (void *)addr;
+}
+
+static inline bool __is_kernel(unsigned long addr)
+{
+	return false;
+}
+
+#define for_each_valid_pfn(pfn, start_pfn, end_pfn)                     \
+       for ((pfn) = (start_pfn); (pfn) < (end_pfn); (pfn)++)
+
+static inline void init_deferred_page(unsigned long pfn, int nid)
+{
+}
+
+#define __SetPageReserved(p)	((void)(p))
+
+#endif