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, 119 insertions, 0 deletions

diff --git a/arch/mips/mm/pgtable-64.c b/arch/mips/mm/pgtable-64.c
new file mode 100644
index 000000000..b24f865de
--- /dev/null
+++ b/arch/mips/mm/pgtable-64.c
@@ -0,0 +1,119 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 1999, 2000 by Silicon Graphics
+ * Copyright (C) 2003 by Ralf Baechle
+ */
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <asm/fixmap.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+
+void pgd_init(void *addr)
+{
+	unsigned long *p, *end;
+	unsigned long entry;
+
+#if !defined(__PAGETABLE_PUD_FOLDED)
+	entry = (unsigned long)invalid_pud_table;
+#elif !defined(__PAGETABLE_PMD_FOLDED)
+	entry = (unsigned long)invalid_pmd_table;
+#else
+	entry = (unsigned long)invalid_pte_table;
+#endif
+
+	p = (unsigned long *) addr;
+	end = p + PTRS_PER_PGD;
+
+	do {
+		p[0] = entry;
+		p[1] = entry;
+		p[2] = entry;
+		p[3] = entry;
+		p[4] = entry;
+		p += 8;
+		p[-3] = entry;
+		p[-2] = entry;
+		p[-1] = entry;
+	} while (p != end);
+}
+
+#ifndef __PAGETABLE_PMD_FOLDED
+void pmd_init(void *addr)
+{
+	unsigned long *p, *end;
+	unsigned long pagetable = (unsigned long)invalid_pte_table;
+
+	p = (unsigned long *)addr;
+	end = p + PTRS_PER_PMD;
+
+	do {
+		p[0] = pagetable;
+		p[1] = pagetable;
+		p[2] = pagetable;
+		p[3] = pagetable;
+		p[4] = pagetable;
+		p += 8;
+		p[-3] = pagetable;
+		p[-2] = pagetable;
+		p[-1] = pagetable;
+	} while (p != end);
+}
+EXPORT_SYMBOL_GPL(pmd_init);
+#endif
+
+#ifndef __PAGETABLE_PUD_FOLDED
+void pud_init(void *addr)
+{
+	unsigned long *p, *end;
+	unsigned long pagetable = (unsigned long)invalid_pmd_table;
+
+	p = (unsigned long *)addr;
+	end = p + PTRS_PER_PUD;
+
+	do {
+		p[0] = pagetable;
+		p[1] = pagetable;
+		p[2] = pagetable;
+		p[3] = pagetable;
+		p[4] = pagetable;
+		p += 8;
+		p[-3] = pagetable;
+		p[-2] = pagetable;
+		p[-1] = pagetable;
+	} while (p != end);
+}
+#endif
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+void set_pmd_at(struct mm_struct *mm, unsigned long addr,
+		pmd_t *pmdp, pmd_t pmd)
+{
+	*pmdp = pmd;
+}
+#endif
+
+void __init pagetable_init(void)
+{
+	unsigned long vaddr;
+	pgd_t *pgd_base;
+
+	/* Initialize the entire pgd.  */
+	pgd_init(swapper_pg_dir);
+#ifndef __PAGETABLE_PUD_FOLDED
+	pud_init(invalid_pud_table);
+#endif
+#ifndef __PAGETABLE_PMD_FOLDED
+	pmd_init(invalid_pmd_table);
+#endif
+	pgd_base = swapper_pg_dir;
+	/*
+	 * Fixed mappings:
+	 */
+	vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
+	fixrange_init(vaddr, vaddr + FIXADDR_SIZE, pgd_base);
+}