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, 68 insertions, 0 deletions

diff --git a/scripts/module.lds.S b/scripts/module.lds.S
new file mode 100644
index 000000000..b62683061
--- /dev/null
+++ b/scripts/module.lds.S
@@ -0,0 +1,68 @@
+/*
+ * Common module linker script, always used when linking a module.
+ * Archs are free to supply their own linker scripts.  ld will
+ * combine them automatically.
+ */
+#ifdef CONFIG_UNWIND_TABLES
+#define DISCARD_EH_FRAME
+#else
+#define DISCARD_EH_FRAME	*(.eh_frame)
+#endif
+
+#include <asm-generic/codetag.lds.h>
+
+SECTIONS {
+	/DISCARD/ : {
+		*(.discard)
+		*(.discard.*)
+		*(.export_symbol)
+		*(.no_trim_symbol)
+	}
+
+	__ksymtab		0 : ALIGN(8) { *(SORT(___ksymtab+*)) }
+	__kcrctab		0 : ALIGN(4) { *(SORT(___kcrctab+*)) }
+	__kflagstab		0 : ALIGN(1) { *(SORT(___kflagstab+*)) }
+
+	.ctors			0 : ALIGN(8) { *(SORT(.ctors.*)) *(.ctors) }
+	.init_array		0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) }
+
+	.altinstructions	0 : ALIGN(8) { KEEP(*(.altinstructions)) }
+	__bug_table		0 : ALIGN(8) { KEEP(*(__bug_table)) }
+	__jump_table		0 : ALIGN(8) { KEEP(*(__jump_table)) }
+	__ex_table		0 : ALIGN(4) { KEEP(*(__ex_table)) }
+
+	__patchable_function_entries 0 : { *(__patchable_function_entries) }
+
+	.init.klp_funcs		0 : ALIGN(8) { KEEP(*(.init.klp_funcs)) }
+	.init.klp_objects	0 : ALIGN(8) { KEEP(*(.init.klp_objects)) }
+
+#ifdef CONFIG_ARCH_USES_CFI_TRAPS
+	__kcfi_traps		0 : { KEEP(*(.kcfi_traps)) }
+#endif
+
+#ifndef CONFIG_ARCH_WANTS_MODULES_TEXT_SECTIONS
+	.text			0 : {
+		*(.text .text.[0-9a-zA-Z_]*)
+	}
+#endif
+
+	.bss			0 : {
+		*(.bss .bss.[0-9a-zA-Z_]*)
+		*(.bss..L*)
+	}
+
+	.data			0 : {
+		*(.data .data.[0-9a-zA-Z_]*)
+		*(.data..L*)
+	}
+
+	.rodata			0 : {
+		*(.rodata .rodata.[0-9a-zA-Z_]*)
+		*(.rodata..L*)
+	}
+
+	MOD_SEPARATE_CODETAG_SECTIONS()
+}
+
+/* bring in arch-specific sections */
+#include <asm/module.lds.h>