avr32: Fix oops on unaligned user access

The unaligned address exception handler (and others) does not scan the
fixup tables before oopsing. This is bad because it means passing a
badly aligned pointer from user space might crash the kernel.

Fix this by scanning the fixup tables in _exception(). This should
resolve the issue for unaligned addresses as well as other less common
exceptions that might be happening during a userspace access. The page
fault handler already does fixup processing.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/arch/avr32/kernel/traps.c b/arch/avr32/kernel/traps.c
index d547c8df157d..6e3d491184ea 100644
--- a/arch/avr32/kernel/traps.c
+++ b/arch/avr32/kernel/traps.c
@@ -75,8 +75,17 @@ void _exception(long signr, struct pt_regs *regs, int code,
 {
         siginfo_t info;
 
-        if (!user_mode(regs))
+        if (!user_mode(regs)) {
+                const struct exception_table_entry *fixup;
+
+                /* Are we prepared to handle this kernel fault? */
+                fixup = search_exception_tables(regs->pc);
+                if (fixup) {
+                        regs->pc = fixup->fixup;
+                        return;
+                }
                 die("Unhandled exception in kernel mode", regs, signr);
+        }
 
         memset(&info, 0, sizeof(info));
         info.si_signo = signr;