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To: Ralf Baechle <ralf@oss.sgi.com>
Cc: linux-mips@oss.sgi.com
Subject: Fixup in unaligned.c
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It seems we don't always handle bad user-mode pointers correctly.
If put_user is called with an unmapped AND unaligned address it
kills the current process instead of returning EFAULT.

The reason for this is that we do compute_return_epc() in do_ade()
before the exception table is searched, so we never get a match.

Below is a simple patch to fix it (attached as well).
The second part is not related, but it makes sense to only consult
the MF_FIXADE flag on exceptions originating from user-mode, right?

-Tommy


--- arch/mips/kernel/unaligned.c        2001/10/05 15:13:25     1.14
+++ arch/mips/kernel/unaligned.c        2001/10/29 12:39:56
@@ -353,12 +353,12 @@

 fault:
        /* Did we have an exception handler installed? */
-       fixup = search_exception_table(regs->cp0_epc);
+       fixup = search_exception_table(pc);
        if (fixup) {
                long new_epc;
-               new_epc = fixup_exception(dpf_reg, fixup, regs->cp0_epc);
+               new_epc = fixup_exception(dpf_reg, fixup, pc);
                printk(KERN_DEBUG "%s: Forwarding exception at [<%lx>]
(%lx)\n",
-                      current->comm, regs->cp0_epc, new_epc);
+                      current->comm, pc, new_epc);
                regs->cp0_epc = new_epc;
                return;
        }
@@ -408,7 +408,7 @@
        pc = regs->cp0_epc + ((regs->cp0_cause & CAUSEF_BD) ? 4 : 0);
        if (compute_return_epc(regs))
                return;
-       if ((current->thread.mflags & MF_FIXADE) == 0)
+       if (user_mode(regs) && (current->thread.mflags & MF_FIXADE) == 0)
                goto sigbus;

        emulate_load_store_insn(regs, regs->cp0_badvaddr, pc);
(See attached file: unaligned.c.patch.gz)
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