releases/2.6.18.3/make-alignment-exception-always-check-exception-table.patch

   1 From 4393c4f6788cee65095dd838cfeca6edefbfeb52 Mon Sep 17 00:00:00 2001
   2 From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
   3 Message-Id: <1162416427.25682.429.camel@localhost.localdomain>
   4 Date: Wed, 1 Nov 2006 15:11:39 +1100
   5 Subject: POWERPC: Make alignment exception always check exception table
   6
   7 The alignment exception used to only check the exception table for
   8 -EFAULT, not for other errors. That opens an oops window if we can
   9 coerce the kernel into getting an alignment exception for other reasons
  10 in what would normally be a user-protected accessor, which can be done
  11 via some of the futex ops. This fixes it by always checking the
  12 exception tables.
  13
  14 Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
  15 Signed-off-by: Paul Mackerras <paulus@samba.org>
  16 Signed-off-by: Chris Wright <chrisw@sous-sol.org>
  17 ---
  18  arch/powerpc/kernel/traps.c |   18 ++++++++++--------
  19  arch/ppc/kernel/traps.c     |   18 ++++++++++--------
  20  2 files changed, 20 insertions(+), 16 deletions(-)
  21
  22 --- linux-2.6.18.2.orig/arch/powerpc/kernel/traps.c
  23 +++ linux-2.6.18.2/arch/powerpc/kernel/traps.c
  24 @@ -818,7 +818,7 @@ void __kprobes program_check_exception(s
  25
  26  void alignment_exception(struct pt_regs *regs)
  27  {
  28 -       int fixed = 0;
  29 +       int sig, code, fixed = 0;
  30
  31         /* we don't implement logging of alignment exceptions */
  32         if (!(current->thread.align_ctl & PR_UNALIGN_SIGBUS))
  33 @@ -832,14 +832,16 @@ void alignment_exception(struct pt_regs
  34
  35         /* Operand address was bad */
  36         if (fixed == -EFAULT) {
  37 -               if (user_mode(regs))
  38 -                       _exception(SIGSEGV, regs, SEGV_ACCERR, regs->dar);
  39 -               else
  40 -                       /* Search exception table */
  41 -                       bad_page_fault(regs, regs->dar, SIGSEGV);
  42 -               return;
  43 +               sig = SIGSEGV;
  44 +               code = SEGV_ACCERR;
  45 +       } else {
  46 +               sig = SIGBUS;
  47 +               code = BUS_ADRALN;
  48         }
  49 -       _exception(SIGBUS, regs, BUS_ADRALN, regs->dar);
  50 +       if (user_mode(regs))
  51 +               _exception(sig, regs, code, regs->dar);
  52 +       else
  53 +               bad_page_fault(regs, regs->dar, sig);
  54  }
  55
  56  void StackOverflow(struct pt_regs *regs)
  57 --- linux-2.6.18.2.orig/arch/ppc/kernel/traps.c
  58 +++ linux-2.6.18.2/arch/ppc/kernel/traps.c
  59 @@ -708,7 +708,7 @@ void single_step_exception(struct pt_reg
  60
  61  void alignment_exception(struct pt_regs *regs)
  62  {
  63 -       int fixed;
  64 +       int sig, code, fixed = 0;
  65
  66         fixed = fix_alignment(regs);
  67         if (fixed == 1) {
  68 @@ -717,14 +717,16 @@ void alignment_exception(struct pt_regs
  69                 return;
  70         }
  71         if (fixed == -EFAULT) {
  72 -               /* fixed == -EFAULT means the operand address was bad */
  73 -               if (user_mode(regs))
  74 -                       _exception(SIGSEGV, regs, SEGV_ACCERR, regs->dar);
  75 -               else
  76 -                       bad_page_fault(regs, regs->dar, SIGSEGV);
  77 -               return;
  78 +               sig = SIGSEGV;
  79 +               code = SEGV_ACCERR;
  80 +       } else {
  81 +               sig = SIGBUS;
  82 +               code = BUS_ADRALN;
  83         }
  84 -       _exception(SIGBUS, regs, BUS_ADRALN, regs->dar);
  85 +       if (user_mode(regs))
  86 +               _exception(sig, regs, code, regs->dar);
  87 +       else
  88 +               bad_page_fault(regs, regs->dar, sig);
  89  }
  90
  91  void StackOverflow(struct pt_regs *regs)