src/patches/suse-2.6.27.31/patches.arch/compat-sys-swapcontext

   1 From: schwab@suse.de
   2 Subject: Fix msr check in compat_sys_swapcontext
   3 References: 441498
   4
   5 The new context may not be 16-byte aligned, so the real address of the
   6 mcontext structure should be read from the uc_regs pointer instead of
   7 directly using the (unaligned) uc_mcontext field.
   8
   9 Signed-off-by: Andreas Schwab <schwab@suse.de>
  10
  11 ---
  12 ---
  13  arch/powerpc/kernel/signal_32.c |   14 +++++++++++---
  14  1 file changed, 11 insertions(+), 3 deletions(-)
  15
  16 --- a/arch/powerpc/kernel/signal_32.c
  17 +++ b/arch/powerpc/kernel/signal_32.c
  18 @@ -941,9 +941,17 @@ long sys_swapcontext(struct ucontext __u
  19  #ifdef CONFIG_PPC64
  20         unsigned long new_msr = 0;
  21
  22 -       if (new_ctx &&
  23 -           get_user(new_msr, &new_ctx->uc_mcontext.mc_gregs[PT_MSR]))
  24 -               return -EFAULT;
  25 +       if (new_ctx) {
  26 +               struct mcontext __user *mcp;
  27 +               u32 cmcp;
  28 +
  29 +               /* Get pointer to the real mcontext. */
  30 +               if (get_user(cmcp, &new_ctx->uc_regs))
  31 +                       return -EFAULT;
  32 +               mcp = (struct mcontext __user *)(u64)cmcp;
  33 +               if (get_user(new_msr, &mcp->mc_gregs[PT_MSR]))
  34 +                       return -EFAULT;
  35 +       }
  36         /*
  37          * Check that the context is not smaller than the original
  38          * size (with VMX but without VSX)