releases/4.4.61/mm-mempolicy.c-fix-error-handling-in-set_mempolicy-and-mbind.patch

   1 From cf01fb9985e8deb25ccf0ea54d916b8871ae0e62 Mon Sep 17 00:00:00 2001
   2 From: Chris Salls <salls@cs.ucsb.edu>
   3 Date: Fri, 7 Apr 2017 23:48:11 -0700
   4 Subject: mm/mempolicy.c: fix error handling in set_mempolicy and mbind.
   5
   6 From: Chris Salls <salls@cs.ucsb.edu>
   7
   8 commit cf01fb9985e8deb25ccf0ea54d916b8871ae0e62 upstream.
   9
  10 In the case that compat_get_bitmap fails we do not want to copy the
  11 bitmap to the user as it will contain uninitialized stack data and leak
  12 sensitive data.
  13
  14 Signed-off-by: Chris Salls <salls@cs.ucsb.edu>
  15 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  16 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  17
  18 ---
  19  mm/mempolicy.c |   20 ++++++++------------
  20  1 file changed, 8 insertions(+), 12 deletions(-)
  21
  22 --- a/mm/mempolicy.c
  23 +++ b/mm/mempolicy.c
  24 @@ -1492,7 +1492,6 @@ COMPAT_SYSCALL_DEFINE5(get_mempolicy, in
  25  COMPAT_SYSCALL_DEFINE3(set_mempolicy, int, mode, compat_ulong_t __user *, nmask,
  26                        compat_ulong_t, maxnode)
  27  {
  28 -       long err = 0;
  29         unsigned long __user *nm = NULL;
  30         unsigned long nr_bits, alloc_size;
  31         DECLARE_BITMAP(bm, MAX_NUMNODES);
  32 @@ -1501,14 +1500,13 @@ COMPAT_SYSCALL_DEFINE3(set_mempolicy, in
  33         alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
  34
  35         if (nmask) {
  36 -               err = compat_get_bitmap(bm, nmask, nr_bits);
  37 +               if (compat_get_bitmap(bm, nmask, nr_bits))
  38 +                       return -EFAULT;
  39                 nm = compat_alloc_user_space(alloc_size);
  40 -               err |= copy_to_user(nm, bm, alloc_size);
  41 +               if (copy_to_user(nm, bm, alloc_size))
  42 +                       return -EFAULT;
  43         }
  44
  45 -       if (err)
  46 -               return -EFAULT;
  47 -
  48         return sys_set_mempolicy(mode, nm, nr_bits+1);
  49  }
  50
  51 @@ -1516,7 +1514,6 @@ COMPAT_SYSCALL_DEFINE6(mbind, compat_ulo
  52                        compat_ulong_t, mode, compat_ulong_t __user *, nmask,
  53                        compat_ulong_t, maxnode, compat_ulong_t, flags)
  54  {
  55 -       long err = 0;
  56         unsigned long __user *nm = NULL;
  57         unsigned long nr_bits, alloc_size;
  58         nodemask_t bm;
  59 @@ -1525,14 +1522,13 @@ COMPAT_SYSCALL_DEFINE6(mbind, compat_ulo
  60         alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
  61
  62         if (nmask) {
  63 -               err = compat_get_bitmap(nodes_addr(bm), nmask, nr_bits);
  64 +               if (compat_get_bitmap(nodes_addr(bm), nmask, nr_bits))
  65 +                       return -EFAULT;
  66                 nm = compat_alloc_user_space(alloc_size);
  67 -               err |= copy_to_user(nm, nodes_addr(bm), alloc_size);
  68 +               if (copy_to_user(nm, nodes_addr(bm), alloc_size))
  69 +                       return -EFAULT;
  70         }
  71
  72 -       if (err)
  73 -               return -EFAULT;
  74 -
  75         return sys_mbind(start, len, mode, nm, nr_bits+1, flags);
  76  }
  77