releases/3.0.49/kernel-sys.c-fix-stack-memory-content-leak-via-uname26.patch

   1 From 2702b1526c7278c4d65d78de209a465d4de2885e Mon Sep 17 00:00:00 2001
   2 From: Kees Cook <keescook@chromium.org>
   3 Date: Fri, 19 Oct 2012 13:56:51 -0700
   4 Subject: kernel/sys.c: fix stack memory content leak via UNAME26
   5
   6 From: Kees Cook <keescook@chromium.org>
   7
   8 commit 2702b1526c7278c4d65d78de209a465d4de2885e upstream.
   9
  10 Calling uname() with the UNAME26 personality set allows a leak of kernel
  11 stack contents.  This fixes it by defensively calculating the length of
  12 copy_to_user() call, making the len argument unsigned, and initializing
  13 the stack buffer to zero (now technically unneeded, but hey, overkill).
  14
  15 CVE-2012-0957
  16
  17 Reported-by: PaX Team <pageexec@freemail.hu>
  18 Signed-off-by: Kees Cook <keescook@chromium.org>
  19 Cc: Andi Kleen <ak@linux.intel.com>
  20 Cc: PaX Team <pageexec@freemail.hu>
  21 Cc: Brad Spengler <spender@grsecurity.net>
  22 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  23 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  24 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  25
  26 ---
  27  kernel/sys.c |   12 +++++++-----
  28  1 file changed, 7 insertions(+), 5 deletions(-)
  29
  30 --- a/kernel/sys.c
  31 +++ b/kernel/sys.c
  32 @@ -1133,15 +1133,16 @@ DECLARE_RWSEM(uts_sem);
  33   * Work around broken programs that cannot handle "Linux 3.0".
  34   * Instead we map 3.x to 2.6.40+x, so e.g. 3.0 would be 2.6.40
  35   */
  36 -static int override_release(char __user *release, int len)
  37 +static int override_release(char __user *release, size_t len)
  38  {
  39         int ret = 0;
  40 -       char buf[65];
  41
  42         if (current->personality & UNAME26) {
  43 -               char *rest = UTS_RELEASE;
  44 +               const char *rest = UTS_RELEASE;
  45 +               char buf[65] = { 0 };
  46                 int ndots = 0;
  47                 unsigned v;
  48 +               size_t copy;
  49
  50                 while (*rest) {
  51                         if (*rest == '.' && ++ndots >= 3)
  52 @@ -1151,8 +1152,9 @@ static int override_release(char __user
  53                         rest++;
  54                 }
  55                 v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;
  56 -               snprintf(buf, len, "2.6.%u%s", v, rest);
  57 -               ret = copy_to_user(release, buf, len);
  58 +               copy = min(sizeof(buf), max_t(size_t, 1, len));
  59 +               copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
  60 +               ret = copy_to_user(release, buf, copy + 1);
  61         }
  62         return ret;
  63  }