queue-4.4/binfmt_elf-switch-to-new-creds-when-switching-to-new-mm.patch

   1 From 9f834ec18defc369d73ccf9e87a2790bfa05bf46 Mon Sep 17 00:00:00 2001
   2 From: Linus Torvalds <torvalds@linux-foundation.org>
   3 Date: Mon, 22 Aug 2016 16:41:46 -0700
   4 Subject: binfmt_elf: switch to new creds when switching to new mm
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 From: Linus Torvalds <torvalds@linux-foundation.org>
  10
  11 commit 9f834ec18defc369d73ccf9e87a2790bfa05bf46 upstream.
  12
  13 We used to delay switching to the new credentials until after we had
  14 mapped the executable (and possible elf interpreter).  That was kind of
  15 odd to begin with, since the new executable will actually then _run_
  16 with the new creds, but whatever.
  17
  18 The bigger problem was that we also want to make sure that we turn off
  19 prof events and tracing before we start mapping the new executable
  20 state.  So while this is a cleanup, it's also a fix for a possible
  21 information leak.
  22
  23 Reported-by: Robert Święcki <robert@swiecki.net>
  24 Tested-by: Peter Zijlstra <peterz@infradead.org>
  25 Acked-by: David Howells <dhowells@redhat.com>
  26 Acked-by: Oleg Nesterov <oleg@redhat.com>
  27 Acked-by: Andy Lutomirski <luto@amacapital.net>
  28 Acked-by: Eric W. Biederman <ebiederm@xmission.com>
  29 Cc: Willy Tarreau <w@1wt.eu>
  30 Cc: Kees Cook <keescook@chromium.org>
  31 Cc: Al Viro <viro@zeniv.linux.org.uk>
  32 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  33 Cc: Federico Manuel Bento <up201407890@fc.up.pt>
  34 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  35
  36 ---
  37  fs/binfmt_elf.c |    2 +-
  38  1 file changed, 1 insertion(+), 1 deletion(-)
  39
  40 --- a/fs/binfmt_elf.c
  41 +++ b/fs/binfmt_elf.c
  42 @@ -850,6 +850,7 @@ static int load_elf_binary(struct linux_
  43                 current->flags |= PF_RANDOMIZE;
  44
  45         setup_new_exec(bprm);
  46 +       install_exec_creds(bprm);
  47
  48         /* Do this so that we can load the interpreter, if need be.  We will
  49            change some of these later */
  50 @@ -1084,7 +1085,6 @@ static int load_elf_binary(struct linux_
  51                 goto out;
  52  #endif /* ARCH_HAS_SETUP_ADDITIONAL_PAGES */
  53
  54 -       install_exec_creds(bprm);
  55         retval = create_elf_tables(bprm, &loc->elf_ex,
  56                           load_addr, interp_load_addr);
  57         if (retval < 0)