1. 29 Nov, 2017 1 commit
    • Tobin C. Harding's avatar
      printk: hash addresses printed with %p · ad67b74d
      Tobin C. Harding authored
      Currently there exist approximately 14 000 places in the kernel where
      addresses are being printed using an unadorned %p. This potentially
      leaks sensitive information regarding the Kernel layout in memory. Many
      of these calls are stale, instead of fixing every call lets hash the
      address by default before printing. This will of course break some
      users, forcing code printing needed addresses to be updated.
      Code that _really_ needs the address will soon be able to use the new
      printk specifier %px to print the address.
      For what it's worth, usage of unadorned %p can be broken down as
      follows (thanks to Joe Perches).
      $ git grep -E '%p[^A-Za-z0-9]' | cut -f1 -d"/" | sort | uniq -c
         1084 arch
           20 block
           10 crypto
           32 Documentation
         8121 drivers
         1221 fs
          143 include
          101 kernel
           69 lib
          100 mm
         1510 net
           40 samples
            7 scripts
           11 security
          166 sound
          152 tools
            2 virt
      Add function ptr_to_id() to map an address to a 32 bit unique
      identifier. Hash any unadorned usage of specifier %p and any malformed
      Signed-off-by: 's avatarTobin C. Harding <me@tobin.cc>
  2. 15 Mar, 2016 1 commit
    • Vlastimil Babka's avatar
      mm, printk: introduce new format string for flags · edf14cdb
      Vlastimil Babka authored
      In mm we use several kinds of flags bitfields that are sometimes printed
      for debugging purposes, or exported to userspace via sysfs.  To make
      them easier to interpret independently on kernel version and config, we
      want to dump also the symbolic flag names.  So far this has been done
      with repeated calls to pr_cont(), which is unreliable on SMP, and not
      usable for e.g.  sysfs export.
      To get a more reliable and universal solution, this patch extends
      printk() format string for pointers to handle the page flags (%pGp),
      gfp_flags (%pGg) and vma flags (%pGv).  Existing users of
      dump_flag_names() are converted and simplified.
      It would be possible to pass flags by value instead of pointer, but the
      %p format string for pointers already has extensions for various kernel
      structures, so it's a good fit, and the extra indirection in a
      non-critical path is negligible.
      [linux@rasmusvillemoes.dk: lots of good implementation suggestions]
      Signed-off-by: 's avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: 's avatarMichal Hocko <mhocko@suse.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Sasha Levin <sasha.levin@oracle.com>
      Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
  3. 16 Jan, 2016 7 commits
  4. 07 Nov, 2015 1 commit
    • Rasmus Villemoes's avatar
      test_printf: test printf family at runtime · 707cc728
      Rasmus Villemoes authored
      This adds a simple module for testing the kernel's printf facilities.
      Previously, some %p extensions have caused a wrong return value in case
      the entire output didn't fit and/or been unusable in kasprintf().  This
      should help catch such issues.  Also, it should help ensure that changes
      to the formatting algorithms don't break anything.
      I'm not sure if we have a struct dentry or struct file lying around at
      boot time or if we can fake one, but most %p extensions should be
      testable, as should the ordinary number and string formatting.
      The nature of vararg functions means we can't use a more conventional
      table-driven approach.
      For now, this is mostly a skeleton; contributions are very
      welcome. Some tests are/will be slightly annoying to write, since the
      expected output depends on stuff like CONFIG_*, sizeof(long), runtime
      values etc.
      Signed-off-by: 's avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
      Reviewed-by: 's avatarKees Cook <keescook@chromium.org>
      Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
      Cc: Martin Kletzander <mkletzan@redhat.com>
      Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>