releases/3.16.3/mips-octeon-make-get_system_type-thread-safe.patch

   1 From 608308682addfdc7b8e2aee88f0e028331d88e4d Mon Sep 17 00:00:00 2001
   2 From: Aaro Koskinen <aaro.koskinen@nsn.com>
   3 Date: Tue, 22 Jul 2014 14:51:08 +0300
   4 Subject: MIPS: OCTEON: make get_system_type() thread-safe
   5
   6 From: Aaro Koskinen <aaro.koskinen@nsn.com>
   7
   8 commit 608308682addfdc7b8e2aee88f0e028331d88e4d upstream.
   9
  10 get_system_type() is not thread-safe on OCTEON. It uses static data,
  11 also more dangerous issue is that it's calling cvmx_fuse_read_byte()
  12 every time without any synchronization. Currently it's possible to get
  13 processes stuck looping forever in kernel simply by launching multiple
  14 readers of /proc/cpuinfo:
  15
  16         (while true; do cat /proc/cpuinfo > /dev/null; done) &
  17         (while true; do cat /proc/cpuinfo > /dev/null; done) &
  18         ...
  19
  20 Fix by initializing the system type string only once during the early
  21 boot.
  22
  23 Signed-off-by: Aaro Koskinen <aaro.koskinen@nsn.com>
  24 Reviewed-by: Markos Chandras <markos.chandras@imgtec.com>
  25 Patchwork: http://patchwork.linux-mips.org/patch/7437/
  26 Signed-off-by: James Hogan <james.hogan@imgtec.com>
  27 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  28
  29 ---
  30  arch/mips/cavium-octeon/setup.c |   18 +++++++++++++-----
  31  1 file changed, 13 insertions(+), 5 deletions(-)
  32
  33 --- a/arch/mips/cavium-octeon/setup.c
  34 +++ b/arch/mips/cavium-octeon/setup.c
  35 @@ -458,6 +458,18 @@ static void octeon_halt(void)
  36         octeon_kill_core(NULL);
  37  }
  38
  39 +static char __read_mostly octeon_system_type[80];
  40 +
  41 +static int __init init_octeon_system_type(void)
  42 +{
  43 +       snprintf(octeon_system_type, sizeof(octeon_system_type), "%s (%s)",
  44 +               cvmx_board_type_to_string(octeon_bootinfo->board_type),
  45 +               octeon_model_get_string(read_c0_prid()));
  46 +
  47 +       return 0;
  48 +}
  49 +early_initcall(init_octeon_system_type);
  50 +
  51  /**
  52   * Return a string representing the system type
  53   *
  54 @@ -465,11 +477,7 @@ static void octeon_halt(void)
  55   */
  56  const char *octeon_board_type_string(void)
  57  {
  58 -       static char name[80];
  59 -       sprintf(name, "%s (%s)",
  60 -               cvmx_board_type_to_string(octeon_bootinfo->board_type),
  61 -               octeon_model_get_string(read_c0_prid()));
  62 -       return name;
  63 +       return octeon_system_type;
  64  }
  65
  66  const char *get_system_type(void)