releases/3.4.16/amd64_edac-__amd64_set_scrub_rate-avoid-overindexing-scrubrates.patch

   1 From 168bfeef7bba3f9784f7540b053e4ac72b769ce9 Mon Sep 17 00:00:00 2001
   2 From: Andrew Morton <akpm@linux-foundation.org>
   3 Date: Tue, 23 Oct 2012 14:09:39 -0700
   4 Subject: amd64_edac:__amd64_set_scrub_rate(): avoid overindexing scrubrates[]
   5
   6 From: Andrew Morton <akpm@linux-foundation.org>
   7
   8 commit 168bfeef7bba3f9784f7540b053e4ac72b769ce9 upstream.
   9
  10 If none of the elements in scrubrates[] matches, this loop will cause
  11 __amd64_set_scrub_rate() to incorrectly use the n+1th element.
  12
  13 As the function is designed to use the final scrubrates[] element in the
  14 case of no match, we can fix this bug by simply terminating the array
  15 search at the n-1th element.
  16
  17 Boris: this code is fragile anyway, see here why:
  18 http://marc.info/?l=linux-kernel&m=135102834131236&w=2
  19
  20 It will be rewritten more robustly soonish.
  21
  22 Reported-by: Denis Kirjanov <kirjanov@gmail.com>
  23 Cc: Doug Thompson <dougthompson@xmission.com>
  24 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  25 Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
  26 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  27
  28 ---
  29  drivers/edac/amd64_edac.c |   11 ++++-------
  30  1 file changed, 4 insertions(+), 7 deletions(-)
  31
  32 --- a/drivers/edac/amd64_edac.c
  33 +++ b/drivers/edac/amd64_edac.c
  34 @@ -170,8 +170,11 @@ static int __amd64_set_scrub_rate(struct
  35          * memory controller and apply to register. Search for the first
  36          * bandwidth entry that is greater or equal than the setting requested
  37          * and program that. If at last entry, turn off DRAM scrubbing.
  38 +        *
  39 +        * If no suitable bandwidth is found, turn off DRAM scrubbing entirely
  40 +        * by falling back to the last element in scrubrates[].
  41          */
  42 -       for (i = 0; i < ARRAY_SIZE(scrubrates); i++) {
  43 +       for (i = 0; i < ARRAY_SIZE(scrubrates) - 1; i++) {
  44                 /*
  45                  * skip scrub rates which aren't recommended
  46                  * (see F10 BKDG, F3x58)
  47 @@ -181,12 +184,6 @@ static int __amd64_set_scrub_rate(struct
  48
  49                 if (scrubrates[i].bandwidth <= new_bw)
  50                         break;
  51 -
  52 -               /*
  53 -                * if no suitable bandwidth found, turn off DRAM scrubbing
  54 -                * entirely by falling back to the last element in the
  55 -                * scrubrates array.
  56 -                */
  57         }
  58
  59         scrubval = scrubrates[i].scrubval;