releases/4.19.34/bcache-fix-potential-div-zero-error-of-writeback_rat.patch-8658

   1 From c27dd0ea1de0607c0b6eaf01e91749f7eb89dae0 Mon Sep 17 00:00:00 2001
   2 From: Coly Li <colyli@suse.de>
   3 Date: Sat, 9 Feb 2019 12:53:06 +0800
   4 Subject: bcache: fix potential div-zero error of writeback_rate_p_term_inverse
   5
   6 [ Upstream commit 5b5fd3c94eef69dcfaa8648198e54c92e5687d6d ]
   7
   8 Current code already uses d_strtoul_nonzero() to convert input string
   9 to an unsigned integer, to make sure writeback_rate_p_term_inverse
  10 won't be zero value. But overflow may happen when converting input
  11 string to an unsigned integer value by d_strtoul_nonzero(), then
  12 dc->writeback_rate_p_term_inverse can still be set to 0 even if the
  13 sysfs file input value is not zero, e.g. 4294967296 (a.k.a UINT_MAX+1).
  14
  15 If dc->writeback_rate_p_term_inverse is set to 0, it might cause a
  16 dev-zero error in following code from __update_writeback_rate(),
  17         int64_t proportional_scaled =
  18                 div_s64(error, dc->writeback_rate_p_term_inverse);
  19
  20 This patch replaces d_strtoul_nonzero() by sysfs_strtoul_clamp() and
  21 limit the value range in [1, UINT_MAX]. Then the unsigned integer
  22 overflow and dev-zero error can be avoided.
  23
  24 Signed-off-by: Coly Li <colyli@suse.de>
  25 Signed-off-by: Jens Axboe <axboe@kernel.dk>
  26 Signed-off-by: Sasha Levin <sashal@kernel.org>
  27 ---
  28  drivers/md/bcache/sysfs.c | 4 +++-
  29  1 file changed, 3 insertions(+), 1 deletion(-)
  30
  31 diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
  32 index 503ad954ccc0..d9481640b3e1 100644
  33 --- a/drivers/md/bcache/sysfs.c
  34 +++ b/drivers/md/bcache/sysfs.c
  35 @@ -286,7 +286,9 @@ STORE(__cached_dev)
  36         sysfs_strtoul_clamp(writeback_rate_i_term_inverse,
  37                             dc->writeback_rate_i_term_inverse,
  38                             1, UINT_MAX);
  39 -       d_strtoul_nonzero(writeback_rate_p_term_inverse);
  40 +       sysfs_strtoul_clamp(writeback_rate_p_term_inverse,
  41 +                           dc->writeback_rate_p_term_inverse,
  42 +                           1, UINT_MAX);
  43         d_strtoul_nonzero(writeback_rate_minimum);
  44
  45         sysfs_strtoul_clamp(io_error_limit, dc->error_limit, 0, INT_MAX);
  46 --
  47 2.19.1
  48