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
6 [ Upstream commit 5b5fd3c94eef69dcfaa8648198e54c92e5687d6d ]
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).
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);
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.
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>
28 drivers/md/bcache/sysfs.c | 4 +++-
29 1 file changed, 3 insertions(+), 1 deletion(-)
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,
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,
43 d_strtoul_nonzero(writeback_rate_minimum);
45 sysfs_strtoul_clamp(io_error_limit, dc->error_limit, 0, INT_MAX);