From c3b75a2199cdbfc1c335155fe143d842604b1baa Mon Sep 17 00:00:00 2001 From: Coly Li Date: Sat, 9 Feb 2019 12:53:05 +0800 Subject: bcache: fix potential div-zero error of writeback_rate_i_term_inverse dc->writeback_rate_i_term_inverse can be set via sysfs interface. It is in type unsigned int, and convert from input string by d_strtoul(). The problem is d_strtoul() does not check valid range of the input, if 4294967296 is written into sysfs file writeback_rate_i_term_inverse, an overflow of unsigned integer will happen and value 0 is set to dc->writeback_rate_i_term_inverse. In writeback.c:__update_writeback_rate(), there are following lines of code, integral_scaled = div_s64(dc->writeback_rate_integral, dc->writeback_rate_i_term_inverse); If dc->writeback_rate_i_term_inverse is set to 0 via sysfs interface, a div-zero error might be triggered in the above code. Therefore we need to add a range limitation in the sysfs interface, this is what this patch does, use sysfs_stroul_clamp() to replace d_strtoul() and restrict the input range in [1, UINT_MAX]. Signed-off-by: Coly Li Signed-off-by: Jens Axboe --- drivers/md/bcache/sysfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/md') diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c index e4519326594f..0fad46d3a8bd 100644 --- a/drivers/md/bcache/sysfs.c +++ b/drivers/md/bcache/sysfs.c @@ -302,7 +302,9 @@ STORE(__cached_dev) sysfs_strtoul_clamp(writeback_rate_update_seconds, dc->writeback_rate_update_seconds, 1, WRITEBACK_RATE_UPDATE_SECS_MAX); - d_strtoul(writeback_rate_i_term_inverse); + sysfs_strtoul_clamp(writeback_rate_i_term_inverse, + dc->writeback_rate_i_term_inverse, + 1, UINT_MAX); d_strtoul_nonzero(writeback_rate_p_term_inverse); d_strtoul_nonzero(writeback_rate_minimum); -- cgit