f2fs: fix to avoid potential memory corruption in __update_iostat_latency()

f2fs: fix to avoid potential memory corruption in __update_iostat_latency()

Add iotype sanity check to avoid potential memory corruption.
This is to fix the compile error below:

fs/f2fs/iostat.c:231 __update_iostat_latency() error: buffer overflow
'io_lat->peak_lat[type]' 3 <= 3

vim +228 fs/f2fs/iostat.c

  211  static inline void __update_iostat_latency(struct bio_iostat_ctx
	*iostat_ctx,
  212					enum iostat_lat_type type)
  213  {
  214		unsigned long ts_diff;
  215		unsigned int page_type = iostat_ctx->type;
  216		struct f2fs_sb_info *sbi = iostat_ctx->sbi;
  217		struct iostat_lat_info *io_lat = sbi->iostat_io_lat;
  218		unsigned long flags;
  219
  220		if (!sbi->iostat_enable)
  221			return;
  222
  223		ts_diff = jiffies - iostat_ctx->submit_ts;
  224		if (page_type >= META_FLUSH)
                                 ^^^^^^^^^^

  225			page_type = META;
  226
  227		spin_lock_irqsave(&sbi->iostat_lat_lock, flags);
 @228		io_lat->sum_lat[type][page_type] += ts_diff;
                                      ^^^^^^^^^
Mixup between META_FLUSH and NR_PAGE_TYPE leads to memory corruption.

Fixes: a4b6817625e7 ("f2fs: introduce periodic iostat io latency traces")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Suggested-by: Chao Yu <chao@kernel.org>
Suggested-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Yangtao Li <frank.li@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>