[PATCH v3 1/2] f2fs: fix to avoid potential memory corruption in __update_iostat_latency()

[Yangtao Li <frank.li@vivo.com>]

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>
---
v3:
-convert to warn
 fs/f2fs/iostat.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/iostat.c b/fs/f2fs/iostat.c
index ed8176939aa5..96637756eae8 100644
--- a/fs/f2fs/iostat.c
+++ b/fs/f2fs/iostat.c
@@ -223,8 +223,12 @@ static inline void __update_iostat_latency(struct bio_iostat_ctx *iostat_ctx,
 		return;
 
 	ts_diff = jiffies - iostat_ctx->submit_ts;
-	if (iotype >= META_FLUSH)
+	if (iotype == META_FLUSH) {
 		iotype = META;
+	} else if (iotype >= NR_PAGE_TYPE) {
+		f2fs_warn(sbi, "%s: %d over NR_PAGE_TYPE", __func__, iotype);
+		return;
+	}
 
 	if (rw == 0) {
 		idx = READ_IO;
-- 
2.25.1