[PATCH v3] f2fs: avoid out-of-range memory access

[Ocean Chen]

blk_off might over 512 due to fs corrupt and should
be checked before being used.
Use ENTRIES_IN_SUM to protect invalid memory access.

--
v2:
- fix typo
v3:
- check blk_off before being used
--
Signed-off-by: Ocean Chen <oceanchen@xxxxxxxxxx>
---
 fs/f2fs/segment.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 8dee063c833f..c3eae3239345 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -3401,6 +3401,9 @@ static int read_compacted_summaries(struct f2fs_sb_info *sbi)
 		if (seg_i->alloc_type == SSR)
 			blk_off = sbi->blocks_per_seg;
 
+                if (blk_off >= ENTRIES_IN_SUM)
+                  return -EFAULT;
+
 		for (j = 0; j < blk_off; j++) {
 			struct f2fs_summary *s;
 			s = (struct f2fs_summary *)(kaddr + offset);
-- 
2.22.0.410.gd8fdbe21b5-goog