[PATCH 4.9 193/223] f2fs: avoid out-of-range memory access

[Greg Kroah-Hartman]

[ Upstream commit 56f3ce675103e3fb9e631cfb4131fc768bc23e9a ]

blkoff_off might over 512 due to fs corrupt or security
vulnerability. That should be checked before being using.

Use ENTRIES_IN_SUM to protect invalid value in cur_data_blkoff.

Signed-off-by: Ocean Chen <oceanchen@xxxxxxxxxx>
Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/f2fs/segment.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 2fb99a081de8..c983f7d28f03 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1709,6 +1709,11 @@ static int read_compacted_summaries(struct f2fs_sb_info *sbi)
 		seg_i = CURSEG_I(sbi, i);
 		segno = le32_to_cpu(ckpt->cur_data_segno[i]);
 		blk_off = le16_to_cpu(ckpt->cur_data_blkoff[i]);
+		if (blk_off > ENTRIES_IN_SUM) {
+			f2fs_bug_on(sbi, 1);
+			f2fs_put_page(page, 1);
+			return -EFAULT;
+		}
 		seg_i->next_segno = segno;
 		reset_curseg(sbi, i, 0);
 		seg_i->alloc_type = ckpt->alloc_type[i];
-- 
2.20.1