[PATCH] f2fs: fix to do sanity check in update_sit_entry

[Zhiguo Niu]

If GET_SEGNO return NULL_SEGNO for some unecpected case,
update_sit_entry will access invalid memory address,
cause system crash. It is better to do sanity check about
GET_SEGNO just like update_segment_mtime & locate_dirty_segment.

Also remove some redundant judgment code.

Signed-off-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
---
 fs/f2fs/segment.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index c616e7a..f8a823f 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2407,6 +2407,8 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
 #endif
 
 	segno = GET_SEGNO(sbi, blkaddr);
+	if (segno == NULL_SEGNO)
+		return;
 
 	se = get_seg_entry(sbi, segno);
 	new_vblocks = se->valid_blocks + del;
@@ -3504,8 +3506,7 @@ int f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
 	 * since SSR needs latest valid block information.
 	 */
 	update_sit_entry(sbi, *new_blkaddr, 1);
-	if (GET_SEGNO(sbi, old_blkaddr) != NULL_SEGNO)
-		update_sit_entry(sbi, old_blkaddr, -1);
+	update_sit_entry(sbi, old_blkaddr, -1);
 
 	/*
 	 * If the current segment is full, flush it out and replace it with a
-- 
1.9.1