[PATCH 4.19 40/98] f2fs: fix to do sanity check in update_sit_entry

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zhiguo Niu <zhiguo.niu@unisoc.com>

[ Upstream commit 36959d18c3cf09b3c12157c6950e18652067de77 ]

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@unisoc.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 34090edc8ce25..6750cda692cc3 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2018,6 +2018,8 @@ 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;
@@ -2935,8 +2937,7 @@ void 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 (!__has_curseg_space(sbi, type))
 		sit_i->s_ops->allocate_segment(sbi, type, false);
-- 
2.43.0