From a9af3fdcc4258af406879eca63d82e9d6baa892e Mon Sep 17 00:00:00 2001 From: Chao Yu Date: Wed, 25 Apr 2018 19:38:17 +0800 Subject: [PATCH] f2fs: fix potential overflow In build_sit_entries(), if valid_blocks in SIT block is smaller than valid_blocks in journal, for below calculation: sbi->discard_blks += old_valid_blocks - se->valid_blocks; There will be two times potential overflow: - old_valid_blocks - se->valid_blocks will overflow, and be a very large number. - sbi->discard_blks += result will overflow again, comes out a correct result accidently. Anyway, it should be fixed. Fixes: d600af236da5 ("f2fs: avoid unneeded loop in build_sit_entries") Fixes: 1f43e2ad7bff ("f2fs: introduce CP_TRIMMED_FLAG to avoid unneeded discard") Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim --- fs/f2fs/segment.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 1576b9d9a172..fec698d17d6a 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -3714,14 +3714,17 @@ static int build_sit_entries(struct f2fs_sb_info *sbi) } else { memcpy(se->discard_map, se->cur_valid_map, SIT_VBLOCK_MAP_SIZE); - sbi->discard_blks += old_valid_blocks - - se->valid_blocks; + sbi->discard_blks += old_valid_blocks; + sbi->discard_blks -= se->valid_blocks; } } - if (sbi->segs_per_sec > 1) + if (sbi->segs_per_sec > 1) { get_sec_entry(sbi, start)->valid_blocks += - se->valid_blocks - old_valid_blocks; + se->valid_blocks; + get_sec_entry(sbi, start)->valid_blocks -= + old_valid_blocks; + } } up_read(&curseg->journal_rwsem);