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 <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9723ad6..15fa9bd 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -3715,14 +3715,17 @@
} 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);