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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: d600af236d ("f2fs: avoid unneeded loop in build_sit_entries")
Fixes: 1f43e2ad7b ("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>
This commit is contained in:
Chao Yu 2018-04-25 19:38:17 +08:00 committed by Jaegeuk Kim
parent b2532c6940
commit a9af3fdcc4
1 changed files with 7 additions and 4 deletions
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11
fs/f2fs/segment.c
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@ -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);