Messages in this thread Patch in this message | | | From | Chao Yu <> | Subject | [PATCH] f2fs: fix potential overflow | Date | Wed, 25 Apr 2018 19:38:17 +0800 |
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From: Chao Yu <yuchao0@huawei.com>
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> --- 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 a55647f61232..49fce2b56017 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -3692,14 +3692,17 @@ 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); -- 2.16.2.17.g38e79b1fd
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