f2fs: fix potential overflow

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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>

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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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fs/f2fs/segment.c

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