lkml.org 
[lkml]   [2018]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] f2fs: fix potential overflow
Date
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
\
 
 \ /
  Last update: 2018-04-25 13:39    [W:0.032 / U:5.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site