From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chao Yu Subject: [PATCH] f2fs: fix potential overflow Date: Wed, 25 Apr 2018 19:38:17 +0800 Message-ID: <20180425113817.18189-1-chao@kernel.org> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu List-Id: linux-f2fs-devel.lists.sourceforge.net From: Chao Yu 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 --- 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