Messages in this thread | | | Date | Sun, 28 Apr 2019 06:47:22 -0700 | From | Jaegeuk Kim <> | Subject | Re: [PATCH 1/2] f2fs: fix to avoid potential negative .f_bfree |
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On 04/26, Chao Yu wrote: > When calculating .f_bfree value in f2fs_statfs(), sbi->unusable_block_count > can be increased after the judgment condition, result in overflow of > .f_bfree in later calculation. This patch fixes to use a temporary signed > variable to save the calculation result of .f_bfree. > > if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) > buf->f_bfree = 0; > else > buf->f_bfree -= sbi->unusable_block_count;
Do we just need stat_lock for this?
> > Signed-off-by: Chao Yu <yuchao0@huawei.com> > --- > fs/f2fs/super.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c > index 2376bb01b5c4..fcc9793dbc2c 100644 > --- a/fs/f2fs/super.c > +++ b/fs/f2fs/super.c > @@ -1216,6 +1216,7 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) > u64 id = huge_encode_dev(sb->s_bdev->bd_dev); > block_t total_count, user_block_count, start_count; > u64 avail_node_count; > + long long bfree; > > total_count = le64_to_cpu(sbi->raw_super->block_count); > user_block_count = sbi->user_block_count; > @@ -1226,10 +1227,12 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) > buf->f_blocks = total_count - start_count; > buf->f_bfree = user_block_count - valid_user_blocks(sbi) - > sbi->current_reserved_blocks; > - if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) > + > + bfree = buf->f_bfree - sbi->unusable_block_count; > + if (unlikely(bfree < 0)) > buf->f_bfree = 0; > else > - buf->f_bfree -= sbi->unusable_block_count; > + buf->f_bfree = bfree; > > if (buf->f_bfree > F2FS_OPTION(sbi).root_reserved_blocks) > buf->f_bavail = buf->f_bfree - > -- > 2.18.0.rc1
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