Messages in this thread Patch in this message | | | From | Chao Yu <> | Subject | [PATCH 1/2] f2fs: fix to avoid potential negative .f_bfree | Date | Fri, 26 Apr 2019 17:57:53 +0800 |
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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;
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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