Messages in this thread | | | From | OGAWA Hirofumi <> | Subject | Re: [PATCH] fat: Support fallocate on fat. | Date | Sun, 08 Jul 2012 22:06:56 +0900 |
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Namjae Jeon <linkinjeon@gmail.com> writes:
> +/* > + * preallocate space for a file. This implements fat's fallocate file > + * operation, which gets called from sys_fallocate system call. User > + * space requests len bytes at offset.If FALLOC_FL_KEEP_SIZE is set > + * we just allocate clusters without zeroing them out.Otherwise we > + * allocate and zero out clusters via an expanding truncate. > + */ > +static long fat_fallocate(struct file *file, int mode, > + loff_t offset, loff_t len) > +{ > + int err = 0; > + struct inode *inode = file->f_mapping->host; > + int cluster, nr_cluster, fclus, dclus, free_bytes, nr_bytes; > + struct super_block *sb = inode->i_sb; > + struct msdos_sb_info *sbi = MSDOS_SB(sb);
What happens if called for directory? And does this guarantee it never expose the uninitialized data userland?
> + /* No support for hole punch or other fallocate flags. */ > + if (mode & ~FALLOC_FL_KEEP_SIZE) > + return -EOPNOTSUPP; > > + if ((offset + len) <= MSDOS_I(inode)->mmu_private) { > + fat_msg(sb, KERN_ERR, > + "fat_fallocate():Blocks already allocated"); > + return -EINVAL; > + }
Please don't output any message by user error. And EINVAL is right behavior if (offset + len) < allocated size? Sounds like strange design.
> + if ((mode & FALLOC_FL_KEEP_SIZE)) { > + /* First compute the number of clusters to be allocated */ > + if (inode->i_size > 0) { > + err = fat_get_cluster(inode, FAT_ENT_EOF, > + &fclus, &dclus); > + if (err < 0) { > + fat_msg(sb, KERN_ERR, > + "fat_fallocate():fat_get_cluster() error");
Use "%s" and __func__. And looks like the error is normal (e.g. ENOSPC), so I don't see why it needs to report.
[...]
> + /* > + * calculate i_blocks and mmu_private from the actual number of > + * allocated clusters instead of doing it from file size.This ensures > + * that the preallocated disk space using FALLOC_FL_KEEP_SIZE is > + * persistent across remounts and writes go into the allocated clusters. > + */ > + fat_calc_dir_size(inode);
Looks like the wrong. If you didn't initialize preallocated space, the data never be exposed to userland. It is security bug.
> inode->i_blocks = ((inode->i_size + (sbi->cluster_size - 1)) > & ~((loff_t)sbi->cluster_size - 1)) >> 9; > + MSDOS_I(inode)->mmu_private = inode->i_size; > + /* restore i_size */ > + inode->i_size = le32_to_cpu(de->size); > > fat_time_fat2unix(sbi, &inode->i_mtime, de->time, de->date, 0); > if (sbi->options.isvfat) {
-- OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
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