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Message-ID: <CACOAw_wVEw3+Kyz2HvvanhhP2_-xQy9wjfpDt5G0ahXM8o-V-Q@mail.gmail.com>
Date: Mon, 8 Jun 2020 16:19:43 +0900
From: Daeho Jeong <daeho43@...il.com>
To: Chao Yu <yuchao0@...wei.com>
Cc: linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: add F2FS_IOC_TRIM_FILE ioctl
Yes, I agree with you about each vendor has different implementation on discard.
So, we might be gonna use the combination of zeroing and send discards
for a more
secure solution. :)
I think we still need a discard interface to unmap from the mapping
table of the storage device side.
Thanks,
2020년 6월 8일 (월) 오후 3:57, Chao Yu <yuchao0@...wei.com>님이 작성:
>
> On 2020/6/8 11:36, Daeho Jeong wrote:
> > Yes, this is for security key destruction.
> >
> > AFAIK, discard will unmap the data block and, after done it,
> > we can read either zero data or garbage data from that block depending
> > on eMMC/UFS.
>
> Since spec didn't restrict how vendor implement the erase interface, so
> in order to enhance performance of discard interface, vendor could implement
> it as an async one, which may not zero mapping entry(L1 table), instead, it
> could set related bitmap to invalid that mapping entry, than later if device
> allow user to access that invalid mapping entry, key info may be explosed,
>
> It's completely up to how vendor implement the interface, so I think there is
> still risk to use discard.
>
> Thanks,
>
> > In a view point of read data, it might be the same with zeroing the data block.
> > However, since we can even unmap that block, I believe discard is
> > safer than zeroing out.
> >
> > 2020년 6월 8일 (월) 오전 11:46, Chao Yu <yuchao0@...wei.com>님이 작성:
> >>
> >> On 2020/6/5 12:27, Daeho Jeong wrote:
> >>> From: Daeho Jeong <daehojeong@...gle.com>
> >>>
> >>> Added a new ioctl to send discard commands to whole data area of
> >>> a regular file for security reason.
> >>
> >> I guess this interface is introduced for security key destruction, if I'm
> >> right, however, IIRC, discard(erase) semantics in eMMC/UFS spec won't
> >> guarantee that data which was discard could be zeroed out, so after discard,
> >> the key still have risk of exposure. So instead, should we use sb_issue_zeroout()?
> >>
> >> Thanks,
> >>
> >>>
> >>> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> >>> ---
> >>> fs/f2fs/f2fs.h | 1 +
> >>> fs/f2fs/file.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++
> >>> 2 files changed, 130 insertions(+)
> >>>
> >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >>> index c812fb8e2d9c..9ae81d0fefa0 100644
> >>> --- a/fs/f2fs/f2fs.h
> >>> +++ b/fs/f2fs/f2fs.h
> >>> @@ -434,6 +434,7 @@ static inline bool __has_cursum_space(struct f2fs_journal *journal,
> >>> _IOR(F2FS_IOCTL_MAGIC, 18, __u64)
> >>> #define F2FS_IOC_RESERVE_COMPRESS_BLOCKS \
> >>> _IOR(F2FS_IOCTL_MAGIC, 19, __u64)
> >>> +#define F2FS_IOC_TRIM_FILE _IO(F2FS_IOCTL_MAGIC, 20)
> >>>
> >>> #define F2FS_IOC_GET_VOLUME_NAME FS_IOC_GETFSLABEL
> >>> #define F2FS_IOC_SET_VOLUME_NAME FS_IOC_SETFSLABEL
> >>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >>> index dfa1ac2d751a..58507bb5649c 100644
> >>> --- a/fs/f2fs/file.c
> >>> +++ b/fs/f2fs/file.c
> >>> @@ -3749,6 +3749,132 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg)
> >>> return ret;
> >>> }
> >>>
> >>> +static int f2fs_trim_file(struct file *filp)
> >>> +{
> >>> + struct inode *inode = file_inode(filp);
> >>> + struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>> + struct address_space *mapping = inode->i_mapping;
> >>> + struct bio *bio = NULL;
> >>> + struct block_device *prev_bdev = NULL;
> >>> + loff_t file_size;
> >>> + pgoff_t index, pg_start = 0, pg_end;
> >>> + block_t prev_block = 0, len = 0;
> >>> + int ret = 0;
> >>> +
> >>> + if (!f2fs_hw_support_discard(sbi))
> >>> + return -EOPNOTSUPP;
> >>> +
> >>> + if (!S_ISREG(inode->i_mode) || f2fs_is_atomic_file(inode) ||
> >>> + f2fs_compressed_file(inode))
> >>> + return -EINVAL;
> >>> +
> >>> + if (f2fs_readonly(sbi->sb))
> >>> + return -EROFS;
> >>> +
> >>> + ret = mnt_want_write_file(filp);
> >>> + if (ret)
> >>> + return ret;
> >>> +
> >>> + inode_lock(inode);
> >>> +
> >>> + file_size = i_size_read(inode);
> >>> + if (!file_size)
> >>> + goto err;
> >>> + pg_end = (pgoff_t)round_up(file_size, PAGE_SIZE) >> PAGE_SHIFT;
> >>> +
> >>> + ret = f2fs_convert_inline_inode(inode);
> >>> + if (ret)
> >>> + goto err;
> >>> +
> >>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >>> + down_write(&F2FS_I(inode)->i_mmap_sem);
> >>> +
> >>> + ret = filemap_write_and_wait(mapping);
> >>> + if (ret)
> >>> + goto out;
> >>> +
> >>> + truncate_inode_pages(mapping, 0);
> >>> +
> >>> + for (index = pg_start; index < pg_end;) {
> >>> + struct dnode_of_data dn;
> >>> + unsigned int end_offset;
> >>> +
> >>> + set_new_dnode(&dn, inode, NULL, NULL, 0);
> >>> + ret = f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE);
> >>> + if (ret)
> >>> + goto out;
> >>> +
> >>> + end_offset = ADDRS_PER_PAGE(dn.node_page, inode);
> >>> + if (pg_end < end_offset + index)
> >>> + end_offset = pg_end - index;
> >>> +
> >>> + for (; dn.ofs_in_node < end_offset;
> >>> + dn.ofs_in_node++, index++) {
> >>> + struct block_device *cur_bdev;
> >>> + block_t blkaddr = f2fs_data_blkaddr(&dn);
> >>> +
> >>> + if (__is_valid_data_blkaddr(blkaddr)) {
> >>> + if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode),
> >>> + blkaddr, DATA_GENERIC_ENHANCE)) {
> >>> + ret = -EFSCORRUPTED;
> >>> + goto out;
> >>> + }
> >>> + } else
> >>> + continue;
> >>> +
> >>> + cur_bdev = f2fs_target_device(sbi, blkaddr, NULL);
> >>> + if (f2fs_is_multi_device(sbi)) {
> >>> + int i = f2fs_target_device_index(sbi, blkaddr);
> >>> +
> >>> + blkaddr -= FDEV(i).start_blk;
> >>> + }
> >>> +
> >>> + if (len) {
> >>> + if (prev_bdev == cur_bdev &&
> >>> + blkaddr == prev_block + len) {
> >>> + len++;
> >>> + } else {
> >>> + ret = __blkdev_issue_discard(prev_bdev,
> >>> + SECTOR_FROM_BLOCK(prev_block),
> >>> + SECTOR_FROM_BLOCK(len),
> >>> + GFP_NOFS, 0, &bio);
> >>> + if (ret)
> >>> + goto out;
> >>> +> + len = 0;
> >>> + }
> >>> + }
> >>> +
> >>> + if (!len) {
> >>> + prev_bdev = cur_bdev;
> >>> + prev_block = blkaddr;
> >>> + len = 1;
> >>> + }
> >>> + }
> >>> +
> >>> + f2fs_put_dnode(&dn);
> >>> + }
> >>> +
> >>> + if (len)
> >>> + ret = __blkdev_issue_discard(prev_bdev,
> >>> + SECTOR_FROM_BLOCK(prev_block),
> >>> + SECTOR_FROM_BLOCK(len),
> >>> + GFP_NOFS, 0, &bio);
> >>> +out:
> >>> + if (bio) {
> >>> + ret = submit_bio_wait(bio);
> >>> + bio_put(bio);
> >>> + }
> >>> +
> >>> + up_write(&F2FS_I(inode)->i_mmap_sem);
> >>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >>> +err:
> >>> + inode_unlock(inode);
> >>> + mnt_drop_write_file(filp);
> >>> +
> >>> + return ret;
> >>> +}
> >>> +
> >>> long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> >>> {
> >>> if (unlikely(f2fs_cp_error(F2FS_I_SB(file_inode(filp)))))
> >>> @@ -3835,6 +3961,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> >>> return f2fs_release_compress_blocks(filp, arg);
> >>> case F2FS_IOC_RESERVE_COMPRESS_BLOCKS:
> >>> return f2fs_reserve_compress_blocks(filp, arg);
> >>> + case F2FS_IOC_TRIM_FILE:
> >>> + return f2fs_trim_file(filp);
> >>> default:
> >>> return -ENOTTY;
> >>> }
> >>> @@ -4004,6 +4132,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> >>> case F2FS_IOC_GET_COMPRESS_BLOCKS:
> >>> case F2FS_IOC_RELEASE_COMPRESS_BLOCKS:
> >>> case F2FS_IOC_RESERVE_COMPRESS_BLOCKS:
> >>> + case F2FS_IOC_TRIM_FILE:
> >>> break;
> >>> default:
> >>> return -ENOIOCTLCMD;
> >>>
> > .
> >
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