Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: add F2FS_IOC_TRIM_FILE ioctl | From | Chao Yu <> | Date | Tue, 9 Jun 2020 09:15:11 +0800 |
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On 2020/6/8 20:44, Daeho Jeong wrote: >>>> 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, > > Is it possible to access the old data of the block which has been > discarded already?
It's due to implementation of FTL, I guess it can in theoretically.
> Since FTL already sets the related bitmap to invalid even in the async > way, I thought > there is no way to access old data using the same logical address. > It's already invalidated.
In worse case, even it's invalid in bitmap, FTL can still load obsolete mapping entry, and access old page which contains key info.
> Have you seen any storage vendor allowing this? It's awful.
Not yet, since there is no restriction on any spec/doc, I prefer to choose to not trust vendors. :P
Thanks,
> > > 2020년 6월 8일 (월) 오후 4:43, Chao Yu <yuchao0@huawei.com>님이 작성: >> >> On 2020/6/8 15:19, Daeho Jeong wrote: >>> 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. :) >> >> IIRC, current solution is: >> >> - pin file >> - get all block addresses of file >> - write zero to block addresses >> - issue discard >> >> Is that correct? >> >> Could we handle those logic (zero out & discard) in new interface >> (may be named as {F2FS,EXT4}_IOC_SEC_TRIM_FILE)? then userspace logic >> could be quite simple later, and also memcpy could be avoid to make >> destruction process more efficient. >> >> Just raw proposal. :) >> >> Thanks, >> >>> 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@huawei.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@huawei.com>님이 작성: >>>>>> >>>>>> On 2020/6/5 12:27, Daeho Jeong wrote: >>>>>>> From: Daeho Jeong <daehojeong@google.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@google.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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