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Subject: Re: [PATCH v2 2/2] f2fs: introduce DATA_GENERIC_ENHANCE
To:     Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
References: <20190415072632.2158-1-yuchao0@huawei.com>
 <20190415072632.2158-2-yuchao0@huawei.com>
 <20190424093613.GA45953@jaegeuk-macbookpro.roam.corp.google.com>
From:   Chao Yu <chao@kernel.org>
Message-ID: <2a519411-b9bb-f153-c8b9-8eaca1f66837@kernel.org>
Date:   Wed, 24 Apr 2019 23:06:34 +0800
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On 2019-4-24 17:36, Jaegeuk Kim wrote:
> On 04/15, Chao Yu wrote:
>> Previously, f2fs_is_valid_blkaddr(, blkaddr, DATA_GENERIC) will check
>> whether @blkaddr locates in main area or not.
>>
>> That check is weak, since the block address in range of main area can
>> point to the address which is not valid in segment info table, and we
>> can not detect such condition, we may suffer worse corruption as system
>> continues running.
>>
>> So this patch introduce DATA_GENERIC_ENHANCE to enhance the sanity check
>> which trigger SIT bitmap check rather than only range check.
>>
>> This patch did below changes as wel:
>> - set SBI_NEED_FSCK in f2fs_is_valid_blkaddr().
>> - get rid of is_valid_data_blkaddr() to avoid panic if blkaddr is invalid.
>> - introduce verify_fio_blkaddr() to wrap fio {new,old}_blkaddr validation check.
>> - spread blkaddr check in:
>>  * f2fs_get_node_info()
>>  * __read_out_blkaddrs()
>>  * f2fs_submit_page_read()
>>  * ra_data_block()
>>  * do_recover_data()
>>
>> This patch can fix bug reported from bugzilla below:
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=203215
>> https://bugzilla.kernel.org/show_bug.cgi?id=203223
>> https://bugzilla.kernel.org/show_bug.cgi?id=203231
>> https://bugzilla.kernel.org/show_bug.cgi?id=203235
>> https://bugzilla.kernel.org/show_bug.cgi?id=203241
> 
> Hi Chao,
> 
> This introduces failures on xfstests/generic/446, and I'm testing the below
> patch on top of this. Could you check this patch, so that I could combine
> both of them?
> 
> From 8c1808c1743ad75d1ad8d1dc5a53910edaf7afd7 Mon Sep 17 00:00:00 2001
> From: Jaegeuk Kim <jaegeuk@kernel.org>
> Date: Wed, 24 Apr 2019 00:21:07 +0100
> Subject: [PATCH] f2fs: consider data race on read and truncation on
>  DATA_GENERIC_ENHANCE
> 
> DATA_GENERIC_ENHANCE enhanced to validate block addresses on read/write paths.
> But, xfstest/generic/446 compalins some generated kernel messages saying invalid
> bitmap was detected when reading a block. The reaons is, when we get the
> block addresses from extent_cache, there is no lock to synchronize it from
> truncating the blocks in parallel.
> 
> This patch tries to return EFAULT without warning and setting SBI_NEED_FSCK
> in this case.
> 
> Fixes: ("f2fs: introduce DATA_GENERIC_ENHANCE")
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/checkpoint.c | 35 ++++++++++++++++++-----------------
>  fs/f2fs/data.c       | 25 ++++++++++++++++++-------
>  fs/f2fs/f2fs.h       |  6 ++++++
>  fs/f2fs/gc.c         |  9 ++++++---
>  4 files changed, 48 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index e37fbbf843a5..805a33088e82 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -130,26 +130,28 @@ struct page *f2fs_get_tmp_page(struct f2fs_sb_info *sbi, pgoff_t index)
>  	return __get_meta_page(sbi, index, false);
>  }
>  
> -static bool __is_bitmap_valid(struct f2fs_sb_info *sbi, block_t blkaddr)
> +static bool __is_bitmap_valid(struct f2fs_sb_info *sbi, block_t blkaddr,
> +							int type)
>  {
>  	struct seg_entry *se;
>  	unsigned int segno, offset;
>  	bool exist;
>  
> +	if (type != DATA_GENERIC_ENHANCE && type != DATA_GENERIC_ENHANCE_READ)
> +		return true;
> +
>  	segno = GET_SEGNO(sbi, blkaddr);
>  	offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);
>  	se = get_seg_entry(sbi, segno);
>  
>  	exist = f2fs_test_bit(offset, se->cur_valid_map);
> -
> -	if (!exist) {
> +	if (!exist && type == DATA_GENERIC_ENHANCE) {
>  		f2fs_msg(sbi->sb, KERN_ERR, "Inconsistent error "
>  			"blkaddr:%u, sit bitmap:%d", blkaddr, exist);
>  		set_sbi_flag(sbi, SBI_NEED_FSCK);
>  		WARN_ON(1);
> -		return false;
>  	}
> -	return true;
> +	return exist;
>  }
>  
>  bool f2fs_is_valid_blkaddr(struct f2fs_sb_info *sbi,
> @@ -173,23 +175,22 @@ bool f2fs_is_valid_blkaddr(struct f2fs_sb_info *sbi,
>  			return false;
>  		break;
>  	case META_POR:
> +		if (unlikely(blkaddr >= MAX_BLKADDR(sbi) ||
> +			blkaddr < MAIN_BLKADDR(sbi)))
> +			return false;
> +		break;
>  	case DATA_GENERIC:
>  	case DATA_GENERIC_ENHANCE:
> +	case DATA_GENERIC_ENHANCE_READ:
>  		if (unlikely(blkaddr >= MAX_BLKADDR(sbi) ||
> -			blkaddr < MAIN_BLKADDR(sbi))) {
> -			if (type == DATA_GENERIC ||
> -				type == DATA_GENERIC_ENHANCE) {
> -				f2fs_msg(sbi->sb, KERN_WARNING,
> -					"access invalid blkaddr:%u", blkaddr);
> -				set_sbi_flag(sbi, SBI_NEED_FSCK);
> -				WARN_ON(1);
> -			}
> +				blkaddr < MAIN_BLKADDR(sbi))) {
> +			f2fs_msg(sbi->sb, KERN_WARNING,
> +				"access invalid blkaddr:%u", blkaddr);
> +			set_sbi_flag(sbi, SBI_NEED_FSCK);
> +			WARN_ON(1);
>  			return false;
>  		} else {
> -			if (type == DATA_GENERIC_ENHANCE) {
> -				if (!__is_bitmap_valid(sbi, blkaddr))
> -					return false;
> -			}
> +			return __is_bitmap_valid(sbi, blkaddr, type);
>  		}
>  		break;
>  	case META_GENERIC:
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 34d248ac9e0f..d32a82f25f5a 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -564,9 +564,6 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>  	struct bio_post_read_ctx *ctx;
>  	unsigned int post_read_steps = 0;
>  
> -	if (!f2fs_is_valid_blkaddr(sbi, blkaddr, DATA_GENERIC_ENHANCE))
> -		return ERR_PTR(-EFAULT);
> -
>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
>  	if (!bio)
>  		return ERR_PTR(-ENOMEM);
> @@ -597,9 +594,6 @@ static int f2fs_submit_page_read(struct inode *inode, struct page *page,
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>  	struct bio *bio;
>  
> -	if (!f2fs_is_valid_blkaddr(sbi, blkaddr, DATA_GENERIC_ENHANCE))
> -		return -EFAULT;
> -
>  	bio = f2fs_grab_read_bio(inode, blkaddr, 1, 0);
>  	if (IS_ERR(bio))
>  		return PTR_ERR(bio);
> @@ -741,6 +735,11 @@ struct page *f2fs_get_read_data_page(struct inode *inode, pgoff_t index,
>  
>  	if (f2fs_lookup_extent_cache(inode, index, &ei)) {
>  		dn.data_blkaddr = ei.blk + index - ei.fofs;
> +		if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), dn.data_blkaddr,
> +						DATA_GENERIC_ENHANCE_READ)) {

If I'm not missing anything, we just need use DATA_GENERIC_ENHANCE_READ to cover
below two paths:
- gc_data_segment -> f2fs_get_read_data_page
- move_data_page -> f2fs_get_lock_data_page -> f2fs_get_read_data_page

Other paths which calls f2fs_get_read_data_page is safe to verify blkaddr with
DATA_GENERIC_ENHANCE?

> +			err = -EFAULT;
> +			goto put_err;
> +		}
>  		goto got_it;
>  	}
>  
> @@ -754,6 +753,13 @@ struct page *f2fs_get_read_data_page(struct inode *inode, pgoff_t index,
>  		err = -ENOENT;
>  		goto put_err;
>  	}
> +	if (dn.data_blkaddr != NEW_ADDR &&
> +			!f2fs_is_valid_blkaddr(F2FS_I_SB(inode),
> +						dn.data_blkaddr,
> +						DATA_GENERIC_ENHANCE)) {
> +		err = -EFAULT;
> +		goto put_err;
> +	}
>  got_it:
>  	if (PageUptodate(page)) {
>  		unlock_page(page);
> @@ -1566,7 +1572,7 @@ static int f2fs_read_single_page(struct inode *inode, struct page *page,
>  		}
>  
>  		if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), block_nr,
> -							DATA_GENERIC_ENHANCE)) {
> +						DATA_GENERIC_ENHANCE_READ)) {
>  			ret = -EFAULT;
>  			goto out;
>  		}
> @@ -2528,6 +2534,11 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
>  		zero_user_segment(page, 0, PAGE_SIZE);
>  		SetPageUptodate(page);
>  	} else {
> +		if (!f2fs_is_valid_blkaddr(sbi, blkaddr,
> +				DATA_GENERIC_ENHANCE_READ)) {

Need DATA_GENERIC_ENHANCE because write() is exclusive with truncate() due to
inode_lock()?

Thanks,

> +			err = -EFAULT;
> +			goto fail;
> +		}
>  		err = f2fs_submit_page_read(inode, page, blkaddr);
>  		if (err)
>  			goto fail;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index f5ffc09705eb..533fafca68f4 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -212,6 +212,12 @@ enum {
>  	META_POR,
>  	DATA_GENERIC,		/* check range only */
>  	DATA_GENERIC_ENHANCE,	/* strong check on range and segment bitmap */
> +	DATA_GENERIC_ENHANCE_READ,	/*
> +					 * strong check on range and segment
> +					 * bitmap but no warning due to race
> +					 * condition of read on truncated area
> +					 * by extent_cache
> +					 */
>  	META_GENERIC,
>  };
>  
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 3a097949b5d4..963fb4571fd9 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -656,6 +656,11 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>  
>  	if (f2fs_lookup_extent_cache(inode, index, &ei)) {
>  		dn.data_blkaddr = ei.blk + index - ei.fofs;
> +		if (unlikely(!f2fs_is_valid_blkaddr(sbi, dn.data_blkaddr,
> +						DATA_GENERIC_ENHANCE_READ))) {
> +			err = -EFAULT;
> +			goto put_page;
> +		}
>  		goto got_it;
>  	}
>  
> @@ -669,14 +674,12 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>  		err = -ENOENT;
>  		goto put_page;
>  	}
> -
> -got_it:
>  	if (unlikely(!f2fs_is_valid_blkaddr(sbi, dn.data_blkaddr,
>  						DATA_GENERIC_ENHANCE))) {
>  		err = -EFAULT;
>  		goto put_page;
>  	}
> -
> +got_it:
>  	/* read page */
>  	fio.page = page;
>  	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>