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Date:   Wed, 24 Apr 2019 10:36:13 +0100
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH v2 2/2] f2fs: introduce DATA_GENERIC_ENHANCE
Message-ID: <20190424093613.GA45953@jaegeuk-macbookpro.roam.corp.google.com>
References: <20190415072632.2158-1-yuchao0@huawei.com>
 <20190415072632.2158-2-yuchao0@huawei.com>
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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)) {
+			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)) {
+			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;
-- 
2.19.0.605.g01d371f741-goog