f2fs-tools: relocate chksum_offset for large_nat_bitmap feature

For large_nat_bitmap feature, there is a design flaw:

Previous:

struct f2fs_checkpoint layout:
+--------------------------+  0x0000
| checkpoint_ver           |
| ......                   |
| checksum_offset          |------+
| ......                   |      |
| sit_nat_version_bitmap[] |<-----|-------+
| ......                   |      |       |
| checksum_value           |<-----+       |
+--------------------------+  0x1000      |
|                          |      nat_bitmap + sit_bitmap
| payload blocks           |              |
|                          |              |
+--------------------------|<-------------+

Obviously, if nat_bitmap size + sit_bitmap size is larger than
MAX_BITMAP_SIZE_IN_CKPT, nat_bitmap or sit_bitmap may overlap
checkpoint checksum's position, once checkpoint() is triggered
from kernel, nat or sit bitmap will be damaged by checksum field.

In order to fix this, let's relocate checksum_value's position
to the head of sit_nat_version_bitmap as below, then nat/sit
bitmap and chksum value update will become safe.

After:

struct f2fs_checkpoint layout:
+--------------------------+  0x0000
| checkpoint_ver           |
| ......                   |
| checksum_offset          |------+
| ......                   |      |
| sit_nat_version_bitmap[] |<-----+
| ......                   |<-------------+
|                          |              |
+--------------------------+  0x1000      |
|                          |      nat_bitmap + sit_bitmap
| payload blocks           |              |
|                          |              |
+--------------------------|<-------------+

Related report and discussion:

https://sourceforge.net/p/linux-f2fs/mailman/message/36642346/

In addition, during writing checkpoint, if large_nat_bitmap feature is
enabled, we need to set CP_LARGE_NAT_BITMAP_FLAG flag in checkpoint.

Reported-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

8 files changed, 73 insertions, 5 deletions

diff --git a/fsck/f2fs.h b/fsck/f2fs.h
index 93f01e5..4dc6698 100644
--- a/fsck/f2fs.h
+++ b/fsck/f2fs.h
@@ -270,9 +270,16 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 	int offset;
 
 	if (is_set_ckpt_flags(ckpt, CP_LARGE_NAT_BITMAP_FLAG)) {
+		unsigned int chksum_size = 0;
+
 		offset = (flag == SIT_BITMAP) ?
 			le32_to_cpu(ckpt->nat_ver_bitmap_bytesize) : 0;
-		return &ckpt->sit_nat_version_bitmap + offset;
+
+		if (le32_to_cpu(ckpt->checksum_offset) ==
+					CP_MIN_CHKSUM_OFFSET)
+			chksum_size = sizeof(__le32);
+
+		return &ckpt->sit_nat_version_bitmap + offset + chksum_size;
 	}
 
 	if (le32_to_cpu(F2FS_RAW_SUPER(sbi)->cp_payload) > 0) {
diff --git a/fsck/fsck.c b/fsck/fsck.c
index a379a30..fe48071 100644
--- a/fsck/fsck.c
+++ b/fsck/fsck.c
@@ -1909,6 +1909,19 @@ int fsck_chk_meta(struct f2fs_sb_info *sbi)
 	return 0;
 }
 
+void fsck_chk_checkpoint(struct f2fs_sb_info *sbi)
+{
+	struct f2fs_checkpoint *cp = F2FS_CKPT(sbi);
+
+	if (get_cp(ckpt_flags) & CP_LARGE_NAT_BITMAP_FLAG) {
+		if (get_cp(checksum_offset) != CP_MIN_CHKSUM_OFFSET) {
+			ASSERT_MSG("Deprecated layout of large_nat_bitmap, "
+				"chksum_offset:%u", get_cp(checksum_offset));
+			c.fix_chksum = 1;
+		}
+	}
+}
+
 void fsck_init(struct f2fs_sb_info *sbi)
 {
 	struct f2fs_fsck *fsck = F2FS_FSCK(sbi);
@@ -2009,6 +2022,23 @@ static void flush_curseg_sit_entries(struct f2fs_sb_info *sbi)
 	free(sit_blk);
 }
 
+static void fix_checksum(struct f2fs_sb_info *sbi)
+{
+	struct f2fs_checkpoint *cp = F2FS_CKPT(sbi);
+	struct f2fs_nm_info *nm_i = NM_I(sbi);
+	struct sit_info *sit_i = SIT_I(sbi);
+	void *bitmap_offset;
+
+	if (!c.fix_chksum)
+		return;
+
+	bitmap_offset = cp->sit_nat_version_bitmap + sizeof(__le32);
+
+	memcpy(bitmap_offset, nm_i->nat_bitmap, nm_i->bitmap_size);
+	memcpy(bitmap_offset + nm_i->bitmap_size,
+			sit_i->sit_bitmap, sit_i->bitmap_size);
+}
+
 static void fix_checkpoint(struct f2fs_sb_info *sbi)
 {
 	struct f2fs_fsck *fsck = F2FS_FSCK(sbi);
@@ -2030,6 +2060,12 @@ static void fix_checkpoint(struct f2fs_sb_info *sbi)
 		flags |= CP_TRIMMED_FLAG;
 	if (is_set_ckpt_flags(cp, CP_DISABLED_FLAG))
 		flags |= CP_DISABLED_FLAG;
+	if (is_set_ckpt_flags(cp, CP_LARGE_NAT_BITMAP_FLAG)) {
+		flags |= CP_LARGE_NAT_BITMAP_FLAG;
+		set_cp(checksum_offset, CP_MIN_CHKSUM_OFFSET);
+	} else {
+		set_cp(checksum_offset, CP_CHKSUM_OFFSET);
+	}
 
 	if (flags & CP_UMOUNT_FLAG)
 		cp_blocks = 8;
@@ -2709,6 +2745,7 @@ int fsck_verify(struct f2fs_sb_info *sbi)
 				write_curseg_info(sbi);
 				flush_curseg_sit_entries(sbi);
 			}
+			fix_checksum(sbi);
 			fix_checkpoint(sbi);
 		} else if (is_set_ckpt_flags(cp, CP_FSCK_FLAG) ||
 			is_set_ckpt_flags(cp, CP_QUOTA_NEED_FSCK_FLAG)) {
diff --git a/fsck/fsck.h b/fsck/fsck.h
index 5895eec..c56e733 100644
--- a/fsck/fsck.h
+++ b/fsck/fsck.h
@@ -154,6 +154,7 @@ extern int fsck_chk_dentry_blk(struct f2fs_sb_info *, u32, struct child_info *,
 		int, int);
 int fsck_chk_inline_dentries(struct f2fs_sb_info *, struct f2fs_node *,
 		struct child_info *);
+void fsck_chk_checkpoint(struct f2fs_sb_info *sbi);
 int fsck_chk_meta(struct f2fs_sb_info *sbi);
 int fsck_chk_curseg_info(struct f2fs_sb_info *);
 void pretty_print_filename(const u8 *raw_name, u32 len,
diff --git a/fsck/main.c b/fsck/main.c
index 30fdbf2..d844820 100644
--- a/fsck/main.c
+++ b/fsck/main.c
@@ -616,6 +616,8 @@ static void do_fsck(struct f2fs_sb_info *sbi)
 		c.fix_on = 1;
 	}
 
+	fsck_chk_checkpoint(sbi);
+
 	fsck_chk_quota_node(sbi);
 
 	/* Traverse all block recursively from root inode */
diff --git a/fsck/mount.c b/fsck/mount.c
index 4eeeb6e..21d71d4 100644
--- a/fsck/mount.c
+++ b/fsck/mount.c
@@ -764,7 +764,8 @@ static int verify_checksum_chksum(struct f2fs_checkpoint *cp)
 	unsigned int chksum_offset = get_cp(checksum_offset);
 	unsigned int crc, cal_crc;
 
-	if (chksum_offset > CP_CHKSUM_OFFSET) {
+	if (chksum_offset < CP_MIN_CHKSUM_OFFSET ||
+			chksum_offset > CP_CHKSUM_OFFSET) {
 		MSG(0, "\tInvalid CP CRC offset: %u\n", chksum_offset);
 		return -1;
 	}
@@ -2362,6 +2363,12 @@ void write_checkpoint(struct f2fs_sb_info *sbi)
 		flags |= CP_TRIMMED_FLAG;
 	if (is_set_ckpt_flags(cp, CP_DISABLED_FLAG))
 		flags |= CP_DISABLED_FLAG;
+	if (is_set_ckpt_flags(cp, CP_LARGE_NAT_BITMAP_FLAG)) {
+		flags |= CP_LARGE_NAT_BITMAP_FLAG;
+		set_cp(checksum_offset, CP_MIN_CHKSUM_OFFSET);
+	} else {
+		set_cp(checksum_offset, CP_CHKSUM_OFFSET);
+	}
 
 	set_cp(free_segment_count, get_free_segments(sbi));
 	set_cp(valid_block_count, sbi->total_valid_block_count);
diff --git a/fsck/resize.c b/fsck/resize.c
index 5537a73..fc563f2 100644
--- a/fsck/resize.c
+++ b/fsck/resize.c
@@ -514,6 +514,11 @@ static void rebuild_checkpoint(struct f2fs_sb_info *sbi,
 	flags = update_nat_bits_flags(new_sb, cp, get_cp(ckpt_flags));
 	if (flags & CP_COMPACT_SUM_FLAG)
 		flags &= ~CP_COMPACT_SUM_FLAG;
+	if (flags & CP_LARGE_NAT_BITMAP_FLAG)
+		set_cp(checksum_offset, CP_MIN_CHKSUM_OFFSET);
+	else
+		set_cp(checksum_offset, CP_CHKSUM_OFFSET);
+
 	set_cp(ckpt_flags, flags);
 
 	memcpy(new_cp, cp, (unsigned char *)cp->sit_nat_version_bitmap -
diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
index 0e948fd..a347033 100644
--- a/include/f2fs_fs.h
+++ b/include/f2fs_fs.h
@@ -382,6 +382,7 @@ struct f2fs_configuration {
 	int ro;
 	int preserve_limits;		/* preserve quota limits */
 	int large_nat_bitmap;
+	int fix_chksum;			/* fix old cp.chksum position */
 	__le32 feature;			/* defined features */
 
 	/* mkfs parameters */
@@ -692,10 +693,15 @@ struct f2fs_checkpoint {
 	unsigned char sit_nat_version_bitmap[1];
 } __attribute__((packed));
 
+#define CP_BITMAP_OFFSET	\
+	(offsetof(struct f2fs_checkpoint, sit_nat_version_bitmap))
+#define CP_MIN_CHKSUM_OFFSET	CP_BITMAP_OFFSET
+
+#define MIN_NAT_BITMAP_SIZE	64
 #define MAX_SIT_BITMAP_SIZE_IN_CKPT    \
-	(CP_CHKSUM_OFFSET - sizeof(struct f2fs_checkpoint) + 1 - 64)
+	(CP_CHKSUM_OFFSET - CP_BITMAP_OFFSET - MIN_NAT_BITMAP_SIZE)
 #define MAX_BITMAP_SIZE_IN_CKPT	\
-	(CP_CHKSUM_OFFSET - sizeof(struct f2fs_checkpoint) + 1)
+	(CP_CHKSUM_OFFSET - CP_BITMAP_OFFSET)
 
 /*
  * For orphan inode management
diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
index e7ad072..bf4c6fe 100644
--- a/mkfs/f2fs_format.c
+++ b/mkfs/f2fs_format.c
@@ -690,7 +690,10 @@ static int f2fs_write_check_point_pack(void)
 	set_cp(nat_ver_bitmap_bytesize, ((get_sb(segment_count_nat) / 2) <<
 			 get_sb(log_blocks_per_seg)) / 8);
 
-	set_cp(checksum_offset, CP_CHKSUM_OFFSET);
+	if (c.large_nat_bitmap)
+		set_cp(checksum_offset, CP_MIN_CHKSUM_OFFSET);
+	else
+		set_cp(checksum_offset, CP_CHKSUM_OFFSET);
 
 	crc = f2fs_checkpoint_chksum(cp);
 	*((__le32 *)((unsigned char *)cp + get_cp(checksum_offset))) =