[PATCH v3] fsck.f2fs: sanitize invalid segment type during block update

[PATCH v3] fsck.f2fs: sanitize invalid segment type during block update

[Daeho Jeong]

From: Daeho Jeong <daehojeong@google.com>

If an invalid segment type (type < 0 || type >= NO_CHECK_TYPE) is read
from SIT during block update, update_block() now validates the type,
reports corruption via ASSERT_MSG(), fixes se->type directly, and falls
back to a valid active curseg type based on its SSA summary block type
when fix_on is enabled. find_next_free_block() also validates want_type to
prevent out-of-bounds accesses.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
---
v3: do not update se->orig_type.
v2: used ASSERT_MSG() instead of ERR_MSG().
    used the correct type info for fixed_type.
    fixed se->type on top of fixing the local type only.
---
 fsck/mount.c   |  5 +++++
 fsck/segment.c | 20 ++++++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/fsck/mount.c b/fsck/mount.c
index 6f640a0..1804403 100644
--- a/fsck/mount.c
+++ b/fsck/mount.c
@@ -3059,6 +3059,11 @@ int find_next_free_block(struct f2fs_sb_info *sbi, u64 *to, int left,
 	u64 end_blkaddr = (get_sb(segment_count_main) <<
 			get_sb(log_blocks_per_seg)) + get_sb(main_blkaddr);
 
+	if (want_type < 0 || want_type >= NO_CHECK_TYPE) {
+		ASSERT_MSG("Invalid segment type %d for block allocation", want_type);
+		return -EINVAL;
+	}
+
 	if (c.zoned_model == F2FS_ZONED_HM && !new_sec) {
 		struct curseg_info *curseg = CURSEG_I(sbi, want_type);
 		unsigned int segs_per_zone = sbi->segs_per_sec * sbi->secs_per_zone;
diff --git a/fsck/segment.c b/fsck/segment.c
index 96de22a..9f3fa0c 100644
--- a/fsck/segment.c
+++ b/fsck/segment.c
@@ -770,15 +770,32 @@ int update_block(struct f2fs_sb_info *sbi, void *buf, u32 *blkaddr,
 	struct seg_entry *se;
 	struct f2fs_summary sum;
 	u64 new_blkaddr, old_blkaddr = *blkaddr, offset;
-	int ret, type;
+	int ret, type, sum_type;
 
 	if (c.zoned_model != F2FS_ZONED_HM)
 		return dev_write_block(buf, old_blkaddr, WRITE_LIFE_NONE);
 
+	sum_type = get_sum_entry(sbi, old_blkaddr, &sum);
+
 	/* update sit bitmap & valid_blocks && se->type for old block*/
 	se = get_seg_entry(sbi, GET_SEGNO(sbi, old_blkaddr));
 	offset = OFFSET_IN_SEG(sbi, old_blkaddr);
 	type = se->type;
+	if (type < 0 || type >= NO_CHECK_TYPE) {
+		int fixed_type = (sum_type == SEG_TYPE_NODE ||
+				sum_type == SEG_TYPE_CUR_NODE) ?
+				CURSEG_HOT_NODE : CURSEG_HOT_DATA;
+
+		ASSERT_MSG("Invalid SIT segment type %d at blkaddr 0x%"PRIx64,
+				type, old_blkaddr);
+
+		if (!c.fix_on)
+			return -EINVAL;
+
+		FIX_MSG("Correct invalid segment type %d -> %d for blkaddr 0x%"PRIx64"\n",
+				type, fixed_type, old_blkaddr);
+		se->type = type = fixed_type;
+	}
 	se->valid_blocks--;
 	f2fs_clear_bit(offset, (char *)se->cur_valid_map);
 	if (need_fsync_data_record(sbi))
@@ -811,7 +828,6 @@ int update_block(struct f2fs_sb_info *sbi, void *buf, u32 *blkaddr,
 	f2fs_set_sit_bitmap(sbi, new_blkaddr);
 
 	/* update SSA */
-	get_sum_entry(sbi, old_blkaddr, &sum);
 	update_sum_entry(sbi, new_blkaddr, &sum);
 
 	if (IS_DATASEG(type)) {
-- 
2.55.0.571.g244d577d93-goog

Re: [f2fs-dev] [PATCH v3] fsck.f2fs: sanitize invalid segment type during block update

[Chao Yu]

On 8/5/26 01:18, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@google.com>
> 
> If an invalid segment type (type < 0 || type >= NO_CHECK_TYPE) is read
> from SIT during block update, update_block() now validates the type,
> reports corruption via ASSERT_MSG(), fixes se->type directly, and falls
> back to a valid active curseg type based on its SSA summary block type
> when fix_on is enabled. find_next_free_block() also validates want_type to
> prevent out-of-bounds accesses.
> 
> Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,