[PATCH 5.15.y] f2fs: validate orphan inode entry count

[Sasha Levin <sashal@kernel.org>]

From: Wenjie Qi <qwjhust@gmail.com>

[ Upstream commit 846c499a65816d13f1186e3090e825e8bb8bcb8b ]

f2fs_recover_orphan_inodes() trusts the orphan block entry_count when
replaying orphan inodes from the checkpoint pack. A corrupted entry_count
larger than F2FS_ORPHANS_PER_BLOCK makes the recovery loop read past the
ino[] array and interpret footer or following data as inode numbers.

On a crafted image, mounting an unpatched kernel can drive orphan recovery
into f2fs_bug_on() and panic the kernel. Validate entry_count before
consuming entries so corrupted checkpoint data fails the mount with
-EFSCORRUPTED and requests fsck instead.

Set ERROR_INCONSISTENT_ORPHAN as well, so the corruption reason can be
recorded in the superblock s_errors[] field. This gives fsck a persistent
hint even though mount-time orphan recovery failure may leave no chance to
persist SBI_NEED_FSCK through a checkpoint.

Cc: stable@kernel.org
Fixes: 127e670abfa7 ("f2fs: add checkpoint operations")
Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
[ Folio API ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/f2fs/checkpoint.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 71a3714419f850..29c372e421d02f 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -738,6 +738,7 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
 	for (i = 0; i < orphan_blocks; i++) {
 		struct page *page;
 		struct f2fs_orphan_block *orphan_blk;
+		unsigned int entry_count;
 
 		page = f2fs_get_meta_page(sbi, start_blk + i);
 		if (IS_ERR(page)) {
@@ -746,7 +747,17 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
 		}
 
 		orphan_blk = (struct f2fs_orphan_block *)page_address(page);
-		for (j = 0; j < le32_to_cpu(orphan_blk->entry_count); j++) {
+		entry_count = le32_to_cpu(orphan_blk->entry_count);
+		if (entry_count > F2FS_ORPHANS_PER_BLOCK) {
+			f2fs_err(sbi, "invalid orphan inode entry count %u",
+				 entry_count);
+			set_sbi_flag(sbi, SBI_NEED_FSCK);
+			err = -EFSCORRUPTED;
+			f2fs_put_page(page, 1);
+			goto out;
+		}
+
+		for (j = 0; j < entry_count; j++) {
 			nid_t ino = le32_to_cpu(orphan_blk->ino[j]);
 
 			err = recover_orphan_inode(sbi, ino);
-- 
2.53.0