linux-kernel - [PATCH] f2fs: fix to detect potential corrupted nid in free_nid

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Message-ID: <20250807024431.3805293-1-chao@kernel.org>
Date: Thu,  7 Aug 2025 10:44:31 +0800
From: Chao Yu <chao@...nel.org>
To: jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	Chao Yu <chao@...nel.org>
Subject: [PATCH] f2fs: fix to detect potential corrupted nid in free_nid_list

As reported, on-disk footer.ino and footer.nid is the same and
out-of-range, let's add sanity check on f2fs_alloc_nid() to detect
any potential corruption in free_nid_list.

Signed-off-by: Chao Yu <chao@...nel.org>
---
 fs/f2fs/node.c          | 17 ++++++++++++++++-
 include/linux/f2fs_fs.h |  1 +
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 27743b93e186..286e8a53f8e7 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -27,12 +27,17 @@ static struct kmem_cache *free_nid_slab;
 static struct kmem_cache *nat_entry_set_slab;
 static struct kmem_cache *fsync_node_entry_slab;
 
+static inline bool is_invalid_nid(struct f2fs_sb_info *sbi, nid_t nid)
+{
+	return nid < F2FS_ROOT_INO(sbi) || nid >= NM_I(sbi)->max_nid;
+}
+
 /*
  * Check whether the given nid is within node id range.
  */
 int f2fs_check_nid_range(struct f2fs_sb_info *sbi, nid_t nid)
 {
-	if (unlikely(nid < F2FS_ROOT_INO(sbi) || nid >= NM_I(sbi)->max_nid)) {
+	if (unlikely(is_invalid_nid(sbi, nid))) {
 		set_sbi_flag(sbi, SBI_NEED_FSCK);
 		f2fs_warn(sbi, "%s: out-of-range nid=%x, run fsck to fix.",
 			  __func__, nid);
@@ -2634,6 +2639,16 @@ bool f2fs_alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
 		f2fs_bug_on(sbi, list_empty(&nm_i->free_nid_list));
 		i = list_first_entry(&nm_i->free_nid_list,
 					struct free_nid, list);
+
+		if (unlikely(is_invalid_nid(sbi, i->nid))) {
+			spin_unlock(&nm_i->nid_list_lock);
+			f2fs_err(sbi, "Corrupted nid %u in free_nid_list",
+								i->nid);
+			f2fs_stop_checkpoint(sbi, false,
+					STOP_CP_REASON_CORRUPTED_NID);
+			return false;
+		}
+
 		*nid = i->nid;
 
 		__move_free_nid(sbi, i, FREE_NID, PREALLOC_NID);
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index 2f8b8bfc0e73..6afb4a13b81d 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -79,6 +79,7 @@ enum stop_cp_reason {
 	STOP_CP_REASON_FLUSH_FAIL,
 	STOP_CP_REASON_NO_SEGMENT,
 	STOP_CP_REASON_CORRUPTED_FREE_BITMAP,
+	STOP_CP_REASON_CORRUPTED_NID,
 	STOP_CP_REASON_MAX,
 };
 
-- 
2.49.0