[PATCH] f2fs: limit recovery filename logging to stored length

[Wenjie Qi]

F2FS stores recovery filenames as a length plus a fixed-size i_name
buffer.  The buffer is not NUL-terminated, but recover_inode() and
recover_dentry() print it with %s.

For a 255-byte filename, recovery logging can read past i_name into the
following raw inode fields.

Print the name with a precision bounded by i_namelen and F2FS_NAME_LEN.

Fixes: f356fe0cba0e ("f2fs: add debug msgs in the recovery routine")
Cc: stable@xxxxxxxxxx
Assisted-by: Codex:gpt-5.5
Signed-off-by: Wenjie Qi <qiwenjie@xxxxxxxxxx>
---
 fs/f2fs/recovery.c | 41 +++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 89af8407b667..3fecfdbd5958 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -158,6 +158,22 @@ static int init_recovered_filename(const struct inode *dir,
 	return 0;
 }
 
+static const char *recover_printable_name(struct inode *inode,
+					  struct f2fs_inode *raw,
+					  int *name_len)
+{
+	static const char encrypted_name[] = "<encrypted>";
+
+	if (file_enc_name(inode)) {
+		*name_len = sizeof(encrypted_name) - 1;
+		return encrypted_name;
+	}
+
+	*name_len = min_t(unsigned int, le32_to_cpu(raw->i_namelen),
+			  F2FS_NAME_LEN);
+	return raw->i_name;
+}
+
 static int recover_dentry(struct inode *inode, struct folio *ifolio,
 						struct list_head *dir_list)
 {
@@ -170,7 +186,8 @@ static int recover_dentry(struct inode *inode, struct folio *ifolio,
 	struct inode *dir, *einode;
 	struct fsync_inode_entry *entry;
 	int err = 0;
-	char *name;
+	const char *name;
+	int name_len;
 
 	entry = get_fsync_inode(dir_list, pino);
 	if (!entry) {
@@ -229,12 +246,9 @@ static int recover_dentry(struct inode *inode, struct folio *ifolio,
 out_put:
 	f2fs_folio_put(folio, false);
 out:
-	if (file_enc_name(inode))
-		name = "<encrypted>";
-	else
-		name = raw_inode->i_name;
-	f2fs_notice(F2FS_I_SB(inode), "%s: ino = %x, name = %s, dir = %llu, err = %d",
-		    __func__, ino_of_node(ifolio), name,
+	name = recover_printable_name(inode, raw_inode, &name_len);
+	f2fs_notice(F2FS_I_SB(inode), "%s: ino = %x, name = %.*s, dir = %llu, err = %d",
+		    __func__, ino_of_node(ifolio), name_len, name,
 		    IS_ERR(dir) ? 0 : dir->i_ino, err);
 	return err;
 }
@@ -282,7 +296,8 @@ static int recover_inode(struct inode *inode, struct folio *folio)
 {
 	struct f2fs_inode *raw = F2FS_INODE(folio);
 	struct f2fs_inode_info *fi = F2FS_I(inode);
-	char *name;
+	const char *name;
+	int name_len;
 	int err;
 
 	inode->i_mode = le16_to_cpu(raw->i_mode);
@@ -331,13 +346,11 @@ static int recover_inode(struct inode *inode, struct folio *folio)
 
 	f2fs_mark_inode_dirty_sync(inode, true);
 
-	if (file_enc_name(inode))
-		name = "<encrypted>";
-	else
-		name = F2FS_INODE(folio)->i_name;
+	name = recover_printable_name(inode, raw, &name_len);
 
-	f2fs_notice(F2FS_I_SB(inode), "recover_inode: ino = %x, name = %s, inline = %x",
-		    ino_of_node(folio), name, raw->i_inline);
+	f2fs_notice(F2FS_I_SB(inode), "%s: ino = %x, name = %.*s, inline = %x",
+		    __func__, ino_of_node(folio), name_len, name,
+		    raw->i_inline);
 	return 0;
 }
 
-- 
2.43.0