ntfs: sanitize MFT references returned from ntfs_lookup_inode_by_name()

ntfs_lookup_inode_by_name() returns MFT references read from directory
index entries on disk. These values are untrusted, but the function can
currently return an error-marked MFT reference to its callers without
validating it.

Callers later decode lookup failures with MREF_ERR(). A crafted NTFS image
can set the MREF error bit while leaving the low bits as an arbitrary
value, causing callers to consume a bogus pseudo-errno instead of treating
the lookup result as corrupted on-disk metadata.

Fix this at the source by normalizing every error-marked MFT reference
returned from ntfs_lookup_inode_by_name() to ERR_MREF(-EIO). Apply this to
all four directory lookup return paths so every caller gets a validated
result without needing additional checks or an API change.

This keeps the sanitization in the common lookup helper, which is cleaner
than duplicating validation in each caller.

Fixes: 1e9ea7e04472 ("Revert "fs: Remove NTFS classic"")
Cc: stable@vger.kernel.org
Reported-by: Hongling Zeng <zenghongling@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/fs/ntfs/dir.c b/fs/ntfs/dir.c
index 4b6bd5f30c65..6fa9ae3377cb 100644
--- a/fs/ntfs/dir.c
+++ b/fs/ntfs/dir.c
@@ -23,6 +23,13 @@
 __le16 I30[5] = { cpu_to_le16('$'), cpu_to_le16('I'),
 		cpu_to_le16('3'),	cpu_to_le16('0'), 0 };
 
+static inline u64 ntfs_check_mref(u64 mref)
+{
+	if (IS_ERR_MREF(mref))
+		return ERR_MREF(-EIO);
+	return mref;
+}
+
 /*
  * ntfs_lookup_inode_by_name - find an inode in a directory given its name
  * @dir_ni:	ntfs inode of the directory in which to search for the name
@@ -178,7 +185,7 @@ found_it:
 			mref = le64_to_cpu(ie->data.dir.indexed_file);
 			ntfs_attr_put_search_ctx(ctx);
 			unmap_mft_record(dir_ni);
-			return mref;
+			return ntfs_check_mref(mref);
 		}
 		/*
 		 * For a case insensitive mount, we also perform a case
@@ -273,7 +280,7 @@ found_it:
 		if (name) {
 			ntfs_attr_put_search_ctx(ctx);
 			unmap_mft_record(dir_ni);
-			return name->mref;
+			return ntfs_check_mref(name->mref);
 		}
 		ntfs_debug("Entry not found.");
 		err = -ENOENT;
@@ -413,7 +420,7 @@ found_it2:
 			mref = le64_to_cpu(ie->data.dir.indexed_file);
 			kfree(kaddr);
 			iput(ia_vi);
-			return mref;
+			return ntfs_check_mref(mref);
 		}
 		/*
 		 * For a case insensitive mount, we also perform a case
@@ -538,7 +545,7 @@ found_it2:
 	if (name) {
 		kfree(kaddr);
 		iput(ia_vi);
-		return name->mref;
+		return ntfs_check_mref(name->mref);
 	}
 	ntfs_debug("Entry not found.");
 	err = -ENOENT;