[PATCH v2 02/10] ntfs: validate EA chains and link zero-terminated tails

[Baolin Liu <liubaolin12138@163.com>]

From: Baolin Liu <liubaolin@kylinos.cn>

A zero next-entry offset terminates an EA list. Appending an entry
without linking the old tail makes the new entry unreachable. Invalid
entries are also treated as missing names, allowing setters to proceed
on corrupt metadata.

Validate the entire chain before modifying it and connect a zero tail
to the append position. Check name terminators and retain the full tail
span when removing an entry. Return EUCLEAN for malformed EA structures
and inconsistent information lengths, preserving that error through the
get and set paths. Keep ENOENT for a missing name and translate it to
ENODATA only at the xattr read boundary. Preserve lower-level read errors.

Signed-off-by: Baolin Liu <liubaolin@kylinos.cn>
---
 fs/ntfs/ea.c | 49 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 14 deletions(-)

diff --git a/fs/ntfs/ea.c b/fs/ntfs/ea.c
index bb97df3045a0..59160e49a53f 100644
--- a/fs/ntfs/ea.c
+++ b/fs/ntfs/ea.c
@@ -53,10 +53,13 @@ static int ntfs_ea_lookup(char *ea_buf, s64 ea_buf_size, const char *name,
 	loff_t offset, p_ea_size;
 	unsigned int next;
 
+	if (!ea_buf_size)
+		return -ENOENT;
+
 	offset = 0;
 	do {
 		if (ea_buf_size - offset < sizeof(struct ea_attr))
-			break;
+			return -EUCLEAN;
 
 		p_ea = (const struct ea_attr *)&ea_buf[offset];
 		next = le32_to_cpu(p_ea->next_entry_offset);
@@ -64,31 +67,31 @@ static int ntfs_ea_lookup(char *ea_buf, s64 ea_buf_size, const char *name,
 
 		if (p_ea_size < sizeof(struct ea_attr) ||
 		    offset + p_ea_size > ea_buf_size)
-			break;
+			return -EUCLEAN;
 
 		if ((s64)p_ea->ea_name_length + 1 >
 		    p_ea_size - offsetof(struct ea_attr, ea_name))
-			break;
+			return -EUCLEAN;
 
 		actual_size = ALIGN(struct_size(p_ea, ea_name, 1 + p_ea->ea_name_length +
 					le16_to_cpu(p_ea->ea_value_length)), 4);
-		if (actual_size > p_ea_size)
-			break;
+		if (actual_size > p_ea_size ||
+		    p_ea->ea_name[p_ea->ea_name_length])
+			return -EUCLEAN;
 
-		if (p_ea->ea_name_length == name_len &&
+		if (name && p_ea->ea_name_length == name_len &&
 		    !memcmp(p_ea->ea_name, name, name_len)) {
 			*ea_offset = offset;
-			*ea_size = next ? next : actual_size;
+			*ea_size = p_ea_size;
 
 			if (ea_buf_size < *ea_offset + *ea_size)
-				goto out;
+				return -EUCLEAN;
 
 			return 0;
 		}
 		offset += next;
 	} while (next > 0 && offset < ea_buf_size);
 
-out:
 	return -ENOENT;
 }
 
@@ -126,7 +129,7 @@ static int ntfs_get_ea(struct inode *inode, const char *name, size_t name_len,
 		return PTR_ERR(p_ea_info);
 	if (ea_info_size != sizeof(struct ea_information)) {
 		kvfree(p_ea_info);
-		return -EIO;
+		return -EUCLEAN;
 	}
 
 	ea_info_qlen = le32_to_cpu(p_ea_info->ea_query_length);
@@ -137,7 +140,7 @@ static int ntfs_get_ea(struct inode *inode, const char *name, size_t name_len,
 		return PTR_ERR(ea_buf);
 
 	if (ea_info_qlen > all_ea_size) {
-		err = -EIO;
+		err = -EUCLEAN;
 		goto free_ea_buf;
 	}
 
@@ -162,7 +165,8 @@ static int ntfs_get_ea(struct inode *inode, const char *name, size_t name_len,
 		return ea_value_len;
 	}
 
-	err = -ENODATA;
+	if (err == -ENOENT)
+		err = -ENODATA;
 free_ea_buf:
 	kvfree(ea_buf);
 	return err;
@@ -216,7 +220,7 @@ static int ntfs_set_ea(struct inode *inode, const char *name, size_t name_len,
 			goto out;
 		}
 		if (ea_info_size != sizeof(struct ea_information)) {
-			err = -EIO;
+			err = -EUCLEAN;
 			goto out;
 		}
 
@@ -255,12 +259,29 @@ static int ntfs_set_ea(struct inode *inode, const char *name, size_t name_len,
 	}
 
 	if (ea_info_qsize > all_ea_size) {
-		err = -EIO;
+		err = -EUCLEAN;
 		goto out;
 	}
 
+	/* Validate the whole chain before modifying it, including its tail. */
+	err = ntfs_ea_lookup(ea_buf, ea_info_qsize, NULL, 0, &ea_off,
+			     &ea_size);
+	if (err != -ENOENT)
+		goto out;
+	/* A zero tail offset must be linked before appending another EA. */
+	for (ea_off = 0; ea_off < ea_info_qsize; ea_off += ea_size) {
+		p_ea = (struct ea_attr *)(ea_buf + ea_off);
+		ea_size = le32_to_cpu(p_ea->next_entry_offset);
+		if (!ea_size) {
+			ea_size = ea_info_qsize - ea_off;
+			p_ea->next_entry_offset = cpu_to_le32(ea_size);
+		}
+	}
+
 	err = ntfs_ea_lookup(ea_buf, ea_info_qsize, name, name_len, &ea_off,
 			&ea_size);
+	if (err && err != -ENOENT)
+		goto out;
 	if (ea_info_qsize && !err) {
 		if (flags & XATTR_CREATE) {
 			err = -EEXIST;
-- 
2.51.0