[PATCH v2] ocfs2: reject inconsistent local xattr entries

[ZhengYuan Huang <gality369@gmail.com>]

[BUG]
A corrupt OCFS2 xattr entry can set OCFS2_XATTR_ENTRY_LOCAL while
keeping xe_value_size larger than OCFS2_XATTR_INLINE_SIZE. When that
entry reaches namevalue_size_xe(), the filesystem hits its BUG_ON:

kernel BUG at fs/ocfs2/xattr.c:231!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
RIP: 0010:namevalue_size_xe fs/ocfs2/xattr.c:231 [inline]
RIP: 0010:ocfs2_xa_block_wipe_namevalue+0x2e4/0x330 fs/ocfs2/xattr.c:1638
Call Trace:
 ocfs2_xa_wipe_namevalue fs/ocfs2/xattr.c:1470 [inline]
 ocfs2_xa_remove_entry+0xae/0x1d0 fs/ocfs2/xattr.c:1941
 ocfs2_xa_remove fs/ocfs2/xattr.c:2043 [inline]
 ocfs2_xa_set+0x11a8/0x30a0 fs/ocfs2/xattr.c:2247
 ocfs2_xattr_ibody_set+0x302/0xc50 fs/ocfs2/xattr.c:2795
 __ocfs2_xattr_set_handle+0x7e6/0xdb0 fs/ocfs2/xattr.c:3416
 ocfs2_xattr_set+0x1447/0x2610 fs/ocfs2/xattr.c:3650
 ocfs2_xattr_security_set+0x37/0x50 fs/ocfs2/xattr.c:7241
 __vfs_removexattr+0x14d/0x1d0 fs/xattr.c:518
 cap_inode_killpriv+0x29/0x50 security/commoncap.c:355
 security_inode_killpriv+0x105/0x220 security/security.c:2724
 setattr_prepare+0x147/0x8a0 fs/attr.c:219
 ocfs2_setattr+0x504/0x1fd0 fs/ocfs2/file.c:1148
 notify_change+0x4b5/0x1030 fs/attr.c:546
 do_truncate+0x1d2/0x230 fs/open.c:68
 handle_truncate fs/namei.c:3596 [inline]
 do_open fs/namei.c:3979 [inline]
 path_openat+0x260f/0x2ce0 fs/namei.c:4134
 do_filp_open+0x1f6/0x430 fs/namei.c:4161
 do_sys_openat2+0x117/0x1c0 fs/open.c:1437
 ...

[CAUSE]
namevalue_size_xe() assumes that local entries contain an inline value
no larger than OCFS2_XATTR_INLINE_SIZE. Existing xattr metadata
validation only checks whether the value fits the storage region, and
cached entries can reach lookup and bucket maintenance paths without a
semantic check. A corrupt entry can therefore be passed to
namevalue_size_xe().

[FIX]
Validate the local/value-size invariant in the existing flat and bucket
metadata validators and before accepting matched entries or traversing
bucket entries in paths that call namevalue_size_xe(). Return an OCFS2
corruption error instead of firing the assertion.

Signed-off-by: ZhengYuan Huang <gality369@gmail.com>
---
v2:
- Rebase onto the ACL lock-order fix in linux-next.
- Reuse the existing xattr metadata validators.
- Keep validation in cached lookup and bucket maintenance paths.
---
 fs/ocfs2/xattr.c | 53 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 7 deletions(-)

diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 35bcbb0ff607..e955126e4d7d 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -237,6 +237,21 @@ static int namevalue_size_xe(struct ocfs2_xattr_entry *xe)
 	return namevalue_size(xe->xe_name_len, value_len);
 }
 
+static int ocfs2_validate_xattr_entry(struct super_block *sb, u64 blkno,
+				      struct ocfs2_xattr_entry *xe)
+{
+	u64 value_len = le64_to_cpu(xe->xe_value_size);
+
+	if (value_len > OCFS2_XATTR_INLINE_SIZE &&
+	    ocfs2_xattr_is_local(xe))
+		return ocfs2_error(sb,
+				   "Invalid local xattr in block %llu: value size %llu\n",
+				   (unsigned long long)blkno,
+				   (unsigned long long)value_len);
+
+	return 0;
+}
+
 
 static int ocfs2_xattr_bucket_get_name_value(struct super_block *sb,
 					     struct ocfs2_xattr_header *xh,
@@ -992,7 +1007,7 @@ static int ocfs2_validate_xattr_entries_flat(struct super_block *sb, u64 blkno,
 	size_t entries_limit = region_size;
 	size_t nv_limit = region_size;
 	size_t max_entries;
-	int i;
+	int i, ret;
 
 	if (region_size < sizeof(*xh))
 		return ocfs2_error(sb,
@@ -1012,6 +1027,11 @@ static int ocfs2_validate_xattr_entries_flat(struct super_block *sb, u64 blkno,
 		struct ocfs2_xattr_entry *xe = &xh->xh_entries[i];
 		size_t name_offset = le16_to_cpu(xe->xe_name_offset);
 		size_t value_offset;
+		u64 value_len = le64_to_cpu(xe->xe_value_size);
+
+		ret = ocfs2_validate_xattr_entry(sb, blkno, xe);
+		if (ret)
+			return ret;
 
 		if (name_offset > nv_limit ||
 		    xe->xe_name_len > nv_limit - name_offset)
@@ -1026,8 +1046,7 @@ static int ocfs2_validate_xattr_entries_flat(struct super_block *sb, u64 blkno,
 					   (unsigned long long)blkno, i);
 
 		if (ocfs2_xattr_is_local(xe)) {
-			if (le64_to_cpu(xe->xe_value_size) >
-			    nv_limit - value_offset)
+			if (value_len > nv_limit - value_offset)
 				return ocfs2_error(sb,
 						   "Invalid xattr in block %llu: entry %d value is out of bounds\n",
 						   (unsigned long long)blkno,
@@ -1112,7 +1131,7 @@ static int ocfs2_validate_xattr_bucket(struct ocfs2_xattr_bucket *bucket,
 	size_t entries_limit = sb->s_blocksize;
 	size_t nv_limit = sb->s_blocksize;
 	size_t max_entries;
-	int i;
+	int i, ret;
 
 	if (region_size < sizeof(*xh))
 		return ocfs2_error(sb,
@@ -1140,6 +1159,11 @@ static int ocfs2_validate_xattr_bucket(struct ocfs2_xattr_bucket *bucket,
 		size_t block_off = name_offset >> sb->s_blocksize_bits;
 		size_t block_offset = name_offset % nv_limit;
 		size_t value_offset;
+		u64 value_len = le64_to_cpu(xe->xe_value_size);
+
+		ret = ocfs2_validate_xattr_entry(sb, blkno, xe);
+		if (ret)
+			return ret;
 
 		if (name_offset >= region_size || block_off >= bucket->bu_blocks)
 			return ocfs2_error(sb,
@@ -1158,8 +1182,7 @@ static int ocfs2_validate_xattr_bucket(struct ocfs2_xattr_bucket *bucket,
 					   (unsigned long long)blkno, i);
 
 		if (ocfs2_xattr_is_local(xe)) {
-			if (le64_to_cpu(xe->xe_value_size) >
-			    nv_limit - value_offset)
+			if (value_len > nv_limit - value_offset)
 				return ocfs2_error(sb,
 						   "Invalid xattr bucket %llu: entry %d value is out of bounds\n",
 						   (unsigned long long)blkno,
@@ -1307,7 +1330,7 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
 {
 	struct ocfs2_xattr_entry *entry;
 	size_t name_len;
-	int i, name_offset, cmp = 1;
+	int i, name_offset, cmp = 1, ret;
 
 	if (name == NULL)
 		return -EINVAL;
@@ -1330,6 +1353,12 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
 				return -EFSCORRUPTED;
 			}
 			cmp = memcmp(name, (xs->base + name_offset), name_len);
+			if (!cmp) {
+				ret = ocfs2_validate_xattr_entry(inode->i_sb,
+								 OCFS2_I(inode)->ip_blkno, entry);
+				if (ret)
+					return ret;
+			}
 		}
 		if (cmp == 0)
 			break;
@@ -4041,6 +4070,10 @@ static int ocfs2_find_xe_in_bucket(struct inode *inode,
 
 		xe_name = bucket_block(bucket, block_off) + new_offset;
 		if (!memcmp(name, xe_name, name_len)) {
+			ret = ocfs2_validate_xattr_entry(inode->i_sb,
+							 OCFS2_I(inode)->ip_blkno, xe);
+			if (ret)
+				break;
 			*xe_index = i;
 			*found = 1;
 			ret = 0;
@@ -4681,6 +4714,9 @@ static int ocfs2_defrag_xattr_bucket(struct inode *inode,
 	xe = xh->xh_entries;
 	end = OCFS2_XATTR_BUCKET_SIZE;
 	for (i = 0; i < le16_to_cpu(xh->xh_count); i++, xe++) {
+		ret = ocfs2_validate_xattr_entry(inode->i_sb, blkno, xe);
+		if (ret)
+			goto out;
 		offset = le16_to_cpu(xe->xe_name_offset);
 		len = namevalue_size_xe(xe);
 
@@ -4963,6 +4999,9 @@ static int ocfs2_divide_xattr_bucket(struct inode *inode,
 	name_value_len = 0;
 	for (i = 0; i < start; i++) {
 		xe = &xh->xh_entries[i];
+		ret = ocfs2_validate_xattr_entry(inode->i_sb, blk, xe);
+		if (ret)
+			goto out;
 		name_value_len += namevalue_size_xe(xe);
 		if (le16_to_cpu(xe->xe_name_offset) < name_offset)
 			name_offset = le16_to_cpu(xe->xe_name_offset);
-- 
2.43.0