fs/ntfs3: Sequential field availability check in mi_enum_attr()

The code is slightly reformatted to consistently check field availability
without duplication.

Fixes: 556bdf27c2dd ("ntfs3: Add bounds checking to mi_enum_attr()")
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

diff --git a/fs/ntfs3/record.c b/fs/ntfs3/record.c
index 427c71be0f087bf8365138903dbccffbef9335b4..f810f0419d25ea130fd9c01100f9f6258faa5108 100644 (file)
--- a/fs/ntfs3/record.c
+++ b/fs/ntfs3/record.c
@@ -237,6 +237,7 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
        }
 
        /* Can we use the first field (attr->type). */
+       /* NOTE: this code also checks attr->size availability. */
        if (off + 8 > used) {
                static_assert(ALIGN(sizeof(enum ATTR_TYPE), 8) == 8);
                return NULL;
@@ -257,10 +258,6 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
                return NULL;
 
        asize = le32_to_cpu(attr->size);
-       if (asize < SIZEOF_RESIDENT) {
-               /* Impossible 'cause we should not return such attribute. */
-               return NULL;
-       }
 
        /* Check overflow and boundary. */
        if (off + asize < off || off + asize > used)
@@ -290,6 +287,10 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
        if (attr->non_res != 1)
                return NULL;
 
+       /* Can we use memory including attr->nres.valid_size? */
+       if (asize < SIZEOF_NONRESIDENT)
+               return NULL;
+
        t16 = le16_to_cpu(attr->nres.run_off);
        if (t16 > asize)
                return NULL;
@@ -316,7 +317,8 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
 
        if (!attr->nres.svcn && is_attr_ext(attr)) {
                /* First segment of sparse/compressed attribute */
-               if (asize + 8 < SIZEOF_NONRESIDENT_EX)
+               /* Can we use memory including attr->nres.total_size? */
+               if (asize < SIZEOF_NONRESIDENT_EX)
                        return NULL;
 
                tot_size = le64_to_cpu(attr->nres.total_size);
@@ -326,9 +328,6 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
                if (tot_size > alloc_size)
                        return NULL;
        } else {
-               if (asize + 8 < SIZEOF_NONRESIDENT)
-                       return NULL;
-
                if (attr->nres.c_unit)
                        return NULL;