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Subject[PATCH 6/26] NTFS 2.1.22 - Bug and race fixes and improved error handling.
Date
This is patch 6/26 in the series.  It contains the following ChangeSet:

<aia21@cantab.net> (04/10/25 1.2026.1.22)
NTFS: Add attribute definition handling helpers to fs/ntfs/attrib.[hc]:
ntfs_attr_size_bounds_check(), ntfs_attr_can_be_non_resident(), and
ntfs_attr_can_be_resident(), which in turn use the new private helper
ntfs_attr_find_in_attrdef().

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

Best regards,

Anton
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/, http://www-stu.christs.cam.ac.uk/~aia21/

===================================================================

diff -Nru a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
--- a/fs/ntfs/ChangeLog 2004-11-10 13:44:36 +00:00
+++ b/fs/ntfs/ChangeLog 2004-11-10 13:44:36 +00:00
@@ -31,6 +31,10 @@
fs/ntfs/inode.c::ntfs_truncate() to set and clear it appropriately.
- Fix min_size and max_size definitions in ATTR_DEF structure in
fs/ntfs/layout.h to be signed.
+ - Add attribute definition handling helpers to fs/ntfs/attrib.[hc]:
+ ntfs_attr_size_bounds_check(), ntfs_attr_can_be_non_resident(), and
+ ntfs_attr_can_be_resident(), which in turn use the new private helper
+ ntfs_attr_find_in_attrdef().

2.1.21 - Fix some races and bugs, rewrite mft write code, add mft allocator.

diff -Nru a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
--- a/fs/ntfs/attrib.c 2004-11-10 13:44:36 +00:00
+++ b/fs/ntfs/attrib.c 2004-11-10 13:44:36 +00:00
@@ -24,8 +24,10 @@

#include "attrib.h"
#include "debug.h"
+#include "layout.h"
#include "mft.h"
#include "ntfs.h"
+#include "types.h"

/**
* ntfs_map_runlist - map (a part of) a runlist of an ntfs inode
@@ -947,6 +949,133 @@
unmap_extent_mft_record(ctx->ntfs_ino);
kmem_cache_free(ntfs_attr_ctx_cache, ctx);
return;
+}
+
+/**
+ * ntfs_attr_find_in_attrdef - find an attribute in the $AttrDef system file
+ * @vol: ntfs volume to which the attribute belongs
+ * @type: attribute type which to find
+ *
+ * Search for the attribute definition record corresponding to the attribute
+ * @type in the $AttrDef system file.
+ *
+ * Return the attribute type definition record if found and NULL if not found.
+ */
+static ATTR_DEF *ntfs_attr_find_in_attrdef(const ntfs_volume *vol,
+ const ATTR_TYPE type)
+{
+ ATTR_DEF *ad;
+
+ BUG_ON(!vol->attrdef);
+ BUG_ON(!type);
+ for (ad = vol->attrdef; (u8*)ad - (u8*)vol->attrdef <
+ vol->attrdef_size && ad->type; ++ad) {
+ /* We have not found it yet, carry on searching. */
+ if (likely(le32_to_cpu(ad->type) < le32_to_cpu(type)))
+ continue;
+ /* We found the attribute; return it. */
+ if (likely(ad->type == type))
+ return ad;
+ /* We have gone too far already. No point in continuing. */
+ break;
+ }
+ /* Attribute not found. */
+ ntfs_debug("Attribute type 0x%x not found in $AttrDef.",
+ le32_to_cpu(type));
+ return NULL;
+}
+
+/**
+ * ntfs_attr_size_bounds_check - check a size of an attribute type for validity
+ * @vol: ntfs volume to which the attribute belongs
+ * @type: attribute type which to check
+ * @size: size which to check
+ *
+ * Check whether the @size in bytes is valid for an attribute of @type on the
+ * ntfs volume @vol. This information is obtained from $AttrDef system file.
+ *
+ * Return 0 if valid, -ERANGE if not valid, or -ENOENT if the attribute is not
+ * listed in $AttrDef.
+ */
+int ntfs_attr_size_bounds_check(const ntfs_volume *vol, const ATTR_TYPE type,
+ const s64 size)
+{
+ ATTR_DEF *ad;
+
+ BUG_ON(size < 0);
+ /*
+ * $ATTRIBUTE_LIST has a maximum size of 256kiB, but this is not
+ * listed in $AttrDef.
+ */
+ if (unlikely(type == AT_ATTRIBUTE_LIST && size > 256 * 1024))
+ return -ERANGE;
+ /* Get the $AttrDef entry for the attribute @type. */
+ ad = ntfs_attr_find_in_attrdef(vol, type);
+ if (unlikely(!ad))
+ return -ENOENT;
+ /* Do the bounds check. */
+ if (((sle64_to_cpu(ad->min_size) > 0) &&
+ size < sle64_to_cpu(ad->min_size)) ||
+ ((sle64_to_cpu(ad->max_size) > 0) && size >
+ sle64_to_cpu(ad->max_size)))
+ return -ERANGE;
+ return 0;
+}
+
+/**
+ * ntfs_attr_can_be_non_resident - check if an attribute can be non-resident
+ * @vol: ntfs volume to which the attribute belongs
+ * @type: attribute type which to check
+ *
+ * Check whether the attribute of @type on the ntfs volume @vol is allowed to
+ * be non-resident. This information is obtained from $AttrDef system file.
+ *
+ * Return 0 if the attribute is allowed to be non-resident, -EPERM if not, or
+ * -ENOENT if the attribute is not listed in $AttrDef.
+ */
+int ntfs_attr_can_be_non_resident(const ntfs_volume *vol, const ATTR_TYPE type)
+{
+ ATTR_DEF *ad;
+
+ /*
+ * $DATA is always allowed to be non-resident even if $AttrDef does not
+ * specify this in the flags of the $DATA attribute definition record.
+ */
+ if (type == AT_DATA)
+ return 0;
+ /* Find the attribute definition record in $AttrDef. */
+ ad = ntfs_attr_find_in_attrdef(vol, type);
+ if (unlikely(!ad))
+ return -ENOENT;
+ /* Check the flags and return the result. */
+ if (ad->flags & CAN_BE_NON_RESIDENT)
+ return 0;
+ return -EPERM;
+}
+
+/**
+ * ntfs_attr_can_be_resident - check if an attribute can be resident
+ * @vol: ntfs volume to which the attribute belongs
+ * @type: attribute type which to check
+ *
+ * Check whether the attribute of @type on the ntfs volume @vol is allowed to
+ * be resident. This information is derived from our ntfs knowledge and may
+ * not be completely accurate, especially when user defined attributes are
+ * present. Basically we allow everything to be resident except for index
+ * allocation and $EA attributes.
+ *
+ * Return 0 if the attribute is allowed to be non-resident and -EPERM if not.
+ *
+ * Warning: In the system file $MFT the attribute $Bitmap must be non-resident
+ * otherwise windows will not boot (blue screen of death)! We cannot
+ * check for this here as we do not know which inode's $Bitmap is
+ * being asked about so the caller needs to special case this.
+ */
+int ntfs_attr_can_be_resident(const ntfs_volume *vol, const ATTR_TYPE type)
+{
+ if (type != AT_INDEX_ALLOCATION && type != AT_EA)
+ return 0;
+ return -EPERM;
}

/**
diff -Nru a/fs/ntfs/attrib.h b/fs/ntfs/attrib.h
--- a/fs/ntfs/attrib.h 2004-11-10 13:44:36 +00:00
+++ b/fs/ntfs/attrib.h 2004-11-10 13:44:36 +00:00
@@ -29,6 +29,7 @@
#include "layout.h"
#include "inode.h"
#include "runlist.h"
+#include "volume.h"

/**
* ntfs_attr_search_ctx - used in attribute search functions
@@ -83,6 +84,13 @@
extern ntfs_attr_search_ctx *ntfs_attr_get_search_ctx(ntfs_inode *ni,
MFT_RECORD *mrec);
extern void ntfs_attr_put_search_ctx(ntfs_attr_search_ctx *ctx);
+
+extern int ntfs_attr_size_bounds_check(const ntfs_volume *vol,
+ const ATTR_TYPE type, const s64 size);
+extern int ntfs_attr_can_be_non_resident(const ntfs_volume *vol,
+ const ATTR_TYPE type);
+extern int ntfs_attr_can_be_resident(const ntfs_volume *vol,
+ const ATTR_TYPE type);

extern int ntfs_attr_record_resize(MFT_RECORD *m, ATTR_RECORD *a, u32 new_size);

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