Re: svn commit: r312391 - in head: share/man/man5 sys/ufs/ufs

[Conrad Meyer]

On Wed, Jan 18, 2017 at 9:55 AM, Conrad E. Meyer  wrote:
> Author: cem
> Date: Wed Jan 18 17:55:49 2017
> New Revision: 312391
> URL: https://svnweb.freebsd.org/changeset/base/312391
>
> Log:
>   ufs/extattr.h: Fix documentation of ea_name termination
>
>   The ea_name string is not nul-terminated.  Correct the documentation.
>
>   Because the subsequent field is padded to 8 bytes, and the padding is
>   zeroed, the ea_name string will appear to be nul-terminated whenever the
>   length isn't exactly one (mod eight).
>
>   This was introduced in r167010 (2007).
>
>   Additionally, mark the length fields as unsigned.  This particularly
>   matters for the single byte ea_namelength field, which can represent
>   extended attribute names up to 255 bytes long.
>
>   No functional change.

Whoops — very minor functional change — restore(8) can now handle some
dumps with extended attribute names longer than 127 characters that it
couldn't before, due to the unsigned type change called out above.

Best,
Conrad
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svn commit: r312391 - in head: share/man/man5 sys/ufs/ufs

[Conrad E. Meyer]

Author: cem
Date: Wed Jan 18 17:55:49 2017
New Revision: 312391
URL: https://svnweb.freebsd.org/changeset/base/312391

Log:
  ufs/extattr.h: Fix documentation of ea_name termination
  
  The ea_name string is not nul-terminated.  Correct the documentation.
  
  Because the subsequent field is padded to 8 bytes, and the padding is
  zeroed, the ea_name string will appear to be nul-terminated whenever the
  length isn't exactly one (mod eight).
  
  This was introduced in r167010 (2007).
  
  Additionally, mark the length fields as unsigned.  This particularly
  matters for the single byte ea_namelength field, which can represent
  extended attribute names up to 255 bytes long.
  
  No functional change.
  
  PR:   216127
  Reported by:  dewayne at heuristicsystems.com.au
  Reviewed by:  kib@
  Sponsored by: Dell EMC Isilon
  Differential Revision:https://reviews.freebsd.org/D9206

Modified:
  head/share/man/man5/fs.5
  head/sys/ufs/ufs/extattr.h

Modified: head/share/man/man5/fs.5
==
--- head/share/man/man5/fs.5Wed Jan 18 17:55:08 2017(r312390)
+++ head/share/man/man5/fs.5Wed Jan 18 17:55:49 2017(r312391)
@@ -28,7 +28,7 @@
 .\" @(#)fs.5   8.2 (Berkeley) 4/19/94
 .\" $FreeBSD$
 .\"
-.Dd April 23, 2016
+.Dd January 16, 2017
 .Dt FS 5
 .Os
 .Sh NAME
@@ -388,18 +388,19 @@ For further information, see the include
 The format of an external attribute is defined by the extattr structure:
 .Bd -literal
 struct extattr {
-   int32_t ea_length;  /* length of this attribute */
-   int8_t  ea_namespace;   /* name space of this attribute */
-   int8_t  ea_contentpadlen;   /* padding at end of attribute */
-   int8_t  ea_namelength;  /* length of attribute name */
-   charea_name[1]; /* null-terminated attribute name */
+   uint32_t ea_length; /* length of this attribute */
+   uint8_t ea_namespace;   /* name space of this attribute */
+   uint8_t ea_contentpadlen;   /* bytes of padding at end of attribute */
+   uint8_t ea_namelength;  /* length of attribute name */
+   charea_name[1]; /* attribute name (NOT nul-terminated) */
+   /* padding, if any, to align attribute content to 8 byte boundary */
/* extended attribute content follows */
 };
 .Ed
 .Pp
 Several macros are defined to manipulate these structures.
 Each macro takes a pointer to an extattr structure.
-.Bl -tag -width ".Dv EXTATTR_SET_LENGTHS(eap, size)"
+.Bl -tag -width ".Dv EXTATTR_CONTENT_SIZE(eap)"
 .It Dv EXTATTR_NEXT(eap)
 Returns a pointer to the next extended attribute following
 .Fa eap .
@@ -409,35 +410,19 @@ Returns a pointer to the extended attrib
 .It Dv EXTATTR_CONTENT_SIZE(eap)
 Returns the size of the extended attribute content referenced by
 .Fa eap .
-.It Dv EXTATTR_SET_LENGTHS(eap, size)
-Called with the size of the attribute content after initializing
-the attribute name to calculate and set the
-.Fa ea_length ,
-.Fa ea_namelength ,
-and
-.Fa ea_contentpadlen
-fields of the extended attribute structure.
 .El
 .Pp
 The following code identifies an ACL:
 .Bd -literal
if (eap->ea_namespace == EXTATTR_NAMESPACE_SYSTEM &&
-   !strcmp(eap->ea_name, POSIX1E_ACL_ACCESS_EXTATTR_NAME) {
+eap->ea_namelength == sizeof(POSIX1E_ACL_ACCESS_EXTATTR_NAME) - 1 
&&
+   strncmp(eap->ea_name, POSIX1E_ACL_ACCESS_EXTATTR_NAME,
+ sizeof(POSIX1E_ACL_ACCESS_EXTATTR_NAME) - 1) == 0) {
aclp = EXTATTR_CONTENT(eap);
acllen = EXTATTR_CONTENT_SIZE(eap);
...
}
 .Ed
-.Pp
-The following code creates an extended attribute
-containing a copy of a structure
-.Fa mygif :
-.Bd -literal
-   eap->ea_namespace = EXTATTR_NAMESPACE_USER;
-   strcpy(eap->ea_name, "filepic.gif");
-   EXTATTR_SET_LENGTHS(eap, sizeof(struct mygif));
-   memcpy(EXTATTR_CONTENT(eap), , sizeof(struct mygif));
-.Ed
 .Sh HISTORY
 A super-block structure named filsys appeared in
 .At v6 .

Modified: head/sys/ufs/ufs/extattr.h
==
--- head/sys/ufs/ufs/extattr.h  Wed Jan 18 17:55:08 2017(r312390)
+++ head/sys/ufs/ufs/extattr.h  Wed Jan 18 17:55:49 2017(r312391)
@@ -73,11 +73,12 @@ struct ufs_extattr_header {
  * This structure defines the required fields of an extended-attribute header.
  */
 struct extattr {
-   int32_t ea_length;  /* length of this attribute */
-   int8_t  ea_namespace;   /* name space of this attribute */
-   int8_t  ea_contentpadlen;   /* bytes of padding at end of attribute */
-   int8_t  ea_namelength;  /* length of attribute name */
-   charea_name[1]; /* null-terminated attribute name */
+   uint32_t ea_length; /* length of this attribute */
+   uint8_t ea_namespace;   /* name space