From fb3136e8abe5fec9e8a749e5879b75c696f7ba0e Mon Sep 17 00:00:00 2001

From: "Richard W.M. Jones" <rjones@redhat.com>

Date: Thu, 12 Mar 2020 14:40:05 +0000

Subject: [PATCH] daemon: xattr: Filter out user.WofCompressedData from xattrs

 (RHBZ#1811539).

See comment in code for justification.

Thanks: Yongkui Guo for finding the bug.

(cherry picked from commit c2c11382bbeb4500f3388a31ffd08cfc18b0de40)

---

 daemon/xattr.c | 43 ++++++++++++++++++++++++++++++++++++++++---

 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/daemon/xattr.c b/daemon/xattr.c

index 3e1144963..43e49384f 100644

--- a/daemon/xattr.c

+++ b/daemon/xattr.c

@@ -19,6 +19,8 @@

 #include <config.h>

 #include <stdio.h>

+#include <stdlib.h>

+#include <stdbool.h>

 #include <limits.h>

 #include <unistd.h>

@@ -119,6 +121,29 @@ split_attr_names (char *buf, size_t len)

   return take_stringsbuf (&ret;;

 }

+/* We hide one extended attribute automatically.  This is used by NTFS

+ * to store the compressed contents of a file when using "CompactOS"

+ * (per-file compression).  I justify this by:

+ *

+ * (1) The attribute is only used internally by NTFS.  The actual file

+ * contents are still available.

+ *

+ * (2) It's probably not valid to copy this attribute when copying the

+ * other attributes of a file.  ntfs-3g-system-compression doesn't

+ * support writing compressed files.

+ *

+ * (3) This file isn't readable by the Linux kernel.  Reading it will

+ * always return -E2BIG (RHBZ#1811539).  So we can't read it even if

+ * we wanted to.

+ *

+ * (4) The Linux kernel itself hides other attributes.

+ */

+static bool

+not_hidden_xattr (const char *attrname)

+{

+  return STRNEQ (attrname, "user.WofCompressedData");

+}

+

 static int

 compare_xattrs (const void *vxa1, const void *vxa2)

 {

@@ -136,6 +161,7 @@ getxattrs (const char *path,

 {

   ssize_t len, vlen;

   CLEANUP_FREE char *buf = NULL;

+  CLEANUP_FREE /* not string list */ char **names_unfiltered = NULL;

   CLEANUP_FREE /* not string list */ char **names = NULL;

   size_t i;

   guestfs_int_xattr_list *r = NULL;

@@ -145,7 +171,10 @@ getxattrs (const char *path,

     /* _listxattrs issues reply_with_perror already. */

     goto error;

-  names = split_attr_names (buf, len);

+  names_unfiltered = split_attr_names (buf, len);

+  if (names_unfiltered == NULL)

+    goto error;

+  names = filter_list (not_hidden_xattr, names_unfiltered);

   if (names == NULL)

     goto error;

@@ -323,6 +352,7 @@ do_internal_lxattrlist (const char *path, char *const *names)

     void *newptr;

     CLEANUP_FREE char *pathname = NULL;

     CLEANUP_FREE char *buf = NULL;

+    CLEANUP_FREE /* not string list */ char **attrnames_unfiltered = NULL;

     CLEANUP_FREE /* not string list */ char **attrnames = NULL;

     /* Be careful in this loop about which errors cause the whole call

@@ -381,7 +411,10 @@ do_internal_lxattrlist (const char *path, char *const *names)

     if (len == -1)

       continue; /* not fatal */

-    attrnames = split_attr_names (buf, len);

+    attrnames_unfiltered = split_attr_names (buf, len);

+    if (attrnames_unfiltered == NULL)

+      goto error;

+    attrnames = filter_list (not_hidden_xattr, attrnames_unfiltered);

     if (attrnames == NULL)

       goto error;

     nr_attrs = guestfs_int_count_strings (attrnames);

@@ -539,6 +572,7 @@ copy_xattrs (const char *src, const char *dest)

 {

   ssize_t len, vlen, ret, attrval_len = 0;

   CLEANUP_FREE char *buf = NULL, *attrval = NULL;

+  CLEANUP_FREE /* not string list */ char **names_unfiltered = NULL;

   CLEANUP_FREE /* not string list */ char **names = NULL;

   size_t i;

@@ -547,7 +581,10 @@ copy_xattrs (const char *src, const char *dest)

     /* _listxattrs issues reply_with_perror already. */

     goto error;

-  names = split_attr_names (buf, len);

+  names_unfiltered = split_attr_names (buf, len);

+  if (names_unfiltered == NULL)

+    goto error;

+  names = filter_list (not_hidden_xattr, names_unfiltered);

   if (names == NULL)

     goto error;

-- 

2.18.4