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tar: don't cross struct member boundaries with OLDGNU_MAGIC

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* src/create.c (write_gnu_long_link, start_header): Access
header->buffer + offsetof (struct posix_header, magic), instead of
header->header.magic, when reading or writing the OLDGNU_MAGIC
pattern.  The code violates the C standard without this change,
and GCC warns about this if fortify checking is enabled.  It's not
a bug on traditional (i.e., non-debugging) platforms, but it does
violate the C standard so it should be fixed.  Problem originally
reported by John Emil Karlson in
<http://lists.gnu.org/archive/html/bug-tar/2010-04/msg00023.html>.
* src/list.c (decode_header): Likewise.
This commit is contained in:
Paul Eggert
2010-10-27 22:25:18 -07:00
parent 3fe59ed5ef
commit b8feb2b142
2 changed files with 8 additions and 4 deletions
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6
src/create.c
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@@ -562,7 +562,8 @@ write_gnu_long_link (struct tar_stat_info *st, const char *p, char type)
GNAME_TO_CHARS (tmpname, header->header.gname);
free (tmpname);
strcpy (header->header.magic, OLDGNU_MAGIC);
strcpy (header->buffer + offsetof (struct posix_header, magic),
OLDGNU_MAGIC);
header->header.typeflag = type;
finish_header (st, header, -1);
@@ -899,7 +900,8 @@ start_header (struct tar_stat_info *st)
case OLDGNU_FORMAT:
case GNU_FORMAT: /*FIXME?*/
/* Overwrite header->header.magic and header.version in one blow. */
strcpy (header->header.magic, OLDGNU_MAGIC);
strcpy (header->buffer + offsetof (struct posix_header, magic),
OLDGNU_MAGIC);
break;
case POSIX_FORMAT:

6
src/list.c
View File

@@ -122,7 +122,7 @@ transform_stat_info (int typeflag, struct tar_stat_info *stat_info)
if (typeflag == GNUTYPE_VOLHDR)
/* Name transformations don't apply to volume headers. */
return;
transform_member_name (&stat_info->file_name, XFORM_REGFILE);
switch (typeflag)
{
@@ -592,7 +592,9 @@ decode_header (union block *header, struct tar_stat_info *stat_info,
else
format = USTAR_FORMAT;
}
else if (strcmp (header->header.magic, OLDGNU_MAGIC) == 0)
else if (strcmp (header->buffer + offsetof (struct posix_header, magic),
OLDGNU_MAGIC)
== 0)
format = hbits ? OLDGNU_FORMAT : GNU_FORMAT;
else
format = V7_FORMAT;