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xdgmime: Handle buggy type definitions with circular inheritance

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This fixes a stack overflow reported by a user who had both the
definition of text/javascript from shared-mime-info 2.3 and the
definition of text/javascript from shared-mime-info 2.4 installed at the
same time. In 2.3, text/javascript is a subtype of
application/ecmascript, but in 2.4 application/ecmascript is a subtype
of text/javascript. Having both at the same time resulted in circular
inheritance.

The new logic keeps a list of all parents that have already been
checked, which is more comprehensive than the old workaround that was
implemented in commit 38869ece2 ("xdgmime: Prevent infinite loops from
badly-formed MIME registrations").

https://bugs.archlinux.org/task/80279
This commit is contained in:
Alex Henrie
2023-11-19 15:54:27 -07:00
parent 09b728b2da
commit d9c50cac5d
4 changed files with 74 additions and 22 deletions
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47
gio/xdgmime/xdgmimecache.c
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@@ -751,8 +751,8 @@ cache_get_mime_type_for_data (const void *data,
/* Pick glob-result R where mime_type inherits from R */
for (n = 0; n < n_mime_types; n++)
{
if (mime_types[n] && _xdg_mime_cache_mime_type_subclass(mime_types[n], mime_type))
return mime_types[n];
if (mime_types[n] && _xdg_mime_cache_mime_type_subclass (mime_types[n], mime_type, NULL))
return mime_types[n];
}
if (n == 0)
{
@@ -901,13 +901,14 @@ is_super_type (const char *mime)
int
_xdg_mime_cache_mime_type_subclass (const char *mime,
const char *base)
const char *base,
const char **seen)
{
const char *umime, *ubase;
const char *umime, *ubase, *parent;
xdg_uint32_t j;
int i, min, max, med, cmp;
int i, k, min, max, med, cmp, first_seen = 0, ret = 0;
umime = _xdg_mime_cache_unalias_mime_type (mime);
ubase = _xdg_mime_cache_unalias_mime_type (base);
@@ -932,7 +933,13 @@ _xdg_mime_cache_mime_type_subclass (const char *mime,
if (strcmp (ubase, "application/octet-stream") == 0 &&
strncmp (umime, "inode/", 6) != 0)
return 1;
if (!seen)
{
seen = calloc (1, sizeof (char *));
first_seen = 1;
}
for (i = 0; _caches[i]; i++)
{
XdgMimeCache *cache = _caches[i];
@@ -966,10 +973,23 @@ _xdg_mime_cache_mime_type_subclass (const char *mime,
for (j = 0; j < n_parents; j++)
{
parent_offset = GET_UINT32 (cache->buffer, offset + 4 + 4 * j);
if (strcmp (cache->buffer + parent_offset, mime) != 0 &&
strcmp (cache->buffer + parent_offset, umime) != 0 &&
_xdg_mime_cache_mime_type_subclass (cache->buffer + parent_offset, ubase))
return 1;
parent = cache->buffer + parent_offset;
/* Detect and avoid buggy circular relationships */
for (k = 0; seen[k] != NULL; k++)
if (parent == seen[k])
goto next_parent;
seen = realloc (seen, (k + 2) * sizeof (char *));
seen[k] = parent;
seen[k + 1] = NULL;
if (_xdg_mime_cache_mime_type_subclass (parent, ubase, seen))
{
ret = 1;
goto done;
}
next_parent:
}
break;
@@ -977,7 +997,10 @@ _xdg_mime_cache_mime_type_subclass (const char *mime,
}
}
return 0;
done:
if (first_seen)
free (seen);
return ret;
}
const char *