From: Johannes Berg johannes.berg@intel.com
commit 0f3b07f027f87a38ebe5c436490095df762819be upstream.
Rather than always iterating elements from frames with pure u8 pointers, add a type "struct element" that encapsulates the id/datalen/data format of them.
Then, add the element iteration macros * for_each_element * for_each_element_id * for_each_element_extid
which take, as their first 'argument', such a structure and iterate through a given u8 array interpreting it as elements.
While at it and since we'll need it, also add * for_each_subelement * for_each_subelement_id * for_each_subelement_extid
which instead of taking data/length just take an outer element and use its data/datalen.
Also add for_each_element_completed() to determine if any of the loops above completed, i.e. it was able to parse all of the elements successfully and no data remained.
Use for_each_element_id() in cfg80211_find_ie_match() as the first user of this.
Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/ieee80211.h | 53 ++++++++++++++++++++++++++++++++++++++++++++++ net/wireless/scan.c | 14 +++++------- 2 files changed, 59 insertions(+), 8 deletions(-)
--- a/include/linux/ieee80211.h +++ b/include/linux/ieee80211.h @@ -3185,4 +3185,57 @@ static inline bool ieee80211_action_cont return true; }
+struct element { + u8 id; + u8 datalen; + u8 data[]; +}; + +/* element iteration helpers */ +#define for_each_element(element, _data, _datalen) \ + for (element = (void *)(_data); \ + (u8 *)(_data) + (_datalen) - (u8 *)element >= \ + sizeof(*element) && \ + (u8 *)(_data) + (_datalen) - (u8 *)element >= \ + sizeof(*element) + element->datalen; \ + element = (void *)(element->data + element->datalen)) + +#define for_each_element_id(element, _id, data, datalen) \ + for_each_element(element, data, datalen) \ + if (element->id == (_id)) + +#define for_each_element_extid(element, extid, data, datalen) \ + for_each_element(element, data, datalen) \ + if (element->id == WLAN_EID_EXTENSION && \ + element->datalen > 0 && \ + element->data[0] == (extid)) + +#define for_each_subelement(sub, element) \ + for_each_element(sub, (element)->data, (element)->datalen) + +#define for_each_subelement_id(sub, id, element) \ + for_each_element_id(sub, id, (element)->data, (element)->datalen) + +#define for_each_subelement_extid(sub, extid, element) \ + for_each_element_extid(sub, extid, (element)->data, (element)->datalen) + +/** + * for_each_element_completed - determine if element parsing consumed all data + * @element: element pointer after for_each_element() or friends + * @data: same data pointer as passed to for_each_element() or friends + * @datalen: same data length as passed to for_each_element() or friends + * + * This function returns %true if all the data was parsed or considered + * while walking the elements. Only use this if your for_each_element() + * loop cannot be broken out of, otherwise it always returns %false. + * + * If some data was malformed, this returns %false since the last parsed + * element will not fill the whole remaining data. + */ +static inline bool for_each_element_completed(const struct element *element, + const void *data, size_t datalen) +{ + return (u8 *)element == (u8 *)data + datalen; +} + #endif /* LINUX_IEEE80211_H */ --- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -484,6 +484,8 @@ const u8 *cfg80211_find_ie_match(u8 eid, const u8 *match, int match_len, int match_offset) { + const struct element *elem; + /* match_offset can't be smaller than 2, unless match_len is * zero, in which case match_offset must be zero as well. */ @@ -491,14 +493,10 @@ const u8 *cfg80211_find_ie_match(u8 eid, (!match_len && match_offset))) return NULL;
- while (len >= 2 && len >= ies[1] + 2) { - if ((ies[0] == eid) && - (ies[1] + 2 >= match_offset + match_len) && - !memcmp(ies + match_offset, match, match_len)) - return ies; - - len -= ies[1] + 2; - ies += ies[1] + 2; + for_each_element_id(elem, eid, ies, len) { + if (elem->datalen >= match_offset - 2 + match_len && + !memcmp(elem->data + match_offset - 2, match, match_len)) + return (void *)elem; }
return NULL;