From: John Walker Date: Thu, 7 May 2026 23:07:20 +0000 (-0600) Subject: wifi: cfg80211: advance loop vars in cfg80211_merge_profile() X-Git-Tag: v7.1-rc5~40^2^2~10 X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=7666dbb1bacc4ba522b96740cba7283d243d16e1;p=thirdparty%2Fkernel%2Flinux.git wifi: cfg80211: advance loop vars in cfg80211_merge_profile() cfg80211_merge_profile() reassembles a Multi-BSSID non-transmitted BSS profile that has been split across multiple consecutive MBSSID elements. Its while-loop calls cfg80211_get_profile_continuation(ie, ielen, mbssid_elem, sub_elem) but never advances mbssid_elem or sub_elem inside the body. Each iteration therefore searches for a continuation that follows the same fixed pair; the helper returns the same next_mbssid; and the same next_sub bytes are memcpy()'d into merged_ie at a growing offset until the buffer fills. Advance both mbssid_elem and sub_elem to the just-consumed continuation so the next call to cfg80211_get_profile_continuation() searches for a further continuation beyond it (or returns NULL when none exists). A specially-crafted malicious beacon can take advantage of this bug to cause the kernel to spend an excessive amount of time in cfg80211_merge_profile (up to as much as 2ms per beacon received), which could theoretically be abused in some way. Cc: stable@vger.kernel.org Fixes: fe806e4992c9 ("cfg80211: support profile split between elements") Signed-off-by: John Walker Link: https://patch.msgid.link/20260507230720.64783-1-johnwalker0@gmail.com Signed-off-by: Johannes Berg --- diff --git a/net/wireless/scan.c b/net/wireless/scan.c index 328af43ef8325..358cbc9e43d85 100644 --- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -2462,6 +2462,9 @@ size_t cfg80211_merge_profile(const u8 *ie, size_t ielen, memcpy(merged_ie + copied_len, next_sub->data, next_sub->datalen); copied_len += next_sub->datalen; + + mbssid_elem = next_mbssid; + sub_elem = next_sub; } return copied_len;