wifi: cfg80211: advance loop vars in cfg80211_merge_profile()

Overview

In the Linux kernel, the following vulnerability has been resolved:

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.

Affected

• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < 5817e1e5205498a5df66eba2b34e817f4210fd0f
• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < cedbb608494ba1e7a5c6c56b7f1d3fd470094f28
• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < c0bc4c8bd556cbe036a5b9ed333c0aab9aadfcb8
• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < 1ced0f5a851f9cae274545a42a06c459b7fd8881
• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < 67915715fd3874057457363c87c63e18829527df
• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < 6cfae4914439878b8acb35c7e3b40096eeb2ad9c
• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < 1343a480f84b80c1249133a90ef87f8751d65cbb
• Linux >= fe806e4992c9047affd263bcc13b2c047029a726 < 7666dbb1bacc4ba522b96740cba7283d243d16e1
• Linux 5.2

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.