wifi: mac80211: count only matching reservations in reserved switch

Overview

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

wifi: mac80211: count only matching reservations in reserved switch

ieee80211_vif_use_reserved_switch() validates a replacement by counting assigned links on ctx->replace_ctx and treating reservations too broadly. A link can still be assigned to the old channel context while holding a reservation that belongs to a different replacement operation.

That can make the current replacement appear complete too early. If another link finalizes first, the function can free the WILL_BE_REPLACED chanctx while the unmatched link and driver still use it, leading to a use-after-free in later beacon generation.

Require an in-place reservation to point at the current replacement context, and require the reserved and assigned contexts to be the matching replacement pair, before counting or moving the link.

Affected

• Linux >= 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f < d31f655e44631891788ca67018ec5e1ed1c7de86
• Linux >= 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f < 03525b632908b049f4d04cc8a71cdff2329589cf
• Linux >= 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f < 5cc54a000960bc88f8c58940164dca0e601ab39c
• Linux >= 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f < 437f3727b4fd715266c296435c116288f82666fd
• Linux 3.17

Remediation

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