Vulnerability details

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: RFCOMM: hold listener socket in rfcomm_connect_ind() rfcomm_get_sock_by_channel() scans rfcomm_sk_list under the list lock, but returns the selected listener after dropping that lock without taking a reference. rfcomm_connect_ind() then locks the listener, queues a child socket on it, and may notify it after unlocking it. The buggy scenario involves two paths, with each column showing the order within that path: rfcomm_connect_ind(): listener close: 1. Find parent in 1. close() enters rfcomm_get_sock_by_channel() rfcomm_sock_release(). 2. Drop rfcomm_sk_list.lock 2. rfcomm_sock_shutdown() without pinning parent. closes the listener. 3. Call lock_sock(parent) and 3. rfcomm_sock_kill() bt_accept_enqueue(parent, unlinks and puts parent. sk, true). 4. Read parent flags and may 4. parent can be freed. call sk_state_change(). If close wins the race, parent can be freed before rfcomm_connect_ind() reaches lock_sock(), bt_accept_enqueue(), or the deferred-setup callback. Take a reference on the listener before leaving rfcomm_sk_list.lock. After lock_sock() succeeds, recheck that it is still in BT_LISTEN before queueing a child, cache the deferred-setup bit while the parent is locked, and drop the reference after the last parent use. KASAN reported a slab-use-after-free in lock_sock_nested() from rfcomm_connect_ind(), with the freeing stack going through rfcomm_sock_kill() and rfcomm_sock_release().

• https://git.kernel.org/stable/c/f5ec76bdbeb80f75ad0be204371afffee0f8fac8
• https://git.kernel.org/stable/c/a07d741c077d4e34b16458241a94d29039386553
• https://git.kernel.org/stable/c/1f73f92f66251065a5f39b09a47cf05ea14d3107
• https://git.kernel.org/stable/c/de31973ef00e5aa55496f84cf6a44bb157a34e02
• https://git.kernel.org/stable/c/b0e33e409715c617e2a20f46f99aa5403a14dfda
• https://git.kernel.org/stable/c/8802413ce63175fb522a2bd609fb043a3550c720
• https://git.kernel.org/stable/c/6f4462d12133106460d7c046b95aad2491e3fddf
• https://git.kernel.org/stable/c/43c441edacf953b39517a44f5e5e10a93618b226
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html