nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm()

Summary

In the Linux kernel, the following vulnerability has been resolved: nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm() nfc_llcp_recv_dm() handles DM(NOBOUND)/DM(REJ) for a socket that is still linked on local->connecting_sockets: it looks the socket up with nfc_llcp_connecting_sock_get(), sets sk->sk_state = LLCP_CLOSED and returns, without taking the socket lock and without unlinking the socket from the connecting_sockets list. llcp_sock_release() selects the list to unlink from by sk_state: a socket in LLCP_CONNECTING is unlinked from connecting_sockets, otherwise from the sockets list. Because recv_dm left the socket physically on connecting_sockets but in the LLCP_CLOSED state, release() takes the else branch and calls nfc_llcp_sock_unlink(&local->sockets, sk). That runs sk_del_node_init() while holding sockets.lock, i.e. it removes the socket from the connecting_sockets hlist under the wrong lock. A concurrent connect() linking another socket onto connecting_sockets under connecting_sockets.lock then mutates the same hlist unserialized, which corrupts the list and desyncs the sk_add_node()/sk_del_node_init() sock_hold()/__sock_put() pairing. An unprivileged local process holding LLCP sockets, with the DM supplied by the remote peer over an established LLCP link, can drive this to leak kernel sockets without bound (the mis-decrement goes through the non-freeing __sock_put() path, so the object is never released), leading to memory exhaustion / DoS. This is the same class of bug that was fixed in the sibling handler nfc_llcp_recv_cc() by commit b493ea2765cc ("nfc: llcp: Fix use-after-free race in nfc_llcp_recv_cc()"); recv_dm did not receive the equivalent fix. Fix it the same way: take lock_sock(), re-check that the socket is still hashed (release() may have won the race), and for the NOBOUND/REJ case unlink it from connecting_sockets before moving it to LLCP_CLOSED. The unlink drops the connecting_sockets membership reference via sk_del_node_init(), leaving the socket unhashed, so the later nfc_llcp_sock_unlink() in llcp_sock_release() becomes a no-op and no double put occurs.

Timeline

1. Oct 18, 2026, 3:18 PM UTCCVE published
2. Oct 19, 2026, 9:22 AM UTCRecord last updated

Affected versions

• Linux Linux

  From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in dd2d24add86b3b63cd87cf2feff98ae119ba19a6; From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in 812731dd8511f5768f4ff279b3c18d85cd21da4b; From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in dba1d9c7134afcb4b1bfad8c1b1b3f0ab5189b08; From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in c1e9ed52a6697354366dddf190fbacee8ed2f7c5; From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in 7fb2c0eeb79bfad64065f539a453138abd0edda6; From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in b94cf09720543cc34256c7aa88f8059cbe7c0419; From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in 320a2ff49bdce3f9a437b9a9ff341ff27d3bdbf1; From a69f32af86e389dd232b1bb2269e202c1bfcc60f · fixed in bf1460acdf8cf5a07c819f59785d40f20d113099

• Linux Linux

  3.6

• KernelLinux

  From 3.6.0 · fixed in 5.10.271; From 5.11.0 · fixed in 5.15.222; From 5.16.0 · fixed in 6.1.189; From 6.2.0 · fixed in 6.6.158; From 6.7.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.55; From 6.19.0 · fixed in 7.2.9

References 8