CVE-2026-98581: nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm()
In the Linux kernel, the following vulnerability has been resolved:
nfc: llcp: Fix list corruption / refcount desync in nfcllcprecvdm()
nfcllcprecvdm() handles DM(NOBOUND)/DM(REJ) for a socket that is still linked on local->connectingsockets: it looks the socket up with nfcllcpconnectingsockget(), sets sk->skstate = LLCPCLOSED and returns, without taking the socket lock and without unlinking the socket from the connectingsockets list.
llcpsockrelease() selects the list to unlink from by skstate: a socket in LLCPCONNECTING is unlinked from connectingsockets, otherwise from the sockets list. Because recvdm left the socket physically on connectingsockets but in the LLCPCLOSED state, release() takes the else branch and calls nfcllcpsockunlink(&local->sockets, sk). That runs skdelnodeinit() while holding sockets.lock, i.e. it removes the socket from the connectingsockets hlist under the wrong lock. A concurrent connect() linking another socket onto connectingsockets under connectingsockets.lock then mutates the same hlist unserialized, which corrupts the list and desyncs the skaddnode()/skdelnodeinit() sockhold()/sockput() 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 sockput() 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 nfcllcprecvcc() by commit b493ea2765cc ("nfc: llcp: Fix use-after-free race in nfcllcprecvcc()"); recvdm did not receive the equivalent fix.
Fix it the same way: take locksock(), re-check that the socket is still hashed (release() may have won the race), and for the NOBOUND/REJ case unlink it from connectingsockets before moving it to LLCPCLOSED. The unlink drops the connectingsockets membership reference via skdelnodeinit(), leaving the socket unhashed, so the later nfcllcpsockunlink() in llcpsockrelease() becomes a no-op and no double put occurs.
Affected Software
Remediation
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In nfc_llcp_recv_dm(), take lock_sock(), re-check that the socket is still hashed, and for DM(NOBOUND)/DM(REJ) unlink it from connecting_sockets before setting sk_state to LLCP_CLOSED; perform the unlink under connecting_sockets.lock so the membership reference is dropped safely.
Event History
Frequently Asked Questions
What conditions are needed to trigger the corruption?
The affected path handles LLCP DM(NOBOUND) or DM(REJ) for a socket that remains linked on local->connecting_sockets. Corruption occurs when another connect operation concurrently adds a socket to that same connecting_sockets list while the first socket is released.
Which systems are in scope?
The issue is in the Linux kernel NFC LLCP socket handling path. The provided data does not state whether NFC LLCP is enabled or exposed in default kernel configurations.
What patch information is available?
The vulnerability is described as resolved, and the supplied references identify stable-tree commits dd2d24add86b3b63cd87cf2feff98ae119ba19a6, 812731dd8511f5768f4ff279b3c18d85cd21da4b, and dba1d9c7134afcb4b1bfad8c1b1b3f0ab5189b08. No fixed kernel version numbers are provided.