From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A509A374A16; Wed, 30 Sep 2026 16:41:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790786484; cv=none; b=OPxD0H/40T4xEoXh6z/q4SBHMc4J957xR3AEcPPUDWXIy9HJ7Ff8/n9gK6hAnSksIRwCqdhwHwu0z3qX2A/uRBvMLkTEAWD/IsBoHlNmN8QDU8TlONJL61njlt+cN/YGPh2nSH8TYdCEfyoJXcnXatOnyMzSuCzFOxoeJFzxbjI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790786484; c=relaxed/simple; bh=ErufPBxW4FbVsFlwMLILwpQxrs1KcP0L7Wpvo0qTzrs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fUiww2/dnQ6xDwJre+MsSD1vo3AgLYNmVKJ1mxyZ+HhtexD1Oc/moeZ9Ls/aM2W0B9MVzWODXBizSMbcbRosQ0JOEP28Le3YDlZkL6SxzQC5o8ZEtMXzb2VzSqBGgC1RDynvCV6awoLJ47aw3X6Jq1GQmMnb+CSYsO/iA7D8M8I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=U2/MdmQX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="U2/MdmQX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C5871F000FF; Wed, 30 Sep 2026 16:41:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790786483; bh=Aqd+RdPktsmS0sAZibv0to5e4mCwuAxxr9ATHpXCrrg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=U2/MdmQXLHK00yvyQCfPSGegjiKhCzBTdMkj1jSiinVclvEw5wrXwyugZyxkWiPJ3 CAS/btquiQcprn13YsmErz1YOg2Lp7XMgucf1OfssDAjYGOEq4CM3f+UNaD0UA0hWE qA95SUImh6THj0sO+AWC8qfW77kgDI1ddfMtAL4Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Aldo Ariel Panzardo , David Heidelberg , Sasha Levin Subject: [PATCH 6.1 876/982] nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm() Date: Wed, 30 Sep 2026 17:26:52 +0200 Message-ID: <20260930152435.568239593@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152416.775402466@linuxfoundation.org> References: <20260930152416.775402466@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aldo Ariel Panzardo [ Upstream commit bf1460acdf8cf5a07c819f59785d40f20d113099 ] 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. Fixes: a69f32af86e3 ("NFC: Socket linked list") Signed-off-by: Aldo Ariel Panzardo Link: https://patch.msgid.link/20260716232657.203145-1-qwe.aldo@gmail.com Signed-off-by: David Heidelberg Signed-off-by: Sasha Levin --- net/nfc/llcp_core.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c index 7b86faf3f4ce5..9ae9b4fde311e 100644 --- a/net/nfc/llcp_core.c +++ b/net/nfc/llcp_core.c @@ -1249,6 +1249,7 @@ static void nfc_llcp_recv_dm(struct nfc_llcp_local *local, struct nfc_llcp_sock *llcp_sock; struct sock *sk; u8 dsap, ssap, reason; + bool connecting = false; dsap = nfc_llcp_dsap(skb); ssap = nfc_llcp_ssap(skb); @@ -1260,6 +1261,7 @@ static void nfc_llcp_recv_dm(struct nfc_llcp_local *local, case LLCP_DM_NOBOUND: case LLCP_DM_REJ: llcp_sock = nfc_llcp_connecting_sock_get(local, dsap); + connecting = true; break; default: @@ -1274,10 +1276,33 @@ static void nfc_llcp_recv_dm(struct nfc_llcp_local *local, sk = &llcp_sock->sk; + lock_sock(sk); + + /* Check if socket was destroyed whilst waiting for the lock */ + if (!sk_hashed(sk)) { + release_sock(sk); + nfc_llcp_sock_put(llcp_sock); + return; + } + + /* + * For DM(NOBOUND)/DM(REJ) the socket is still linked on the + * connecting_sockets list. Unlink it here, under the socket lock, + * before moving it to LLCP_CLOSED: llcp_sock_release() selects the + * list to unlink from by sk_state, so leaving a connecting socket + * in the CLOSED state would make it unlink from the wrong list and + * corrupt the connecting_sockets list / desync the socket refcount. + * This mirrors nfc_llcp_recv_cc(). + */ + if (connecting) + nfc_llcp_sock_unlink(&local->connecting_sockets, sk); + sk->sk_err = ENXIO; sk->sk_state = LLCP_CLOSED; sk->sk_state_change(sk); + release_sock(sk); + nfc_llcp_sock_put(llcp_sock); } -- 2.53.0