From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 6B9ED14BF92; Mon, 6 Apr 2026 13:47:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775483229; cv=none; b=mOxEGU5O1B54MmWrGI8fLXwohQGAs7p2FeD45yydhKk8A4pefflqvyu8NvJg2DAkzgehpn2419ZAOz3bTV5Ao4WlRWFuWHLL+feYvbLCfo/xONm4iKHae4D4+s6KQyhBXmYVKnkXl4pwNE2+ASUKl7SMpUeGcJ+IujPZdQ/uWgg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775483229; c=relaxed/simple; bh=4ZQRFVzdUCijd8idg1rAWi6+HbzaURjFDDhmzLTKBPU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KXWKjz2ByVf4OCk0sKMPFK96xtRYLfsKpGt+POLtnshXpXs+E64biiz/SfxV9EAwwWpOMb/NrB0lvvUbgDt1IPZ7hG+u6RM+jwAAw6N/9w19l6dioPptXHGUFJoL+IQ9cdRLFjFHAU2c8xTDA0kq07jaOunF0YBNFQ6NLxcZkko= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1eJ/mcVd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1eJ/mcVd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86E06C2BC9E; Mon, 6 Apr 2026 13:47:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775483229; bh=4ZQRFVzdUCijd8idg1rAWi6+HbzaURjFDDhmzLTKBPU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1eJ/mcVd3fMZ6m3/BWlT1UZwgIiCtE2SPxk9SaIE1naduA0M3HGVf0yJnWxVW4vr6 yorsihbLnZ8BPbK66ozekiC6J9gZzfwrFYcypmgpm5JcKo/9fjnrsbrODv8Spsszpt 8ziLXJLKo7bWfuwDEzitK92lufx+A8xvOX87e/e4= From: Greg Kroah-Hartman To: linux-cifs@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Namjae Jeon , Steve French , Sergey Senozhatsky , Tom Talpey , stable Subject: [PATCH 3/3] ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc Date: Mon, 6 Apr 2026 15:46:48 +0200 Message-ID: <2026040647-reset-uninstall-1145@gregkh> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026040644-brussels-dab-6f99@gregkh> References: <2026040644-brussels-dab-6f99@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2611; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=4ZQRFVzdUCijd8idg1rAWi6+HbzaURjFDDhmzLTKBPU=; b=owGbwMvMwCRo6H6F97bub03G02pJDJmXd7r/q+V5ZHeAwbvDvqp/SfnK1mPVKXOYVNkEjO9sM GLf1LCyI5aFQZCJQVZMkeXLNp6j+ysOKXoZ2p6GmcPKBDKEgYtTACby/inDggW+lQWPis6FrDjd 9qXZy/aMh1uLN8P8qJq4zVP3X2FRvaw0p+9s3ovlekfcAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit The kernel ASN.1 BER decoder calls action callbacks incrementally as it walks the input. When ksmbd_decode_negTokenInit() reaches the mechToken [2] OCTET STRING element, ksmbd_neg_token_alloc() allocates conn->mechToken immediately via kmemdup_nul(). If a later element in the same blob is malformed, then the decoder will return nonzero after the allocation is already live. This could happen if mechListMIC [3] overrunse the enclosing SEQUENCE. decode_negotiation_token() then sets conn->use_spnego = false because both the negTokenInit and negTokenTarg grammars failed. The cleanup at the bottom of smb2_sess_setup() is gated on use_spnego: if (conn->use_spnego && conn->mechToken) { kfree(conn->mechToken); conn->mechToken = NULL; } so the kfree is skipped, causing the mechToken to never be freed. This codepath is reachable pre-authentication, so untrusted clients can cause slow memory leaks on a server without even being properly authenticated. Fix this up by not checking check for use_spnego, as it's not required, so the memory will always be properly freed. At the same time, always free the memory in ksmbd_conn_free() incase some other failure path forgot to free it. Cc: Namjae Jeon Cc: Steve French Cc: Sergey Senozhatsky Cc: Tom Talpey Cc: linux-cifs@vger.kernel.org Cc: stable Assisted-by: gregkh_clanker_t1000 Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/connection.c | 1 + fs/smb/server/smb2pdu.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/smb/server/connection.c b/fs/smb/server/connection.c index 1bb2081c492c..26cfce344861 100644 --- a/fs/smb/server/connection.c +++ b/fs/smb/server/connection.c @@ -96,6 +96,7 @@ void ksmbd_conn_free(struct ksmbd_conn *conn) xa_destroy(&conn->sessions); kvfree(conn->request_buf); kfree(conn->preauth_info); + kfree(conn->mechToken); if (atomic_dec_and_test(&conn->refcnt)) { conn->transport->ops->free_transport(conn->transport); kfree(conn); diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 6f658dc20758..a344937595f4 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -1915,7 +1915,7 @@ int smb2_sess_setup(struct ksmbd_work *work) else if (rc) rsp->hdr.Status = STATUS_LOGON_FAILURE; - if (conn->use_spnego && conn->mechToken) { + if (conn->mechToken) { kfree(conn->mechToken); conn->mechToken = NULL; } -- 2.53.0