From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794586004; b=zv/ArpAVdjjK6I7nq4t5KPCB5pQAF3GugWaj4OFVdynner5gJTo6ZWBHSnacNOX4ycpo 02K2hNwXooECMF69NBKY0HWBRjqlVCEPADzdV+RuGnsqdnJoynBbVpYz00da9hvCCQfi4 ac2zSjQc7q0i+bv4jTkHfFLYHzRPnC8IJyOHxjDfcwzH/2Zwvvzuu2BvPlCNjY0ztFNSm ie6864noqkLb/EOPnTRte1hig33F7UMmYU30+lL0K+HX3IEKQwb48UK8UhO6uk/3lWyII PIqSWQVAHXr5Hp5luo1WEb3ZXQVUnBcwIBUsRZwXT1MXAnXcuPsHXPtpLzltR0p3Scg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794586004; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=ke8dwbJwhHcbPT+Y0CFmRqYxqrsmM4p/Dn6ZPz4I6B8=; b=EpW59ZFdGrYbl0sekTt1dhCZ3IgwCWil+jPqRH/1Trr28M33qy2nSkPnxnj4DUbxGiKD C3TA7YTipaMO9tTZP6tt8O1b+8Hv47wydOPqkbE+DS+w4UKl8IiF3PNBPF0fbXWdiAtWe s4iRjnoxINy/ZpMejHQ8A/kwb3wDD7PWPlkre3sRohbsohOluLeze5ZAqM7sty4Io9IHL H9tqThPteC0FYOR2h9Fyy2jXo8mXXEYqNKo6K9yKvKfLaJDyyqJDKXAC5B6+ficSVE8rd DSERPDrhW4kUPpxLGNntQB7Ut4uqz+5vmtxuoWUxyUy7mJyJtkmR8FeCLXsWHjJs/CQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=uCMFJbiM; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C86DA606B5C6; Fri, 13 Nov 2026 16:06:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=uCMFJbiM Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41F111F000C4; Fri, 13 Nov 2026 16:06:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794586004; bh=ke8dwbJwhHcbPT+Y0CFmRqYxqrsmM4p/Dn6ZPz4I6B8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=uCMFJbiMs5EYBrNVIfcsWcs1B7HBBFv8hmlINBqMWAc7pRTLFTSDv5naZ2Uy7+JM8 0ByNRR43xNXsMEhtjQ0SIlLjCE+dNtCro5rnSDaOzqinKEdyVgGybHiewAid9QoWsX /kmnnkHWmLEyg353sUFYxrePGRfxUZk1blZN5YIQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+5c3ed2a0de3270efc921@syzkaller.appspotmail.com, syzbot+c2ec61adfbcb24e5ec20@syzkaller.appspotmail.com, Eduard Zateev , Michail Andreas Michalopoulos , Paulo Alcantara , Sasha Levin Subject: [PATCH 6.18 012/686] smb: client: hold server info until cifsd exits Date: Fri, 13 Nov 2026 10:42:25 -0500 Message-ID: <20261113153821.340071445@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eduard Zateev [ Upstream commit 482c117c6dbeee382790168af10959810450ab09 ] The last session reference can be dropped while the cifsd demultiplex thread is still running clean_demultiplex_info(). That thread frees TCP_Server_Info there, racing with cifs_put_tcp_session() as it releases the server crypto state. syzbot reported a KASAN use-after-free in cifs_crypto_secmech_release(). Keep an object reference for the cifsd thread. Defer final crypto, session-key, network namespace, string, and structure cleanup until both the last session reference and the thread reference are dropped. Drop the thread reference after clean_demultiplex_info() has finished using the server. Build-tested with ARCH=arm64 and W=1 for fs/smb/client/connect.o. The KASAN reproducer was not run on the patched kernel. Fixes: a5c3e1c725af ("Revert "cifs: No need to send SIGKILL to demux_thread during umount"") Reported-by: syzbot+5c3ed2a0de3270efc921@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5c3ed2a0de3270efc921 Reported-by: syzbot+c2ec61adfbcb24e5ec20@syzkaller.appspotmail.com Closes: https://syzbot.org/bug?extid=c2ec61adfbcb24e5ec20 Assisted-by: LLM OpenAI Codex Signed-off-by: Eduard Zateev Cc: stable@vger.kernel.org Tested-by: Michail Andreas Michalopoulos Signed-off-by: Paulo Alcantara Signed-off-by: Sasha Levin --- fs/smb/client/cifsglob.h | 2 ++ fs/smb/client/connect.c | 33 +++++++++++++++++++++------------ 2 files changed, 23 insertions(+), 12 deletions(-) diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h index 8d751026dd4a2..d529446e4984b 100644 --- a/fs/smb/client/cifsglob.h +++ b/fs/smb/client/cifsglob.h @@ -16,6 +16,7 @@ #include #include #include +#include #include #include #include @@ -678,6 +679,7 @@ struct TCP_Server_Info { spinlock_t srv_lock; /* protect anything here that is not protected */ __u64 conn_id; /* connection identifier (useful for debugging) */ int srv_count; /* reference counter */ + refcount_t obj_refs; /* struct lifetime: srv_count users + cifsd */ int rfc1001_sessinit; /* whether to estasblish netbios session */ bool with_rfc1001; /* if netbios session is used */ /* 15 character server name + 0x20 16th byte indicating type = srv */ diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index fa7c2f70b6ed3..0a60c411aba67 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -1059,6 +1059,19 @@ cifs_enable_signing(struct TCP_Server_Info *server, bool mnt_sign_required) return 0; } +static void cifs_tcp_server_put(struct TCP_Server_Info *server) +{ + if (!refcount_dec_and_test(&server->obj_refs)) + return; + + cifs_crypto_secmech_release(server); + kfree_sensitive(server->session_key.response); + put_net(cifs_net_ns(server)); + kfree(server->leaf_fullpath); + kfree(server->hostname); + kfree_sensitive(server); +} + static noinline_for_stack void clean_demultiplex_info(struct TCP_Server_Info *server) { @@ -1144,14 +1157,11 @@ clean_demultiplex_info(struct TCP_Server_Info *server) */ } - put_net(cifs_net_ns(server)); - kfree(server->leaf_fullpath); - kfree(server->hostname); - kfree_sensitive(server); - length = atomic_dec_return(&tcpSesAllocCount); if (length > 0) mempool_resize(cifs_req_poolp, length + cifs_min_rcv); + + cifs_tcp_server_put(server); } static int @@ -1730,7 +1740,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect) else cancel_delayed_work_sync(&server->reconnect); - /* For secondary channels, we pick up ref-count on the primary server */ + /* For secondary channels, drop the reference on the primary server */ if (SERVER_IS_CHAN(server)) cifs_put_tcp_session(server->primary_server, from_reconnect); @@ -1738,15 +1748,11 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect) server->tcpStatus = CifsExiting; spin_unlock(&server->srv_lock); - cifs_crypto_secmech_release(server); - - kfree_sensitive(server->session_key.response); - server->session_key.response = NULL; - server->session_key.len = 0; - task = xchg(&server->tsk, NULL); if (task) send_sig(SIGKILL, task, 1); + + cifs_tcp_server_put(server); } struct TCP_Server_Info * @@ -1768,6 +1774,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx, rc = -ENOMEM; goto out_err; } + refcount_set(&tcp_ses->obj_refs, 1); tcp_ses->hostname = kstrdup(ctx->server_hostname, GFP_KERNEL); if (!tcp_ses->hostname) { @@ -1906,6 +1913,8 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx, module_put(THIS_MODULE); goto out_err_crypto_release; } + /* Keep the server alive until the demultiplex thread has exited */ + refcount_inc(&tcp_ses->obj_refs); /* thread created, put it on the list */ spin_lock(&cifs_tcp_ses_lock); list_add(&tcp_ses->tcp_ses_list, &cifs_tcp_ses_list); -- 2.53.0