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 47B721B4F1F for ; Sun, 21 Jun 2026 16:25:59 +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=1782059160; cv=none; b=VslD3hVdNv7xFTLC9TltiUeydwgUS2iwqU2dlKFSyKKOquTlDZNSFaOy36c4aKsRr8jPqvphhb5DjTaMLjcWJhMWdZOVLKkDBghy831dBUAx6SL2xN2RfwdbNrXhpD9tF5opS208uqLh8r1cFAwX7Fps3r0tkNdNyK22+iPQaS8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782059160; c=relaxed/simple; bh=cx7d39y+i+MhyXD0t92sziWAwhdXa8UIbH5Zg8sw8zA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ViUgHAjDeYRJStx4fCGMYDiXLvw0hJxY7wfrSXGED2aIn5k/lvJnzTv9fKfW414YUqEsIJAQQ3+cOXjSKmlVtnFWUnAGJncI5VQa2gDWB+gJBFgKsDV1zkRaLnPm3Eq38EsUsiLeUUBqa9+wUZ1LT0a+AjQ4TIteXPzBhZ8pBi8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PKBQ52DF; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PKBQ52DF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 55CCF1F000E9; Sun, 21 Jun 2026 16:25:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782059158; bh=14RcKjKWjB9sN1q9ZY+S8mQ8DhuyHK5JPFkyrJkzLTw=; h=From:To:Cc:Subject:Date; b=PKBQ52DFnsLPf1KHeu3lF+oXABScm5nCPI7pbz67dQ91mkgO8YP8BfW3v7bdgQS9d YttHfY+13ByXO6dOseio2z2Ullh4SZHUuVK+NWoKMFG1lHlx1F2AIavQIVJpRJp6eX n82EaaWicfm5HGtJcZQJQejicnpTH/dpIK02rMnBoCWwU/IA/DXN6SuAddon3JoSEI QZhS/x90IOo9xdn2jqgJZUfgnqjIP8DLUB4584bTPPKRgBWdGNYvIpye6ry8Avk408 Zgj//Md1coliFCqPA39QukQ9mPUHE/MiN5PmjWoCcx2s7zVoy1B3hJuSczFNZ8L/Wl QOE9BXZcloOyg== From: Chuck Lever To: NeilBrown , Jeff Layton , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: , XIAO WU Subject: [PATCH] NFSD: Guard admin state-revocation walks with NFSD_NET_UP Date: Sun, 21 Jun 2026 12:25:51 -0400 Message-ID: <20260621162551.2469460-1-cel@kernel.org> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Writing to /proc/fs/nfsd/unlock_filesystem, or sending the NFSD_CMD_UNLOCK_FILESYSTEM or NFSD_CMD_UNLOCK_EXPORT netlink command, walks the NFSv4 client hash tables to revoke open state and cancel async COPY operations. All three handlers gate that walk on nn->nfsd_serv, but a listener added via portlist or netlink listener_set sets nn->nfsd_serv before any nfsd thread starts. nfsd_startup_net() has not yet allocated nn->conf_id_hashtbl, so the walkers dereference a NULL table. A local administrator with CAP_SYS_ADMIN can crash the kernel this way without ever starting the server. nn->nfsd_serv is set when the service is created, which precedes table allocation. NFSD_NET_UP instead brackets the window where the tables are live: set at the end of nfsd_startup_net() and cleared in nfsd_shutdown_net() after they are freed, both under nfsd_mutex. Gating the three unlock paths on NFSD_NET_UP fixes the startup-time NULL dereference while preserving the earlier post-shutdown use-after-free fix. Reported-by: XIAO WU Fixes: 1ac3629bf012 ("nfsd: prepare for supporting admin-revocation of state") Signed-off-by: Chuck Lever --- fs/nfsd/nfs4proc.c | 7 +++---- fs/nfsd/nfs4state.c | 14 ++++++-------- fs/nfsd/nfsctl.c | 6 +++--- 3 files changed, 12 insertions(+), 15 deletions(-) diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index c413ed0810b9..8351ccaae59c 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1588,10 +1588,9 @@ static bool nfsd4_copy_on_sb(const struct nfsd4_copy *copy, * @net: net namespace containing the copy operations * @sb: targeted superblock * - * Context: Caller must hold nfsd_mutex with nn->nfsd_serv confirmed - * non-NULL. nfs4_state_destroy_net() frees conf_id_hashtbl - * at server shutdown without clearing the pointer, so a - * walk without these guarantees iterates freed slab memory. + * Context: Caller must hold nfsd_mutex with NFSD_NET_UP set. Outside + * that window nn->conf_id_hashtbl is unallocated or freed, + * so the walk would dereference a NULL or dangling pointer. */ void nfsd4_cancel_copy_by_sb(struct net *net, struct super_block *sb) { diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 4ae5d65c056a..a4398dc861a5 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1946,10 +1946,9 @@ static void revoke_one_stid(struct nfsd_net *nn, struct nfs4_client *clp, * The clients which own the states will subsequently be notified that the * states have been "admin-revoked". * - * Context: Caller must hold nfsd_mutex with nn->nfsd_serv confirmed - * non-NULL. nfs4_state_destroy_net() frees conf_id_hashtbl - * at server shutdown without clearing the pointer, so a - * walk without these guarantees iterates freed slab memory. + * Context: Caller must hold nfsd_mutex with NFSD_NET_UP set. Outside + * that window nn->conf_id_hashtbl is unallocated or freed, + * so the walk would dereference a NULL or dangling pointer. */ void nfsd4_revoke_states(struct nfsd_net *nn, struct super_block *sb) { @@ -2024,10 +2023,9 @@ static struct nfs4_stid *find_one_export_stid(struct nfs4_client *clp, * Userspace (exportfs -u) sends this after removing the last client * for a path, enabling the underlying filesystem to be unmounted. * - * Context: Caller must hold nfsd_mutex with nn->nfsd_serv confirmed - * non-NULL. nfs4_state_destroy_net() frees conf_id_hashtbl - * at server shutdown without clearing the pointer, so a - * walk without these guarantees iterates freed slab memory. + * Context: Caller must hold nfsd_mutex with NFSD_NET_UP set. Outside + * that window nn->conf_id_hashtbl is unallocated or freed, + * so the walk would dereference a NULL or dangling pointer. */ void nfsd4_revoke_export_states(struct nfsd_net *nn, const struct path *path) { diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index caf59421f8f4..bc16fc7ca24f 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -299,7 +299,7 @@ static ssize_t write_unlock_fs(struct file *file, char *buf, size_t size) error = nlmsvc_unlock_all_by_sb(path.dentry->d_sb); mutex_lock(&nfsd_mutex); nn = net_generic(netns(file), nfsd_net_id); - if (nn->nfsd_serv) { + if (test_bit(NFSD_NET_UP, &nn->flags)) { nfsd4_cancel_copy_by_sb(netns(file), path.dentry->d_sb); nfsd4_revoke_states(nn, path.dentry->d_sb); } else { @@ -2424,7 +2424,7 @@ int nfsd_nl_unlock_filesystem_doit(struct sk_buff *skb, error = nlmsvc_unlock_all_by_sb(path.dentry->d_sb); mutex_lock(&nfsd_mutex); - if (nn->nfsd_serv) { + if (test_bit(NFSD_NET_UP, &nn->flags)) { nfsd4_cancel_copy_by_sb(net, path.dentry->d_sb); nfsd4_revoke_states(nn, path.dentry->d_sb); } else { @@ -2471,7 +2471,7 @@ int nfsd_nl_unlock_export_doit(struct sk_buff *skb, struct genl_info *info) return error; mutex_lock(&nfsd_mutex); - if (nn->nfsd_serv) { + if (test_bit(NFSD_NET_UP, &nn->flags)) { nfsd_file_close_export(net, &path); nfsd4_revoke_export_states(nn, &path); } else -- 2.54.0