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 8B0804A441A for ; Thu, 3 Sep 2026 13:17:16 +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=1788441483; cv=none; b=YS26QXlF4mx4HuGTP/Sw6iVKWM4nr4ABPV6oT2Na+gLVrTW6euxD2GRsOxmXVnpYdoSM+JkdKctJXCzb65obHSxVVOv6H+B0Q1OoqcSTjJeoHPq176mJaRI4W1doPjPBo4okk/ZEWOJXV9CHYGMHe25qxiJBWFtxlBgd6h3w8Jg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788441483; c=relaxed/simple; bh=zqyUrMHn5NTPxPa+YGVj0Yn1/H0nLECOlL/dkD7Wxzw=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=MoiZduEs+Y8m5BN+2wLRYSXsDrwEUjhEqE09alEIQJj7tykVGF6Vu1grCA/nwyXaqUe3IPIJZ/qgWmVPKjDBYCpb41BikKnY2YlWznl640AefhRXzyA2nPyeaCXRSKAh6fBWF5kLPli1TFntGwA8Az+RGabu0yzy86ZdXTBm+Xg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zd+ym65s; 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="zd+ym65s" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D6D881F00AC4; Thu, 3 Sep 2026 13:17:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788441435; bh=y6VMWNt5UtjbwqhdGTaIH3DYlwPxLo8W8Aw+vTm2R8M=; h=Subject:To:Cc:From:Date; b=zd+ym65sjrYmR9lWsE8gOM4z9q3NnGmDbA2a+AT4D65eF2kVnOSvRfpQMJfLwmoGU sVO5bUfuZGbPtK4rqUwjlc6dv+uFYUuFiFZonw1H6bB5s8bHChWeBkXJPFQDLSHXFU LJWiqwU9xdiOjBTMW2JEWyIsPmDcAxSwF9KVD7z8= Subject: FAILED: patch "[PATCH] lockd, nfsd: RCU-protect nlmsvc_ops dispatch" failed to apply to 6.1-stable tree To: jlayton@kernel.org,cel@kernel.org Cc: From: Date: Thu, 03 Sep 2026 15:06:04 +0200 Message-ID: <2026090304-average-cocoa-05b9@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 641e5e20852359b8c31149be4598884e30652f60 # git commit -s git send-email --to '' --in-reply-to '2026090304-average-cocoa-05b9@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 641e5e20852359b8c31149be4598884e30652f60 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Thu, 11 Jun 2026 16:00:59 -0400 Subject: [PATCH] lockd, nfsd: RCU-protect nlmsvc_ops dispatch nlmsvc_ops is published by nfsd_lockd_init() and cleared by nfsd_lockd_shutdown() with plain stores, while lockd dereferences it unguarded from dispatch sites in fs/lockd/svcsubs.c. The pointer targets nfsd's .rodata and the fopen/fclose callbacks live in nfsd's .text, so a stale load after rmmod nfsd results in either a NULL deref or a module-text use-after-free. Declare nlmsvc_ops as __rcu, publish via rcu_assign_pointer(), clear via RCU_INIT_POINTER() + synchronize_rcu(). Add a struct module *owner field to nlmsvc_binding and pin the module across indirect calls with try_module_get/module_put. When the binding is torn down, fall back to fput() to avoid leaking struct file references. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20260611-nfsd-testing-v2-16-5b90e276f2d9@kernel.org Signed-off-by: Chuck Lever diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c index 490551369ef2..ee90e743064a 100644 --- a/fs/lockd/svc.c +++ b/fs/lockd/svc.c @@ -47,7 +47,7 @@ static struct svc_program nlmsvc_program; -const struct nlmsvc_binding *nlmsvc_ops; +const struct nlmsvc_binding __rcu *nlmsvc_ops; EXPORT_SYMBOL_GPL(nlmsvc_ops); static DEFINE_MUTEX(nlmsvc_mutex); @@ -142,7 +142,7 @@ lockd(void *vrqstp) nlmsvc_retry_blocked(rqstp); svc_recv(rqstp, 0); } - if (nlmsvc_ops) + if (rcu_access_pointer(nlmsvc_ops)) nlmsvc_invalidate_all(); nlm_shutdown_hosts(); cancel_delayed_work_sync(&ln->grace_period_end); diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c index 78e675470c4b..080dffce9d8e 100644 --- a/fs/lockd/svc4proc.c +++ b/fs/lockd/svc4proc.c @@ -128,7 +128,7 @@ nlm4svc_lookup_host(struct svc_rqst *rqstp, string caller, bool monitored) { struct nlm_host *host; - if (!nlmsvc_ops) + if (!rcu_access_pointer(nlmsvc_ops)) return NULL; host = nlmsvc_lookup_host(rqstp, caller.data, caller.len); if (!host) @@ -894,7 +894,7 @@ static __be32 nlm4svc_proc_granted_res(struct svc_rqst *rqstp) { struct nlm4_res_wrapper *argp = rqstp->rq_argp; - if (!nlmsvc_ops) + if (!rcu_access_pointer(nlmsvc_ops)) return rpc_success; if (nlm4_netobj_to_cookie(&argp->cookie, &argp->xdrgen.cookie)) diff --git a/fs/lockd/svcproc.c b/fs/lockd/svcproc.c index 386a881b520f..d410b8c69893 100644 --- a/fs/lockd/svcproc.c +++ b/fs/lockd/svcproc.c @@ -133,7 +133,7 @@ nlm3svc_lookup_host(struct svc_rqst *rqstp, string caller, bool monitored) { struct nlm_host *host; - if (!nlmsvc_ops) + if (!rcu_access_pointer(nlmsvc_ops)) return NULL; host = nlmsvc_lookup_host(rqstp, caller.data, caller.len); if (!host) @@ -924,7 +924,7 @@ static __be32 nlmsvc_proc_granted_res(struct svc_rqst *rqstp) { struct nlm_res_wrapper *argp = rqstp->rq_argp; - if (!nlmsvc_ops) + if (!rcu_access_pointer(nlmsvc_ops)) return rpc_success; if (nlm_netobj_to_cookie(&argp->cookie, &argp->xdrgen.cookie)) diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c index d7ada90dc048..e44eb20d3453 100644 --- a/fs/lockd/svcsubs.c +++ b/fs/lockd/svcsubs.c @@ -90,22 +90,35 @@ int lock_to_openmode(struct file_lock *lock) static __be32 nlm_do_fopen(struct svc_rqst *rqstp, struct nlm_file *file, int mode) { + const struct nlmsvc_binding *ops; __be32 nlmerr = nlm__int__failed; __be32 deferred = 0; int error; int m; + rcu_read_lock(); + ops = rcu_dereference(nlmsvc_ops); + if (!ops || !try_module_get(ops->owner)) { + rcu_read_unlock(); + return nlm__int__failed; + } + rcu_read_unlock(); + for (m = O_RDONLY; m <= O_WRONLY; m++) { struct file **fp = &file->f_file[m]; if (mode != O_RDWR && mode != m) continue; - if (*fp) + if (*fp) { + module_put(ops->owner); return nlm_granted; + } - error = nlmsvc_ops->fopen(rqstp, &file->f_handle, fp, m); - if (!error) + error = ops->fopen(rqstp, &file->f_handle, fp, m); + if (!error) { + module_put(ops->owner); return nlm_granted; + } dprintk("lockd: open failed (errno %d)\n", error); switch (error) { @@ -122,6 +135,7 @@ static __be32 nlm_do_fopen(struct svc_rqst *rqstp, } } + module_put(ops->owner); return deferred ? deferred : nlmerr; } @@ -185,6 +199,33 @@ nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result, goto out_unlock; } +/* + * Release the struct file references held by a nlm_file. + */ +static void nlm_release_files(struct nlm_file *file) +{ + const struct nlmsvc_binding *ops; + bool have_ops; + + rcu_read_lock(); + ops = rcu_dereference(nlmsvc_ops); + have_ops = ops && try_module_get(ops->owner); + rcu_read_unlock(); + + if (have_ops) { + if (file->f_file[O_RDONLY]) + ops->fclose(file->f_file[O_RDONLY]); + if (file->f_file[O_WRONLY]) + ops->fclose(file->f_file[O_WRONLY]); + module_put(ops->owner); + } else { + if (file->f_file[O_RDONLY]) + fput(file->f_file[O_RDONLY]); + if (file->f_file[O_WRONLY]) + fput(file->f_file[O_WRONLY]); + } +} + /* * Delete a file after having released all locks, blocks and shares */ @@ -194,10 +235,7 @@ nlm_delete_file(struct nlm_file *file) nlm_debug_print_file("closing file", file); if (!hlist_unhashed(&file->f_list)) { hlist_del(&file->f_list); - if (file->f_file[O_RDONLY]) - nlmsvc_ops->fclose(file->f_file[O_RDONLY]); - if (file->f_file[O_WRONLY]) - nlmsvc_ops->fclose(file->f_file[O_WRONLY]); + nlm_release_files(file); kfree(file); } else { printk(KERN_WARNING "lockd: attempt to release unknown file!\n"); diff --git a/fs/nfsd/lockd.c b/fs/nfsd/lockd.c index 6fe1325815e0..72a5b499839d 100644 --- a/fs/nfsd/lockd.c +++ b/fs/nfsd/lockd.c @@ -92,6 +92,7 @@ nlm_fclose(struct file *filp) } static const struct nlmsvc_binding nfsd_nlm_ops = { + .owner = THIS_MODULE, .fopen = nlm_fopen, /* open file for locking */ .fclose = nlm_fclose, /* close file */ }; @@ -100,11 +101,12 @@ void nfsd_lockd_init(void) { dprintk("nfsd: initializing lockd\n"); - nlmsvc_ops = &nfsd_nlm_ops; + rcu_assign_pointer(nlmsvc_ops, &nfsd_nlm_ops); } void nfsd_lockd_shutdown(void) { - nlmsvc_ops = NULL; + RCU_INIT_POINTER(nlmsvc_ops, NULL); + synchronize_rcu(); } diff --git a/include/linux/lockd/bind.h b/include/linux/lockd/bind.h index b614e0deea72..db8207d4059f 100644 --- a/include/linux/lockd/bind.h +++ b/include/linux/lockd/bind.h @@ -16,17 +16,23 @@ struct svc_rqst; struct rpc_task; struct rpc_clnt; struct super_block; +struct module; -/* - * This is the set of functions for lockd->nfsd communication +/** + * struct nlmsvc_binding - lockd -> nfsd callback table + * @owner: module that provides this binding. + * @fopen: open a file by NFS file handle on behalf of an NLM request. + * @fclose: close a file that was previously opened via @fopen. + * Implementations MUST be semantically equivalent to fput(). */ struct nlmsvc_binding { + struct module *owner; int (*fopen)(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp, int flags); void (*fclose)(struct file *filp); }; -extern const struct nlmsvc_binding *nlmsvc_ops; +extern const struct nlmsvc_binding __rcu *nlmsvc_ops; /* * Similar to nfs_client_initdata, but without the NFS-specific