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 A61D14B0CBC for ; Thu, 3 Sep 2026 13:50:31 +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=1788443435; cv=none; b=jiy9aRBU17jzpcX5s62J2eE6gaaPlHxWv3dBWNE7WNLEl5zyguFspUbIIjT2gmGRxYGqjLwZGJ5DPw5PCMKczvdUqsYRPZ+yAJSTEa5wbmrV0s6/OA28+JTU28zYWGH45ofZGMnlt7Ml/BJy4fOHVDMhHoGdv9jegiNw8tMfkg4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788443435; c=relaxed/simple; bh=6Lnzz/VdVg97pVm+GjNPJdYG41JgGaYtehKoKJjNIyU=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=Hv4k1ZiT210k+2pv0n+hDXkRLd6mcS358TaubDqTMCEe7si3+5X5ueoWi/7iMHMVmbUt0u1uQ1JseF+8NxQHsoZO2v8ifw49JQG0iitZnFSUb0mFL/h95Ice8EN8Zm8bbuA2qK508fAVg2Fqsdzz8iU7XwOPosADLajH6MT+xLc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pkGEuOjI; 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="pkGEuOjI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B9711F00A3A; Thu, 3 Sep 2026 13:50:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788443430; bh=IYNHWVp6UmLufSwoXL52Mxkha7fSjfaYlNn3NvGJfOw=; h=Subject:To:Cc:From:Date; b=pkGEuOjIelPPOcBehYrW4qBl1XWNlN8S/rrt3ErJA6NvG70YYdmy4ZP4oKBjrUHE5 xPIdSvULWetdAJDpNZt94QhjyNS6aZ2BSHTkHtsrVQ+amRRzi+d9+2aCSnDizG60FC MvM/mZ857xaacGB204f/G4xy/qwkcmiRlqCEMs4I= Subject: FAILED: patch "[PATCH] NFSD: Prevent client use-after-free during blocked-lock" failed to apply to 5.15-stable tree To: cel@kernel.org,jlayton@kernel.org Cc: From: Date: Thu, 03 Sep 2026 15:32:33 +0200 Message-ID: <2026090333-gutter-request-d440@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x 9026932ac8be4d0ae01db47f23619a98cc57b671 # git commit -s git send-email --to '' --in-reply-to '2026090333-gutter-request-d440@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9026932ac8be4d0ae01db47f23619a98cc57b671 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 9 Jul 2026 13:40:30 -0400 Subject: [PATCH] NFSD: Prevent client use-after-free during blocked-lock reaping A bare lock owner -- its only remaining reference a blocked lock on nn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but no reference keeping the client alive. When the per-net laundromat reaps such a lock, freeing the nbl drops the owner reference held through flc_owner, and the final nfs4_put_stateowner() takes the client's cl_lock. Because the laundromat detaches the nbl first, __destroy_client() no longer finds it, so a concurrent force_expire_client() can free the client before nfs4_put_stateowner() runs, dereferencing cl_lock in freed memory. Pin the client with cl_rpc_users before dropping nn->blocked_locks_lock, and skip clients already expiring, whose blocked locks __destroy_client() frees while holding an owner reference. Take nn->client_lock outside nn->blocked_locks_lock. Every other site holds nn->blocked_locks_lock as a leaf, acquiring no further lock, so placing nn->client_lock outside it cannot form a lock-order cycle. Fixes: 7919d0a27f1e ("nfsd: add a LRU list for blocked locks") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260709-cel-v4-7-1d519d9be0cb@kernel.org Signed-off-by: Chuck Lever diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 142ba7d80539..4acd02f1642c 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -357,6 +357,16 @@ free_blocked_lock(struct nfsd4_blocked_lock *nbl) kref_put(&nbl->nbl_kref, free_nbl); } +/* A blocked lock's flc_owner is its nfs4_lockowner. */ +static struct nfs4_client * +nbl_client(struct nfsd4_blocked_lock *nbl) +{ + struct nfs4_lockowner *lo; + + lo = (struct nfs4_lockowner *)nbl->nbl_lock.c.flc_owner; + return lo->lo_owner.so_client; +} + static void remove_blocked_locks(struct nfs4_lockowner *lo) { @@ -7591,22 +7601,29 @@ nfs4_laundromat(struct nfsd_net *nn) * indefinitely once the lock does become free. */ BUG_ON(!list_empty(&reaplist)); + spin_lock(&nn->client_lock); spin_lock(&nn->blocked_locks_lock); - while (!list_empty(&nn->blocked_locks_lru)) { - nbl = list_first_entry(&nn->blocked_locks_lru, - struct nfsd4_blocked_lock, nbl_lru); + list_for_each_safe(pos, next, &nn->blocked_locks_lru) { + nbl = list_entry(pos, struct nfsd4_blocked_lock, nbl_lru); if (!state_expired(<, nbl->nbl_time)) break; + clp = nbl_client(nbl); + if (is_client_expired(clp)) + continue; + atomic_inc(&clp->cl_rpc_users); list_move(&nbl->nbl_lru, &reaplist); list_del_init(&nbl->nbl_list); } spin_unlock(&nn->blocked_locks_lock); + spin_unlock(&nn->client_lock); while (!list_empty(&reaplist)) { nbl = list_first_entry(&reaplist, struct nfsd4_blocked_lock, nbl_lru); + clp = nbl_client(nbl); list_del_init(&nbl->nbl_lru); free_blocked_lock(nbl); + put_client_no_renew(clp); } #ifdef CONFIG_NFSD_V4_2_INTER_SSC /* service the server-to-server copy delayed unmount list */