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 2A94D4195A0 for ; Thu, 9 Jul 2026 17:40:44 +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=1783618845; cv=none; b=Pz/qpDtmZuafLSuAxg+tqzDTKa+6N0AEeZLvwiXkJnL7XKvPtfSPxxgXKL3JMko3wIy12NFXoP3mYH2BX21AHh8u7WTiGJXz9Z3hnTgkqqcHFX0BIdK9DRqnuIbKBc13ZD2dLUpL9ewdLJ3i0w+CZGAyQMM8QLuZliCcQ94smUk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783618845; c=relaxed/simple; bh=7eLmnMwK8q+eAHwq7CBhow5JoNUl5reblYb9N9juiZw=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=A8KbDJKmIjbj6Syn/3ffZdQB4JEfPj10bRFVpfdjeLNDVInMkt2vIXWYmE+I4PCl0eDEClPEhGNPWd0UpNBtP9Cj4VteQGaLfF5VQVffRP2us2nnuYfX2dM7ybphwO9ASooUEDNz4OA28lhVUXBelfF8MGDbEhKxxSaktobSCdE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TvLFBM95; 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="TvLFBM95" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84A7B1F00A3E; Thu, 9 Jul 2026 17:40:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783618844; bh=DtMo+OTDVTaohTD7fLBtUExcgy3ncWSmLJKUAhryAug=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=TvLFBM95NCDwwFg9GiYwFldgwRB8//X3J21XUdVFif6RQoCDXKB//p1MrXDZ7u3iJ k0ECU3JlgigWNMaj/L7VS8oZFyIMlvAqPCSwpLOrEKS2Ypcdl2xLCDBl6geSLD1HFn FFwobqBnKxSJVBnvly9EJURXxw7LjHaDhuqScs9enuRwhF1nMCYmX5Iw5Q9/H7Xz/V BCSynzdJBdEOA3AY98iZukIY10UFJEQFiVDdTXzJtieNyVg7n6cILdI1QEClrMRZ84 letoqv9KEjpBMbTt103NRxi0WPfgFApGHbuzYneIfzAERJGU57wtepjnR+YeqHTsdT hpSpzs3McbkWw== From: Chuck Lever Date: Thu, 09 Jul 2026 13:40:30 -0400 Subject: [PATCH v4 7/9] NFSD: Prevent client use-after-free during blocked-lock reaping Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260709-cel-v4-7-1d519d9be0cb@kernel.org> References: <20260709-cel-v4-0-1d519d9be0cb@kernel.org> In-Reply-To: <20260709-cel-v4-0-1d519d9be0cb@kernel.org> To: Jeff Layton , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Chuck Lever X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2984; i=cel@kernel.org; h=from:subject:message-id; bh=7eLmnMwK8q+eAHwq7CBhow5JoNUl5reblYb9N9juiZw=; b=owEBbQKS/ZANAwAKATNqszNvZn+XAcsmYgBqT90VbHhhkC4uBwunTyxlmq/kE0UmeAP3ufY9E zYQ5rAi91+JAjMEAAEKAB0WIQQosuWwEobfJDzyPv4zarMzb2Z/lwUCak/dFQAKCRAzarMzb2Z/ lyaYD/0W6LpRmE8DmKmAGeSFFqD/+PxbbgxSoqHPETwllAWC5w1ZVgc4yi9vzbJQEQmLK48/LrK c17kjlauKnpHnTcLIpiVBH06SumAes+/1JcjTki2S7WnLXdJN2BiS72Z7XMgMsvWBx5wD209xHf odfpokBZevzw2+mUhlwoN4k7iEnwZ8YX40YYRUSJgJ4humcghu3J8ljz1DvoiFGne5sKgQOVGpR 0dIZCGnPO5Q/W4gP9oUNNQYCrppMx+peUKVD7qOuUm9YgIoWM9cRY5eBk275PC1ivK/TKmzoICQ qCTqGsl67X3zNA6nK4xeIIqAoUlS1Yx/QIQERreugDmM7LZsvW9XL3Y24IrTSHZxey3ndziCEV6 pziXht8ZY6tD3T+jfsTxq+pge9+xDgr5QDSkhLKxks7miqE9pfJJ/DTDvfb27HJWMQdnn8Gu5nY r+mZ4O0A6G4sir8MUjNxOlirpmChbadgwSvKVxQv2BRiGxOx+p+LnApTRFtPknwoA+In5Dbfejf KfQ/rR9dLVt/yIw6KDzKzb2zmH6Rf6+qxh16EkTzCmfg++xCq7GZFmiwo6YXY65TtT+jHJ4pCGT /PKkUvZe1Yultc8mSK4DiPAvbFKJfia2k+CCKxKsaLbXpYxQL+Kn1a+GtuPR9GPGKQftIlK9sq3 qwD2OLR7RWH937Q== X-Developer-Key: i=cel@kernel.org; a=openpgp; fpr=28B2E5B01286DF243CF23EFE336AB3336F667F97 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") Signed-off-by: Chuck Lever --- fs/nfsd/nfs4state.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) 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 */ -- 2.54.0