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 A89F14195A4 for ; Thu, 9 Jul 2026 17:40:40 +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=1783618841; cv=none; b=KRVsdLUrhxoFAPVKCPc7IDXx0dW2s8GYWyu3xa4A7AbqtXGh75cIHbfIVJUD1kWgVIUAmTofufRVFEZdmc8NWEQpd5AH+ZDE/RcwNTqRDn1NZ2b1NvigtAOYStgtz34rqJ8WrFceF7G2BwM4aYBa2EAmcZ9QeoyxyfnaNE8OM1o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783618841; c=relaxed/simple; bh=BGYhbIZdEt1XuBbURBJjf5k9ZTycYt/4iUjdIRqIIkQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=JUcrkT2KcoFYRWODWTZ2W5ybj5oYQ+WNfAiEbR2kMAZAwkiGKPTErrMSZ7psmoYQRFw4B43MZwUZTtTW1rMinzKPwuhvz+iOyUilpN4A9H5lo14ImpwK10bviSLzwRRZRZ9sORMpFB/vaFKRwHVXAh3bunR2NpopLwwFiNIk76c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LIkI0JAx; 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="LIkI0JAx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E24891F000E9; Thu, 9 Jul 2026 17:40:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783618840; bh=7FJ5DYKe4vXr22Y21rio49hpHl4GHogFOlLHfX29HTY=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=LIkI0JAxcwnmcRgcA6lltjSyF+cMsY5AkZjvhzi0GDdNrVwq+bkMtRwDrsFA163gW Zb33YAc4AOdHkq4+3RkQq97Omed9vzCk6z1Qr8XzRlcaGT1csvZZWKI8ZRDs14iSHo sQS1Ty1EqRCuysTmWOWFhLpv53Sdq/MmhA3DqL2m5g+lYxWB+HJdDQDe4Ff/jl3+Pw bqY3xm5nXjQCygEHAZmN3UvhK3L1w++KBcqUhayedsikbNIlkhZIITiHw99647z9kt VF/UpPSS8W52TEuwQ33msJjuTbx0PI2cgTVDbRjqH6bXvO+P5+rhs7M7BJ2u0knT6+ Ai91iZ18ZgH/g== From: Chuck Lever Date: Thu, 09 Jul 2026 13:40:25 -0400 Subject: [PATCH v4 2/9] NFSD: Prevent client use-after-free during delegation revoke 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-v4-2-1d519d9be0cb@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=3853; i=cel@kernel.org; h=from:subject:message-id; bh=BGYhbIZdEt1XuBbURBJjf5k9ZTycYt/4iUjdIRqIIkQ=; b=owEBbQKS/ZANAwAKATNqszNvZn+XAcsmYgBqT90VNL1PffSyS8qm57QyyOJ6MLRHLaFxHv4KN BCfsBKBnjyJAjMEAAEKAB0WIQQosuWwEobfJDzyPv4zarMzb2Z/lwUCak/dFQAKCRAzarMzb2Z/ lxkxEACzGzt3U3+feimCsve46jbeAqRf6g8oLQCO0obO2uwbHcQOD4mpcfYSzRmdmPxkUE76T9r l6lsLUJ1WS1pvJT58++tkvotSrKh9f3xxMesV/KcSIwIm1hBf0bmSUSwbZ+Ijv2wOpfIv5cqCaU pFAn18XFLbq25tZ/BYqEOhYkbIQ1jEz1jX5JUobIbRMncwGrAWRhlFt5sL04groTgeYCyYYP3w1 NFO0Q1jZHF16c7XjO4jD7oC1wsFq1fpnGJdafb0c760lU2ERATD0VWY6XugxIgbJ6lRRjuxKBJV 3ueIuaay53gnrz1GqsHnlO8Z8BDgR7hllmrfIVvBs+7/Le4HThJZ0Ksg5mgJnT8zrTv1jNk+TPf /OI1WDB1+HRK3AozJ6zv8fOo8qtz1Qp2XhlMhcv1Et1uq7wYJ5eGReE0pyGF1E4cdo0y7nbV8qI Hbv19BaDzpzQwfDbkfweqXfqJ+aHiCqj+e9CULa9lQmMS+dUhjlOiM4O6mGAhOEMUglZ2P15Gbe w2fAyzNuFeaf2r/DYeOLySCKdC83uawsvRIX6ijgpw3pw9uA/AkEaZu5nMDFEYGcu9FWUJJwlb7 44Y/VZtvBY2qoyhfJVuMD/kiSk4ocjqrgTNAZKs0YW9sNCl1dKsFtJc/7QQ5CNxomk+X15kD7bp QDLDapA5gVUQZDA== X-Developer-Key: i=cel@kernel.org; a=openpgp; fpr=28B2E5B01286DF243CF23EFE336AB3336F667F97 A delegation stateid holds only a bare pointer to its owning nfs4_client and does not keep it alive. The client survives its stateids only because __destroy_client() drains cl_delegations and cl_revoked before free_client() runs. nfs4_laundromat() breaks that invariant: it unhashes an expired delegation from cl_delegations, drops deleg_lock, then revoke_delegation() relinks it onto cl_revoked under cl_lock. In that window the delegation is on neither list, so client_has_state() can report no remaining state. Every teardown path first requires cl_rpc_users to be zero, but the laundromat holds no such reference. A client whose recalled delegation has just timed out can therefore reach free_client() while revoke_delegation() is still about to dereference cl_lock, a use-after-free. Pin the client with cl_rpc_users across the revoke so teardown blocks until it completes, then reap the delegation from cl_revoked. A client already expiring reaps its own, so skip it and leave the delegation on del_recall_lru. Fixes: 3bd64a5ba171 ("nfsd4: implement SEQ4_STATUS_RECALLABLE_STATE_REVOKED") Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever --- fs/nfsd/netns.h | 6 ++++-- fs/nfsd/nfs4state.c | 23 +++++++++++++++++++++++ 2 files changed, 27 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h index 03724bef10a7..a7bd7b67fa4f 100644 --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -115,7 +115,8 @@ struct nfsd_net { struct list_head client_lru; struct list_head close_lru; - /* protects del_recall_lru and delegation hash/unhash */ + /* protects del_recall_lru and delegation hash/unhash; + * nests outside client_lock */ spinlock_t deleg_lock ____cacheline_aligned; struct list_head del_recall_lru; @@ -124,7 +125,8 @@ struct nfsd_net { struct delayed_work laundromat_work; - /* client_lock protects the client lru list and session hash table */ + /* client_lock protects the client lru list and session hash + * table; nests inside deleg_lock */ spinlock_t client_lock; /* protects blocked_locks_lru */ diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index e000ed3e96e9..efeb2a2e9c8f 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7457,6 +7457,7 @@ nfs4_laundromat(struct nfsd_net *nn) .new_timeo = nn->nfsd4_lease }; struct nfs4_cpntf_state *cps; + struct nfs4_client *clp; copy_stateid_t *cps_t; int i; @@ -7485,6 +7486,18 @@ nfs4_laundromat(struct nfsd_net *nn) dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru); if (!state_expired(<, dp->dl_time)) break; + clp = dp->dl_stid.sc_client; + spin_lock(&nn->client_lock); + if (is_client_expired(clp)) { + spin_unlock(&nn->client_lock); + continue; + } + /* + * Pin without reviving: get_client_locked() would + * flip a courtesy client back to NFSD4_ACTIVE. + */ + atomic_inc(&clp->cl_rpc_users); + spin_unlock(&nn->client_lock); refcount_inc(&dp->dl_stid.sc_count); unhash_delegation_locked(dp, SC_STATUS_REVOKED); list_add(&dp->dl_recall_lru, &reaplist); @@ -7493,8 +7506,18 @@ nfs4_laundromat(struct nfsd_net *nn) while (!list_empty(&reaplist)) { dp = list_first_entry(&reaplist, struct nfs4_delegation, dl_recall_lru); + clp = dp->dl_stid.sc_client; list_del_init(&dp->dl_recall_lru); revoke_delegation(dp); + /* + * Unpin without renewing: put_client_renew() would + * renew the reaped client's lease. + */ + if (atomic_dec_and_lock(&clp->cl_rpc_users, &nn->client_lock)) { + if (is_client_expired(clp)) + wake_up_all(&expiry_wq); + spin_unlock(&nn->client_lock); + } } spin_lock(&nn->client_lock); -- 2.54.0