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Thu, 27 Aug 2026 21:19:29 -0700 (PDT) Received: from mac.lan ([136.55.173.105]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-66e4ed2a78bsm290978d50.20.2026.08.27.21.19.29 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 27 Aug 2026 21:19:29 -0700 (PDT) From: "Cen Zhang (Microsoft Security FORGE Labs)" To: cel@kernel.org, jlayton@kernel.org Cc: neil@brown.name, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, bfields@fieldses.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, xmei5@asu.edu, tgopinath@linux.microsoft.com, kys@microsoft.com, blbllhy@gmail.com Subject: [PATCH] nfsd: hold cl_lock in client_has_state() Date: Fri, 28 Aug 2026 00:19:25 -0400 Message-ID: <20260828041925.36758-1-blbllhy@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit client_has_openowners() walks clp->cl_openowners and reads so_stateids without clp->cl_lock. nfs4_put_stateowner() unhashes that openowner under cl_lock and then frees it, so a concurrent EXCHANGE_ID with mismatched creds can use-after-free the nfs4_openowner. BUG: KASAN: slab-use-after-free in client_has_state+0x10a/0x140 fs/nfsd/nfs4state.c:3718 client_has_openowners() nfsd4_exchange_id nfsd4_proc_compound nfsd_dispatch svc_process Take clp->cl_lock while client_has_state() walks the openowner list. Fixes: 4eaea1342507 ("nfsd: improve client_has_state to check for unused openowners") Reported-by: Xiang Mei (Microsoft) Cc: AutonomousCodeSecurity@microsoft.com Cc: stable@vger.kernel.org Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) --- fs/nfsd/nfs4state.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 18e17232cf94..8d7a4c2eadbe 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -4216,12 +4216,18 @@ nfsd4_set_ex_flags(struct nfs4_client *new, struct nfsd4_exchange_id *clid) static bool client_has_openowners(struct nfs4_client *clp) { struct nfs4_openowner *oo; + bool found = false; + spin_lock(&clp->cl_lock); list_for_each_entry(oo, &clp->cl_openowners, oo_perclient) { - if (!list_empty(&oo->oo_owner.so_stateids)) - return true; + if (!list_empty(&oo->oo_owner.so_stateids)) { + found = true; + break; + } } - return false; + spin_unlock(&clp->cl_lock); + + return found; } static bool client_has_state(struct nfs4_client *clp) base-commit: 1b78070aaef63512688aebfbc82365ef9d6660f1 -- 2.55.0