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[2003:dc:6f4c:be00:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4983600bd6esm12209506f8f.28.2026.11.11.08.18.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 08:18:39 -0800 (PST) From: Max Kellermann To: xiubli@redhat.com, idryomov@gmail.com, amarkuze@redhat.com, ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Max Kellermann , stable@vger.kernel.org Subject: [PATCH 5/9] ceph: fix mdsmap use-after-free in mds_peer_reset() Date: Wed, 11 Nov 2026 17:18:26 +0100 Message-ID: <20261111161830.1336485-6-max.kellermann@ionos.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261111161830.1336485-1-max.kellermann@ionos.com> References: <20261111161830.1336485-1-max.kellermann@ionos.com> X-Mailing-List: ceph-devel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit mds_peer_reset() reads the MDS state from mdsc->mdsmap without holding mdsc->mutex, but ceph_mdsc_handle_mdsmap() replaces the mdsmap and frees the old one under that mutex. A peer reset often coincides with an MDS failover, which is exactly when a new mdsmap arrives, so this can read freed memory. Read the state while holding mdsc->mutex. The messenger drops con->mutex before calling ->peer_reset(), so no lock is held here. Fixes: cbcb358b744b ("ceph: skip reconnecting if MDS is not ready") Cc: stable@vger.kernel.org Signed-off-by: Max Kellermann --- fs/ceph/mds_client.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index a43ce23d48f4..aa4406fd65b9 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -7300,13 +7300,19 @@ static void mds_peer_reset(struct ceph_connection *con) { struct ceph_mds_session *s = con->private; struct ceph_mds_client *mdsc = s->s_mdsc; + int mds_state; int rc; pr_warn_client(mdsc->fsc->client, "mds%d closed our session\n", s->s_mds); + /* ceph_mdsc_handle_mdsmap() replaces and frees the mdsmap */ + mutex_lock(&mdsc->mutex); + mds_state = ceph_mdsmap_get_state(mdsc->mdsmap, s->s_mds); + mutex_unlock(&mdsc->mutex); + if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO || - ceph_mdsmap_get_state(mdsc->mdsmap, s->s_mds) < CEPH_MDS_STATE_RECONNECT) + mds_state < CEPH_MDS_STATE_RECONNECT) return; /* -- 2.53.0