CVE-2026-98069 (GCVE-0-2026-98069)
Vulnerability from cvelistv5
Published
2026-09-25 10:24
Modified
2026-10-19 09:13
Severity ?
8.1 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net/rds: acquire the fastpath locks in rds_conn_shutdown() rds_conn_shutdown() quiesces the transmit and receive-refill paths by waiting for RDS_IN_XMIT and RDS_RECV_REFILL to be sampled clear, and then runs the transport shutdown and rds_conn_path_reset(). Sampling the bits clear is not the same as owning them: the moment after the wait_event() returns, rds_send_xmit() can re-acquire RDS_IN_XMIT (or rds_ib_recv_refill() can re-acquire RDS_RECV_REFILL) and run concurrently with the teardown. The sender does recheck the connection state after taking the lock, but that recheck is a classic store-buffering pattern: teardown writes the state and reads the bit while the sender writes the bit and reads the state. acquire_in_xmit() is only an acquire operation, so on weakly ordered architectures both sides can miss each other's write, and the transmit path then runs while the transport zeroes its rings (e.g. rds_ib_ring_init()) and rds_send_path_reset() rewrites the transmit state under it. Oracle UEK fixed the same class of crashes - a 14-year tail of BUG_ON()s in rds_ib_sub_signaled(), unexpected op-codes and NULL dereferences in rds_ib_send_cqe_handler() during failover testing - by making the teardown path *acquire* the fastpath bit locks instead of testing them ("rds: Make sure transmit path and connection tear-down does not run concurrently"). Ownership of a single word is decided by RMW atomicity, so no cross-variable ordering is needed. Do the same here: take both locks before calling the transport shutdown, hold them across rds_conn_path_reset(), and release them explicitly with a wake-up afterwards. Both are released with clear_bit_unlock(), so that the ring re-initialization done by the transport shutdown and the transmit state rewritten by rds_send_path_reset() are ordered before either bit is seen clear by the next acquire_in_xmit() or acquire_refill(). The fastpath users of these bits - rds_send_xmit() and rds_ib_recv_refill() - are trylock style and back off while teardown owns the locks, so no new lock dependency is introduced for them. rds_tcp_reset_callbacks() is different: since the previous patch it acquires RDS_IN_XMIT as well, and it blocks doing so, so its wait now spans the teardown instead of at most one send batch. That waiter runs from rds_tcp_accept_one() on the single-threaded krdsd workqueue and holds rds_tcp_accept_lock and t_conn_path_lock while it waits, so a duelling SYN accepted while its path is being torn down parks accept processing for the duration of the teardown - for TCP bounded by the (up to 5 s) drain loop in rds_tcp_conn_path_shutdown(). An IB path's drain in rds_ib_conn_path_shutdown() has no round cap, but no blocking waiter either: rds_tcp_reset_callbacks() is the only blocking acquirer of these bits and waits only on its own TCP path, and the fastpaths are trylock-and-back-off on both transports, so a long IB drain lengthens only that path's own quiesce. The window is narrow: the accept-side state check has to pass before the teardown moves the path to RDS_CONN_DISCONNECTING. Because krdsd is a single global workqueue, everything else queued there - accept processing for other connections and network namespaces, and the flush_workqueue(rds_wq) in rds_tcp_listen_stop() during namespace teardown - waits behind the parked accept worker for that time. It cannot deadlock, although the waits do point at each other: the teardown blocks until the bit's holder releases it, and the holder may be that krdsd accept worker. The holder finishes without needing anything the teardown owns: the sync cancels rds_tcp_reset_callbacks() issues target cp_send_w and cp_recv_w on the path's ordered cp_wq, whose only execution slot is occupied by the blocked cp_down_w itself, so they are pending at most and cancel without flushing - a reliance on cp_wq being ordered that is now noted next to those cancels (on ---truncated---
References
Impacted products
Vendor Product Version
Linux Linux Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
Version: 0f4b1c7e89e699f588807a914ec6e6396c851a72
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/rds: acquire the fastpath locks in rds_conn_shutdown()\n\nrds_conn_shutdown() quiesces the transmit and receive-refill paths by\nwaiting for RDS_IN_XMIT and RDS_RECV_REFILL to be sampled clear, and\nthen runs the transport shutdown and rds_conn_path_reset().  Sampling\nthe bits clear is not the same as owning them: the moment after the\nwait_event() returns, rds_send_xmit() can re-acquire RDS_IN_XMIT (or\nrds_ib_recv_refill() can re-acquire RDS_RECV_REFILL) and run\nconcurrently with the teardown.\n\nThe sender does recheck the connection state after taking the lock,\nbut that recheck is a classic store-buffering pattern: teardown writes\nthe state and reads the bit while the sender writes the bit and reads\nthe state.  acquire_in_xmit() is only an acquire operation, so on\nweakly ordered architectures both sides can miss each other\u0027s write,\nand the transmit path then runs while the transport zeroes its rings\n(e.g. rds_ib_ring_init()) and rds_send_path_reset() rewrites the\ntransmit state under it.\n\nOracle UEK fixed the same class of crashes - a 14-year tail of\nBUG_ON()s in rds_ib_sub_signaled(), unexpected op-codes and NULL\ndereferences in rds_ib_send_cqe_handler() during failover testing -\nby making the teardown path *acquire* the fastpath bit locks instead\nof testing them (\"rds: Make sure transmit path and connection\ntear-down does not run concurrently\").  Ownership of a single word is\ndecided by RMW atomicity, so no cross-variable ordering is needed.\n\nDo the same here: take both locks before calling the transport\nshutdown, hold them across rds_conn_path_reset(), and release them\nexplicitly with a wake-up afterwards.  Both are released with\nclear_bit_unlock(), so that the ring re-initialization done by the\ntransport shutdown and the transmit state rewritten by\nrds_send_path_reset() are ordered before either bit is seen clear by\nthe next acquire_in_xmit() or acquire_refill().\n\nThe fastpath users of these bits - rds_send_xmit() and\nrds_ib_recv_refill() - are trylock style and back off while teardown\nowns the locks, so no new lock dependency is introduced for them.\nrds_tcp_reset_callbacks() is different: since the previous patch it\nacquires RDS_IN_XMIT as well, and it blocks doing so, so its wait now\nspans the teardown instead of at most one send batch.  That waiter\nruns from rds_tcp_accept_one() on the single-threaded krdsd workqueue\nand holds rds_tcp_accept_lock and t_conn_path_lock while it waits, so\na duelling SYN accepted while its path is being torn down parks\naccept processing for the duration of the teardown - for TCP bounded\nby the (up to 5 s) drain loop in rds_tcp_conn_path_shutdown().  An IB\npath\u0027s drain in rds_ib_conn_path_shutdown() has no round cap, but no\nblocking waiter either: rds_tcp_reset_callbacks() is the only blocking\nacquirer of these bits and waits only on its own TCP path, and the\nfastpaths are trylock-and-back-off on both transports, so a long IB\ndrain lengthens only that path\u0027s own quiesce.  The\nwindow is narrow: the accept-side state check has to pass before the\nteardown moves the path to RDS_CONN_DISCONNECTING.\n\nBecause krdsd is a single global workqueue, everything else queued\nthere - accept processing for other connections and network\nnamespaces, and the flush_workqueue(rds_wq) in rds_tcp_listen_stop()\nduring namespace teardown - waits behind the parked accept worker for\nthat time.  It cannot deadlock, although the waits do point at each\nother: the teardown blocks until the bit\u0027s holder releases it, and\nthe holder may be that krdsd accept worker.  The holder finishes\nwithout needing anything the teardown owns: the sync cancels\nrds_tcp_reset_callbacks() issues target cp_send_w and cp_recv_w on\nthe path\u0027s ordered cp_wq, whose only execution slot is occupied by\nthe blocked cp_down_w itself, so they are pending at most and cancel\nwithout flushing - a reliance on cp_wq being ordered that is now\nnoted next to those cancels (on \n---truncated---"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - A remote RDS/TCP peer on port 16385 drives both sides of the race: RDS ping messages make rds_recv_incoming() call rds_send_pong() and so rds_send_xmit(), and the peer\u0027s own FIN/RST reaches rds_tcp_state_change() and then rds_conn_path_drop(), which queues rds_conn_shutdown(). The damaged state is that connection\u0027s transmit state and TCP socket.\nAC:H - The attacker can start sends and teardowns at will, but the sender only overlaps the teardown if the test_bit() wait in rds_conn_shutdown() and the state recheck in rds_send_xmit() both miss each other\u0027s store. That needs a weakly ordered CPU and a narrow reordering window the attacker cannot control.\nPR:N - rds_tcp_accept_one() accepts RDS/TCP connections from any peer address with no authentication, so pings and connection drops need no credentials. A local user can also reach it without privilege, since AF_RDS socket creation has no capability check and SO_RDS_TRANSPORT autoloads rds_tcp.\nUI:N - No victim action is needed. The attacker sends the pings and resets the connection themselves.\nS:U - The race and its memory corruption stay inside the kernel\u0027s own security authority. No guest/host or other boundary is crossed.\nC:H - rds_send_xmit()/rds_tcp_xmit() can keep using tc-\u003et_sock after rds_tcp_conn_path_shutdown() has called sock_release() on it, and can keep using cp_xmit_rm while rds_send_path_reset() rewrites it. Both are use-after-free on socket and message objects, which could be groomed into kernel memory disclosure.\nI:H - The transmit path writes through a freed struct socket/sock, and through transmit and ring state (IB rings zeroed by rds_ib_ring_init()) that the teardown is rewriting at the same time. That is a heap memory-corruption primitive.\nA:H - Losing the race crashes the kernel: the commit cites BUG_ON()s in rds_ib_sub_signaled() and NULL dereferences in rds_ib_send_cqe_handler(), and the TCP path can dereference a released socket."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:13:18.938Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7f4f21e4439df30d9aca9fb3bac38191a2f34729"
        },
        {
          "url": "https://git.kernel.org/stable/c/1f900f585cbb0fbe6aa00c31c9f5bb63ee614456"
        },
        {
          "url": "https://git.kernel.org/stable/c/32e21bcf4b5b11454bf57c4bb3bf019b71512ace"
        },
        {
          "url": "https://git.kernel.org/stable/c/2e46248e375a516301884719f08b6015c79a6456"
        },
        {
          "url": "https://git.kernel.org/stable/c/7febb113795d5de5b690b208f4b0e64a5fad1201"
        },
        {
          "url": "https://git.kernel.org/stable/c/900e96c9749a06833801f60c393aa1d405ea226c"
        },
        {
          "url": "https://git.kernel.org/stable/c/1fe627e5db5c3f53a9f9f9c8a66671755d306955"
        },
        {
          "url": "https://git.kernel.org/stable/c/813f3582ac7ae9f60f917937d54660e0952d5f2d"
        }
      ],
      "title": "net/rds: acquire the fastpath locks in rds_conn_shutdown()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98069",
    "datePublished": "2026-09-25T10:24:10.887Z",
    "dateReserved": "2026-09-25T10:19:56.074Z",
    "dateUpdated": "2026-10-19T09:13:18.938Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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