CVE-2026-90171 (GCVE-0-2026-90171)
Vulnerability from cvelistv5
Published
2026-09-17 16:06
Modified
2026-10-19 08:59
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: smbdirect: release pending child sockets outside the handler lock smbdirect_socket_destroy() releases the listener's pending/ready child sockets while still holding the listener's handler lock, the &id_priv->handler_mutex taken via rdma_lock_handler(), not sc->listen.lock, and before the listener's own rdma_destroy_id(). That ordering has one real consequence and one cosmetic one. The real one: smbdirect_socket_release() drops the child's last reference, which destroys the child's cm_id. Doing that before the listener's rdma_destroy_id() lets _cma_cancel_listens(), running from the listener's _destroy_id(), walk an already freed child id_priv, which KASAN catches as a slab-use-after-free during listener shutdown: [ 4758.909130] BUG: KASAN: slab-use-after-free in __mutex_lock+0x1469/0x1560 [ 4758.911450] Read of size 1 at addr ffff88821c381db4 by task ksmbd.control/1652 [ 4758.913262] Call Trace: [ 4758.913267] <TASK> [ 4758.913299] __mutex_lock+0x1469/0x1560 [ 4758.913408] _cma_cancel_listens+0x312/0x3b0 [ 4758.913413] _destroy_id+0x363/0xee0 [ 4758.913417] smbdirect_socket_destroy_sync+0x17d5/0x2440 [ 4758.913443] smbdirect_socket_release+0x124/0x230 [ 4758.913451] ksmbd_rdma_stop_listening+0x9f/0x190 [ 4758.913457] ksmbd_conn_transport_destroy+0x65/0x3c0 [ 4758.913463] kill_server_store+0x1fb/0x2b0 [ 4758.913501] kernfs_fop_write_iter+0x349/0x4d0 [ 4758.913507] vfs_write+0x5e7/0xc70 [ 4758.913528] ksys_write+0x12a/0x210 [ 4758.913541] do_syscall_64+0x135/0x460 [ 4758.913555] entry_SYSCALL_64_after_hwframe+0x77/0x7f The cosmetic one: releasing a child recurses into smbdirect_socket_destroy(), which takes the child's own rdma_lock_handler() lock nested under the listener's. The listener's and the child's cm_id are always different instances, so this cannot deadlock for real; the CM core itself nests a new connection id's handler_mutex under the listening id's in cma_ib_req_handler(). But lockdep only sees one lock class, reports possible recursive locking, and then disables itself, hiding real locking bugs for the rest of the run: [ 2424.579653] WARNING: possible recursive locking detected [ 2424.581180] 7.1.0-next-20260623+ #89 Not tainted [ 2424.582548] -------------------------------------------- [ 2424.584500] ksmbd.control/8854 is trying to acquire lock: [ 2424.586817] ffff888102303c20 (&id_priv->handler_mutex){+.+.}-{4:4}, at: smbdirect_socket_destroy_sync+0xc39/0x2440 [ 2424.590590] [ 2424.590590] but task is already holding lock: [ 2424.591601] ffff888102046c20 (&id_priv->handler_mutex){+.+.}-{4:4}, at: smbdirect_socket_destroy_sync+0xc39/0x2440 [ 2424.594178] [ 2424.594178] other info that might help us debug this: [ 2424.596634] Possible unsafe locking scenario: [ 2424.596634] [ 2424.598841] CPU0 [ 2424.599765] ---- [ 2424.600695] lock(&id_priv->handler_mutex); [ 2424.601836] lock(&id_priv->handler_mutex); [ 2424.602590] [ 2424.602590] *** DEADLOCK *** [ 2424.602590] [ 2424.604512] May be due to missing lock nesting notation Splice the pending/ready children onto a local list under the listener's listen.lock, while the handler lock is held so a concurrent CM CONNECT_REQUEST cannot add more, but defer the actual smbdirect_socket_release() calls until after the listener's cm_id has been destroyed and its handler lock dropped. The children are independent sockets whose teardown needs neither the listener's handler lock nor its cm_id. Found with ksmbdzzer [2], a KSMBD fuzzer that drives libFuzzer with a kcov-dataflow [1] coverage vector: it folds each instrumented comparison/argument's runtime operand value together with its PC (the default arm mixes them as pc⊕val) so that a new operand value at a known site counts as new coverage. [1] https://lwn.net/Articles/1077606/ [2] https://github.com/yskzalloc/kcov-dataflow
References
Impacted products
Vendor Product Version
Linux Linux Version: dc691b91ad1677def14582a279e56fd943b52f94
Version: dc691b91ad1677def14582a279e56fd943b52f94
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/smbdirect/socket.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "8ea83ef0c40ec4463695e22bc9ae43e29bcfede7",
              "status": "affected",
              "version": "dc691b91ad1677def14582a279e56fd943b52f94",
              "versionType": "git"
            },
            {
              "lessThan": "db82fbe4bb68e68e4aef00ef5b79f92991d8ef8e",
              "status": "affected",
              "version": "dc691b91ad1677def14582a279e56fd943b52f94",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/smbdirect/socket.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: smbdirect: release pending child sockets outside the handler lock\n\nsmbdirect_socket_destroy() releases the listener\u0027s pending/ready child\nsockets while still holding the listener\u0027s handler lock, the\n\u0026id_priv-\u003ehandler_mutex taken via rdma_lock_handler(), not\nsc-\u003elisten.lock, and before the listener\u0027s own rdma_destroy_id().\nThat ordering has one real consequence and one cosmetic one.\n\nThe real one: smbdirect_socket_release() drops the child\u0027s last\nreference, which destroys the child\u0027s cm_id.  Doing that before the\nlistener\u0027s rdma_destroy_id() lets _cma_cancel_listens(), running from\nthe listener\u0027s _destroy_id(), walk an already freed child id_priv,\nwhich KASAN catches as a slab-use-after-free during listener shutdown:\n\n[ 4758.909130] BUG: KASAN: slab-use-after-free in __mutex_lock+0x1469/0x1560\n[ 4758.911450] Read of size 1 at addr ffff88821c381db4 by task ksmbd.control/1652\n[ 4758.913262] Call Trace:\n[ 4758.913267]  \u003cTASK\u003e\n[ 4758.913299]  __mutex_lock+0x1469/0x1560\n[ 4758.913408]  _cma_cancel_listens+0x312/0x3b0\n[ 4758.913413]  _destroy_id+0x363/0xee0\n[ 4758.913417]  smbdirect_socket_destroy_sync+0x17d5/0x2440\n[ 4758.913443]  smbdirect_socket_release+0x124/0x230\n[ 4758.913451]  ksmbd_rdma_stop_listening+0x9f/0x190\n[ 4758.913457]  ksmbd_conn_transport_destroy+0x65/0x3c0\n[ 4758.913463]  kill_server_store+0x1fb/0x2b0\n[ 4758.913501]  kernfs_fop_write_iter+0x349/0x4d0\n[ 4758.913507]  vfs_write+0x5e7/0xc70\n[ 4758.913528]  ksys_write+0x12a/0x210\n[ 4758.913541]  do_syscall_64+0x135/0x460\n[ 4758.913555]  entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nThe cosmetic one: releasing a child recurses into\nsmbdirect_socket_destroy(), which takes the child\u0027s own\nrdma_lock_handler() lock nested under the listener\u0027s.  The listener\u0027s\nand the child\u0027s cm_id are always different instances, so this cannot\ndeadlock for real; the CM core itself nests a new connection id\u0027s\nhandler_mutex under the listening id\u0027s in cma_ib_req_handler().  But\nlockdep only sees one lock class, reports possible recursive locking,\nand then disables itself, hiding real locking bugs for the rest of the\nrun:\n\n[ 2424.579653] WARNING: possible recursive locking detected\n[ 2424.581180] 7.1.0-next-20260623+ #89 Not tainted\n[ 2424.582548] --------------------------------------------\n[ 2424.584500] ksmbd.control/8854 is trying to acquire lock:\n[ 2424.586817] ffff888102303c20 (\u0026id_priv-\u003ehandler_mutex){+.+.}-{4:4}, at: smbdirect_socket_destroy_sync+0xc39/0x2440\n[ 2424.590590]\n[ 2424.590590] but task is already holding lock:\n[ 2424.591601] ffff888102046c20 (\u0026id_priv-\u003ehandler_mutex){+.+.}-{4:4}, at: smbdirect_socket_destroy_sync+0xc39/0x2440\n[ 2424.594178]\n[ 2424.594178] other info that might help us debug this:\n[ 2424.596634]  Possible unsafe locking scenario:\n[ 2424.596634]\n[ 2424.598841]        CPU0\n[ 2424.599765]        ----\n[ 2424.600695]   lock(\u0026id_priv-\u003ehandler_mutex);\n[ 2424.601836]   lock(\u0026id_priv-\u003ehandler_mutex);\n[ 2424.602590]\n[ 2424.602590]  *** DEADLOCK ***\n[ 2424.602590]\n[ 2424.604512]  May be due to missing lock nesting notation\n\nSplice the pending/ready children onto a local list under the\nlistener\u0027s listen.lock, while the handler lock is held so a concurrent\nCM CONNECT_REQUEST cannot add more, but defer the actual\nsmbdirect_socket_release() calls until after the listener\u0027s cm_id has\nbeen destroyed and its handler lock dropped.  The children are\nindependent sockets whose teardown needs neither the listener\u0027s\nhandler lock nor its cm_id.\n\nFound with ksmbdzzer [2], a KSMBD fuzzer that drives libFuzzer with a\nkcov-dataflow [1] coverage vector: it folds each instrumented\ncomparison/argument\u0027s runtime operand value together with its PC (the\ndefault arm mixes them as pc\u2295val) so that a new operand value at a known\nsite counts as new coverage.\n\n[1] https://lwn.net/Articles/1077606/\n[2] https://github.com/yskzalloc/kcov-dataflow"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:59:08.551Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/8ea83ef0c40ec4463695e22bc9ae43e29bcfede7"
        },
        {
          "url": "https://git.kernel.org/stable/c/db82fbe4bb68e68e4aef00ef5b79f92991d8ef8e"
        }
      ],
      "title": "smb: smbdirect: release pending child sockets outside the handler lock",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90171",
    "datePublished": "2026-09-17T16:06:59.150Z",
    "dateReserved": "2026-09-11T19:38:34.790Z",
    "dateUpdated": "2026-10-19T08:59:08.551Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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