CVE-2025-38358

Estado: AnalizadaMedia (4.7)—

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix race between async reclaim worker and close_ctree()

Syzbot reported an assertion failure due to an attempt to add a delayed iput after we have set BTRFS_FS_STATE_NO_DELAYED_IPUT in the fs_info state:

This can happen due to a race with the async reclaim worker like this:

Fix this by setting BTRFS_FS_STATE_NO_DELAYED_IPUT only after we wait for the async reclaim workers to finish, after we call cancel_work_sync() for them at close_ctree(), and by running delayed iputs after wait for the reclaim workers to finish and before setting the bit.

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This race was recently introduced by commit 19e60b2a95f5 ("btrfs: add extra warning if delayed iput is added when it's not allowed"). Without the new validation at btrfs_add_delayed_iput(), ---truncated---

Detalles técnicos trazas, registros y código del informe original

  WARNING: CPU: 0 PID: 65 at fs/btrfs/inode.c:3420 btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420
  Modules linked in:
  CPU: 0 UID: 0 PID: 65 Comm: kworker/u8:4 Not tainted 6.15.0-next-20250530-syzkaller #0 PREEMPT(full)
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
  Workqueue: btrfs-endio-write btrfs_work_helper
  RIP: 0010:btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420
  Code: 4e ad 5d (...)
  RSP: 0018:ffffc9000213f780 EFLAGS: 00010293
  RAX: ffffffff83c635b7 RBX: ffff888058920000 RCX: ffff88801c769e00
  RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000000
  RBP: 0000000000000001 R08: ffff888058921b67 R09: 1ffff1100b12436c
  R10: dffffc0000000000 R11: ffffed100b12436d R12: 0000000000000001
  R13: dffffc0000000000 R14: ffff88807d748000 R15: 0000000000000100
  FS:  0000000000000000(0000) GS:ffff888125c53000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00002000000bd038 CR3: 000000006a142000 CR4: 00000000003526f0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   <TASK>
   btrfs_put_ordered_extent+0x19f/0x470 fs/btrfs/ordered-data.c:635
   btrfs_finish_one_ordered+0x11d8/0x1b10 fs/btrfs/inode.c:3312
   btrfs_work_helper+0x399/0xc20 fs/btrfs/async-thread.c:312
   process_one_work kernel/workqueue.c:3238 [inline]
   process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
   worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
   kthread+0x70e/0x8a0 kernel/kthread.c:464
   ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
   </TASK>

1) The async metadata reclaim worker enters shrink_delalloc(), which calls
   btrfs_start_delalloc_roots() with an nr_pages argument that has a value
   less than LONG_MAX, and that in turn enters start_delalloc_inodes(),
   which sets the local variable 'full_flush' to false because
   wbc->nr_to_write is less than LONG_MAX;

2) There it finds inode X in a root's delalloc list, grabs a reference for
   inode X (with igrab()), and triggers writeback for it with
   filemap_fdatawrite_wbc(), which creates an ordered extent for inode X;

3) The unmount sequence starts from another task, we enter close_ctree()
   and we flush the workqueue fs_info->endio_write_workers, which waits
   for the ordered extent for inode X to complete and when dropping the
   last reference of the ordered extent, with btrfs_put_ordered_extent(),
   when we call btrfs_add_delayed_iput() we don't add the inode to the
   list of delayed iputs because it has a refcount of 2, so we decrement
   it to 1 and return;

4) Shortly after at close_ctree() we call btrfs_run_delayed_iputs() which
   runs all delayed iputs, and then we set BTRFS_FS_STATE_NO_DELAYED_IPUT
   in the fs_info state;

5) The async reclaim worker, after calling filemap_fdatawrite_wbc(), now
   calls btrfs_add_delayed_iput() for inode X and there we trigger an
   assertion failure since the fs_info state has the flag
   BTRFS_FS_STATE_NO_DELAYED_IPUT set.

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Puntuación base: 4.7

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.10%
Percentil entre todas las CVEs puntuadas: 1
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-362

Referencias

JSON original (NVD)

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{
  "id": "CVE-2025-38358",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 4.7,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 1
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "19e60b2a95f5d6b77d972c7bec35a11e70fd118c",
              "lessThan": "4693cda2c06039c875f2eef0123b22340c34bfa0",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "19e60b2a95f5d6b77d972c7bec35a11e70fd118c",
              "lessThan": "a26bf338cdad3643a6e7c3d78a172baadba15c1a",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/btrfs/disk-io.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.15",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.15.5",
              "versionType": "semver",
              "lessThanOrEqual": "6.15.*"
            },
            {
              "status": "unaffected",
              "version": "6.16",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "fs/btrfs/disk-io.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2025-07-25T13:15:24.573",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/4693cda2c06039c875f2eef0123b22340c34bfa0",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a26bf338cdad3643a6e7c3d78a172baadba15c1a",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-362"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix race between async reclaim worker and close_ctree()\n\nSyzbot reported an assertion failure due to an attempt to add a delayed\niput after we have set BTRFS_FS_STATE_NO_DELAYED_IPUT in the fs_info\nstate:\n\n  WARNING: CPU: 0 PID: 65 at fs/btrfs/inode.c:3420 btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420\n  Modules linked in:\n  CPU: 0 UID: 0 PID: 65 Comm: kworker/u8:4 Not tainted 6.15.0-next-20250530-syzkaller #0 PREEMPT(full)\n  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025\n  Workqueue: btrfs-endio-write btrfs_work_helper\n  RIP: 0010:btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420\n  Code: 4e ad 5d (...)\n  RSP: 0018:ffffc9000213f780 EFLAGS: 00010293\n  RAX: ffffffff83c635b7 RBX: ffff888058920000 RCX: ffff88801c769e00\n  RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000000\n  RBP: 0000000000000001 R08: ffff888058921b67 R09: 1ffff1100b12436c\n  R10: dffffc0000000000 R11: ffffed100b12436d R12: 0000000000000001\n  R13: dffffc0000000000 R14: ffff88807d748000 R15: 0000000000000100\n  FS:  0000000000000000(0000) GS:ffff888125c53000(0000) knlGS:0000000000000000\n  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  CR2: 00002000000bd038 CR3: 000000006a142000 CR4: 00000000003526f0\n  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\n  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\n  Call Trace:\n   <TASK>\n   btrfs_put_ordered_extent+0x19f/0x470 fs/btrfs/ordered-data.c:635\n   btrfs_finish_one_ordered+0x11d8/0x1b10 fs/btrfs/inode.c:3312\n   btrfs_work_helper+0x399/0xc20 fs/btrfs/async-thread.c:312\n   process_one_work kernel/workqueue.c:3238 [inline]\n   process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321\n   worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402\n   kthread+0x70e/0x8a0 kernel/kthread.c:464\n   ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148\n   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245\n   </TASK>\n\nThis can happen due to a race with the async reclaim worker like this:\n\n1) The async metadata reclaim worker enters shrink_delalloc(), which calls\n   btrfs_start_delalloc_roots() with an nr_pages argument that has a value\n   less than LONG_MAX, and that in turn enters start_delalloc_inodes(),\n   which sets the local variable 'full_flush' to false because\n   wbc->nr_to_write is less than LONG_MAX;\n\n2) There it finds inode X in a root's delalloc list, grabs a reference for\n   inode X (with igrab()), and triggers writeback for it with\n   filemap_fdatawrite_wbc(), which creates an ordered extent for inode X;\n\n3) The unmount sequence starts from another task, we enter close_ctree()\n   and we flush the workqueue fs_info->endio_write_workers, which waits\n   for the ordered extent for inode X to complete and when dropping the\n   last reference of the ordered extent, with btrfs_put_ordered_extent(),\n   when we call btrfs_add_delayed_iput() we don't add the inode to the\n   list of delayed iputs because it has a refcount of 2, so we decrement\n   it to 1 and return;\n\n4) Shortly after at close_ctree() we call btrfs_run_delayed_iputs() which\n   runs all delayed iputs, and then we set BTRFS_FS_STATE_NO_DELAYED_IPUT\n   in the fs_info state;\n\n5) The async reclaim worker, after calling filemap_fdatawrite_wbc(), now\n   calls btrfs_add_delayed_iput() for inode X and there we trigger an\n   assertion failure since the fs_info state has the flag\n   BTRFS_FS_STATE_NO_DELAYED_IPUT set.\n\nFix this by setting BTRFS_FS_STATE_NO_DELAYED_IPUT only after we wait for\nthe async reclaim workers to finish, after we call cancel_work_sync() for\nthem at close_ctree(), and by running delayed iputs after wait for the\nreclaim workers to finish and before setting the bit.\n\nThis race was recently introduced by commit 19e60b2a95f5 (\"btrfs: add\nextra warning if delayed iput is added when it's not allowed\"). Without\nthe new validation at btrfs_add_delayed_iput(), \n---truncated---"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: corrección de la ejecución entre el trabajador de recuperación asíncrono y close_ctree() Syzbot informó de un error de aserción debido a un intento de agregar una entrada retrasada después de que hayamos establecido BTRFS_FS_STATE_NO_DELAYED_IPUT en el estado WARNING: CPU: 0 PID: 65 at fs/btrfs/inode.c:3420 btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420 Modules linked in: CPU: 0 UID: 0 PID: 65 Comm: kworker/u8:4 Not tainted 6.15.0-next-20250530-syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: btrfs-endio-write btrfs_work_helper RIP: 0010:btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420 Code: 4e ad 5d (...) RSP: 0018:ffffc9000213f780 EFLAGS: 00010293 RAX: ffffffff83c635b7 RBX: ffff888058920000 RCX: ffff88801c769e00 RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000000 RBP: 0000000000000001 R08: ffff888058921b67 R09: 1ffff1100b12436c R10: dffffc0000000000 R11: ffffed100b12436d R12: 0000000000000001 R13: dffffc0000000000 R14: ffff88807d748000 R15: 0000000000000100 FS: 0000000000000000(0000) GS:ffff888125c53000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 ---truncado--- Call Trace:  btrfs_put_ordered_extent+0x19f/0x470 fs/btrfs/ordered-data.c:635 btrfs_finish_one_ordered+0x11d8/0x1b10 fs/btrfs/inode.c:3312 btrfs_work_helper+0x399/0xc20 fs/btrfs/async-thread.c:312 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245  Esto puede suceder debido a una ejecución con el trabajador de recuperación asíncrono como este: 1) El trabajador de recuperación de metadatos asíncrono ingresa a shrink_delalloc(), que llama a btrfs_start_delalloc_roots() con un argumento nr_pages que tiene un valor menor que LONG_MAX, y que a su vez ingresa a start_delalloc_inodes(), que establece la variable local 'full_flush' en falso porque wbc-&gt;nr_to_write es menor que LONG_MAX; 2) Allí encuentra el inodo X en una lista delalloc de la raíz, toma una referencia para el inodo X (con igrab()), y activa la escritura diferida para él con filemap_fdatawrite_wbc(), que crea una extensión ordenada para el inodo X; 3) La secuencia de desmontaje comienza desde otra tarea, ingresamos close_ctree() y limpiamos la cola de trabajo fs_info-&gt;endio_write_workers, que espera a que se complete la extensión ordenada para el inodo X y cuando eliminamos la última referencia de la extensión ordenada, con btrfs_put_ordered_extent(), cuando llamamos a btrfs_add_delayed_iput() no agregamos el inodo a la lista de entradas retrasadas porque tiene un refcount de 2, por lo que lo decrementamos a 1 y regresamos; 4) Poco después, en close_ctree(), llamamos a btrfs_run_delayed_iputs(), que ejecuta todas las entradas retrasadas, y luego establecemos BTRFS_FS_STATE_NO_DELAYED_IPUT en el estado fs_info. 5) El trabajador de recuperación asíncrono, después de llamar a filemap_fdatawrite_wbc(), ahora llama a btrfs_add_delayed_iput() para el inodo X y allí desencadenamos un error de aserción, ya que el estado fs_info tiene el indicador BTRFS_FS_STATE_NO_DELAYED_IPUT establecido. Solucione esto estableciendo BTRFS_FS_STATE_NO_DELAYED_IPUT solo después de esperar a que finalicen los trabajadores de recuperación asíncronos, después de llamar a cancel_work_sync() para ellos en close_ctree(), y ejecutando las entradas retrasadas después de esperar a que finalicen los trabajadores de recuperación y antes de establecer el bit. Esta ejecución se introdujo recientemente mediante el commit 19e60b2a95f5 (\"btrfs: añadir una advertencia adicional si se añade una entrada retardada cuando no está permitida\"). Sin la nueva validación en btrfs_add_delayed_iput(), ---truncado---"
    }
  ],
  "lastModified": "2026-06-17T09:16:42.003",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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}