fkie_cve-2022-48920
Vulnerability from fkie_nvd
Published
2024-08-22 02:15
Modified
2024-09-12 13:04
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: get rid of warning on transaction commit when using flushoncommit When using the flushoncommit mount option, during almost every transaction commit we trigger a warning from __writeback_inodes_sb_nr(): $ cat fs/fs-writeback.c: (...) static void __writeback_inodes_sb_nr(struct super_block *sb, ... { (...) WARN_ON(!rwsem_is_locked(&sb->s_umount)); (...) } (...) The trace produced in dmesg looks like the following: [947.473890] WARNING: CPU: 5 PID: 930 at fs/fs-writeback.c:2610 __writeback_inodes_sb_nr+0x7e/0xb3 [947.481623] Modules linked in: nfsd nls_cp437 cifs asn1_decoder cifs_arc4 fscache cifs_md4 ipmi_ssif [947.489571] CPU: 5 PID: 930 Comm: btrfs-transacti Not tainted 95.16.3-srb-asrock-00001-g36437ad63879 #186 [947.497969] RIP: 0010:__writeback_inodes_sb_nr+0x7e/0xb3 [947.502097] Code: 24 10 4c 89 44 24 18 c6 (...) [947.519760] RSP: 0018:ffffc90000777e10 EFLAGS: 00010246 [947.523818] RAX: 0000000000000000 RBX: 0000000000963300 RCX: 0000000000000000 [947.529765] RDX: 0000000000000000 RSI: 000000000000fa51 RDI: ffffc90000777e50 [947.535740] RBP: ffff888101628a90 R08: ffff888100955800 R09: ffff888100956000 [947.541701] R10: 0000000000000002 R11: 0000000000000001 R12: ffff888100963488 [947.547645] R13: ffff888100963000 R14: ffff888112fb7200 R15: ffff888100963460 [947.553621] FS: 0000000000000000(0000) GS:ffff88841fd40000(0000) knlGS:0000000000000000 [947.560537] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [947.565122] CR2: 0000000008be50c4 CR3: 000000000220c000 CR4: 00000000001006e0 [947.571072] Call Trace: [947.572354] <TASK> [947.573266] btrfs_commit_transaction+0x1f1/0x998 [947.576785] ? start_transaction+0x3ab/0x44e [947.579867] ? schedule_timeout+0x8a/0xdd [947.582716] transaction_kthread+0xe9/0x156 [947.585721] ? btrfs_cleanup_transaction.isra.0+0x407/0x407 [947.590104] kthread+0x131/0x139 [947.592168] ? set_kthread_struct+0x32/0x32 [947.595174] ret_from_fork+0x22/0x30 [947.597561] </TASK> [947.598553] ---[ end trace 644721052755541c ]--- This is because we started using writeback_inodes_sb() to flush delalloc when committing a transaction (when using -o flushoncommit), in order to avoid deadlocks with filesystem freeze operations. This change was made by commit ce8ea7cc6eb313 ("btrfs: don't call btrfs_start_delalloc_roots in flushoncommit"). After that change we started producing that warning, and every now and then a user reports this since the warning happens too often, it spams dmesg/syslog, and a user is unsure if this reflects any problem that might compromise the filesystem's reliability. We can not just lock the sb->s_umount semaphore before calling writeback_inodes_sb(), because that would at least deadlock with filesystem freezing, since at fs/super.c:freeze_super() sync_filesystem() is called while we are holding that semaphore in write mode, and that can trigger a transaction commit, resulting in a deadlock. It would also trigger the same type of deadlock in the unmount path. Possibly, it could also introduce some other locking dependencies that lockdep would report. To fix this call try_to_writeback_inodes_sb() instead of writeback_inodes_sb(), because that will try to read lock sb->s_umount and then will only call writeback_inodes_sb() if it was able to lock it. This is fine because the cases where it can't read lock sb->s_umount are during a filesystem unmount or during a filesystem freeze - in those cases sb->s_umount is write locked and sync_filesystem() is called, which calls writeback_inodes_sb(). In other words, in all cases where we can't take a read lock on sb->s_umount, writeback is already being triggered elsewhere. An alternative would be to call btrfs_start_delalloc_roots() with a number of pages different from LONG_MAX, for example matching the number of delalloc bytes we currently have, in ---truncated---
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/850a77c999b81dd2724efd2684068d6f90db8c16Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a0f0cf8341e34e5d2265bfd3a7ad68342da1e2aaPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e4d044dbffcd570351f21c747fc77ff90aed7f2ePatch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 5.17
linux linux_kernel 5.17
linux linux_kernel 5.17
linux linux_kernel 5.17


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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: get rid of warning on transaction commit when using flushoncommit\n\nWhen using the flushoncommit mount option, during almost every transaction\ncommit we trigger a warning from __writeback_inodes_sb_nr():\n\n  $ cat fs/fs-writeback.c:\n  (...)\n  static void __writeback_inodes_sb_nr(struct super_block *sb, ...\n  {\n        (...)\n        WARN_ON(!rwsem_is_locked(\u0026sb-\u003es_umount));\n        (...)\n  }\n  (...)\n\nThe trace produced in dmesg looks like the following:\n\n  [947.473890] WARNING: CPU: 5 PID: 930 at fs/fs-writeback.c:2610 __writeback_inodes_sb_nr+0x7e/0xb3\n  [947.481623] Modules linked in: nfsd nls_cp437 cifs asn1_decoder cifs_arc4 fscache cifs_md4 ipmi_ssif\n  [947.489571] CPU: 5 PID: 930 Comm: btrfs-transacti Not tainted 95.16.3-srb-asrock-00001-g36437ad63879 #186\n  [947.497969] RIP: 0010:__writeback_inodes_sb_nr+0x7e/0xb3\n  [947.502097] Code: 24 10 4c 89 44 24 18 c6 (...)\n  [947.519760] RSP: 0018:ffffc90000777e10 EFLAGS: 00010246\n  [947.523818] RAX: 0000000000000000 RBX: 0000000000963300 RCX: 0000000000000000\n  [947.529765] RDX: 0000000000000000 RSI: 000000000000fa51 RDI: ffffc90000777e50\n  [947.535740] RBP: ffff888101628a90 R08: ffff888100955800 R09: ffff888100956000\n  [947.541701] R10: 0000000000000002 R11: 0000000000000001 R12: ffff888100963488\n  [947.547645] R13: ffff888100963000 R14: ffff888112fb7200 R15: ffff888100963460\n  [947.553621] FS:  0000000000000000(0000) GS:ffff88841fd40000(0000) knlGS:0000000000000000\n  [947.560537] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  [947.565122] CR2: 0000000008be50c4 CR3: 000000000220c000 CR4: 00000000001006e0\n  [947.571072] Call Trace:\n  [947.572354]  \u003cTASK\u003e\n  [947.573266]  btrfs_commit_transaction+0x1f1/0x998\n  [947.576785]  ? start_transaction+0x3ab/0x44e\n  [947.579867]  ? schedule_timeout+0x8a/0xdd\n  [947.582716]  transaction_kthread+0xe9/0x156\n  [947.585721]  ? btrfs_cleanup_transaction.isra.0+0x407/0x407\n  [947.590104]  kthread+0x131/0x139\n  [947.592168]  ? set_kthread_struct+0x32/0x32\n  [947.595174]  ret_from_fork+0x22/0x30\n  [947.597561]  \u003c/TASK\u003e\n  [947.598553] ---[ end trace 644721052755541c ]---\n\nThis is because we started using writeback_inodes_sb() to flush delalloc\nwhen committing a transaction (when using -o flushoncommit), in order to\navoid deadlocks with filesystem freeze operations. This change was made\nby commit ce8ea7cc6eb313 (\"btrfs: don\u0027t call btrfs_start_delalloc_roots\nin flushoncommit\"). After that change we started producing that warning,\nand every now and then a user reports this since the warning happens too\noften, it spams dmesg/syslog, and a user is unsure if this reflects any\nproblem that might compromise the filesystem\u0027s reliability.\n\nWe can not just lock the sb-\u003es_umount semaphore before calling\nwriteback_inodes_sb(), because that would at least deadlock with\nfilesystem freezing, since at fs/super.c:freeze_super() sync_filesystem()\nis called while we are holding that semaphore in write mode, and that can\ntrigger a transaction commit, resulting in a deadlock. It would also\ntrigger the same type of deadlock in the unmount path. Possibly, it could\nalso introduce some other locking dependencies that lockdep would report.\n\nTo fix this call try_to_writeback_inodes_sb() instead of\nwriteback_inodes_sb(), because that will try to read lock sb-\u003es_umount\nand then will only call writeback_inodes_sb() if it was able to lock it.\nThis is fine because the cases where it can\u0027t read lock sb-\u003es_umount\nare during a filesystem unmount or during a filesystem freeze - in those\ncases sb-\u003es_umount is write locked and sync_filesystem() is called, which\ncalls writeback_inodes_sb(). In other words, in all cases where we can\u0027t\ntake a read lock on sb-\u003es_umount, writeback is already being triggered\nelsewhere.\n\nAn alternative would be to call btrfs_start_delalloc_roots() with a\nnumber of pages different from LONG_MAX, for example matching the number\nof delalloc bytes we currently have, in \n---truncated---"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: elimina la advertencia en el commit de transacci\u00f3n cuando se usa fluoncommit Cuando se usa la opci\u00f3n de montaje fluoncommit, durante casi cada commit de transacci\u00f3n activamos una advertencia de __writeback_inodes_sb_nr(): $ cat fs/fs -writeback.c: (...) vac\u00edo est\u00e1tico __writeback_inodes_sb_nr(struct super_block *sb, ... { (...) WARN_ON(!rwsem_is_locked(\u0026amp;sb-\u0026gt;s_umount)); (...) } (... ) La traza producida en dmesg se parece a la siguiente: [947.473890] ADVERTENCIA: CPU: 5 PID: 930 en fs/fs-writeback.c:2610 __writeback_inodes_sb_nr+0x7e/0xb3 [947.481623] M\u00f3dulos vinculados en: nfsd nls_cp437 cifs asn1_decoder s_arc4 fscache cifs_md4 ipmi_ssif [947.489571] CPU: 5 PID: 930 Comm: btrfs-transacti No contaminado 95.16.3-srb-asrock-00001-g36437ad63879 #186 [947.497969] RIP: __writeback_inodes_sb_nr +0x7e/0xb3 [947.502097] C\u00f3digo: 24 10 4c 89 44 24 18 c6 (...) [947.519760] RSP: 0018:ffffc90000777e10 EFLAGS: 00010246 [947.523818] RAX: 0000000000000000 RBX: 0000000000963300 X: 0000000000000000 [947.529765] RDX: 0000000000000000 RSI: 000000000000fa51 RDI: ffffc90000777e50 [947.535740] RBP : ffff888101628a90 R08: ffff888100955800 R09: ffff888100956000 [947.541701] R10: 00000000000000002 R11: 0000000000000001 R12: ffff88810096 3488 [947.547645] R13: ffff888100963000 R14: ffff888112fb7200 R15: ffff888100963460 [947.553621] FS: 0000000000000000(0000) GS:ffff88841fd40 000(0000) knlGS:0000000000000000 [947.560537] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [947.565122] CR2: 0000000008be50c4 CR3: 000000000220c000 CR4: 00000000001006e 0 [947.571072] Seguimiento de llamadas: [947.572354]  [947.573266] btrfs_commit_transaction+0x1f1/0x998 [947.576785] ? start_transaction+0x3ab/0x44e [947.579867] ? Schedule_timeout+0x8a/0xdd [947.582716] transacci\u00f3n_kthread+0xe9/0x156 [947.585721] ? btrfs_cleanup_transaction.isra.0+0x407/0x407 [947.590104] kthread+0x131/0x139 [947.592168] ? set_kthread_struct+0x32/0x32 [947.595174] ret_from_fork+0x22/0x30 [947.597561]  [947.598553] ---[ end trace 644721052755541c ]--- Esto se debe a que comenzamos a usar writeback_inodes_sb() para vaciar delalloc cuando cometer una transacci\u00f3n (cuando se usa -o fluoncommit), para evitar interbloqueos con las operaciones de congelaci\u00f3n del sistema de archivos. Este cambio se realiz\u00f3 mediante el commit ce8ea7cc6eb313 (\"btrfs: no llame a btrfs_start_delalloc_roots en flowoncommit\"). Despu\u00e9s de ese cambio, comenzamos a producir esa advertencia y, de vez en cuando, un usuario informa esto ya que la advertencia ocurre con demasiada frecuencia, env\u00eda spam a dmesg/syslog y el usuario no est\u00e1 seguro de si esto refleja alg\u00fan problema que pueda comprometer la confiabilidad del sistema de archivos. No podemos simplemente bloquear el sem\u00e1foro sb-\u0026gt;s_umount antes de llamar a writeback_inodes_sb(), porque eso al menos bloquear\u00eda el sistema de archivos, ya que en fs/super.c:freeze_super() se llama a sync_filesystem() mientras mantenemos ese sem\u00e1foro en modo de escritura, y eso puede desencadenar un commit de transacci\u00f3n, lo que resulta en un punto muerto. Tambi\u00e9n desencadenar\u00eda el mismo tipo de punto muerto en la ruta de desmontaje. Posiblemente, tambi\u00e9n podr\u00eda introducir algunas otras dependencias de bloqueo que lockdep informar\u00eda. Para solucionar este problema, llame a try_to_writeback_inodes_sb() en lugar de writeback_inodes_sb(), porque intentar\u00e1 leer el bloqueo sb-\u0026gt;s_umount y luego solo llamar\u00e1 a writeback_inodes_sb() si pudo bloquearlo. Esto est\u00e1 bien porque los casos en los que no puede leer el bloqueo sb-\u0026gt;s_umount son durante un desmontaje del sistema de archivos o durante una congelaci\u00f3n del sistema de archivos; en esos casos, sb-\u0026gt;s_umount est\u00e1 bloqueado contra escritura y se llama a sync_filesystem(), que llama a writeback_inodes_sb() . En otras palabras, en todos los casos en los que no podemos adoptar un bloqueo de lectura en sb-\u0026gt;s_umount, la reescritura ya se est\u00e1 activando en otro lugar. ---truncado---"
    }
  ],
  "id": "CVE-2022-48920",
  "lastModified": "2024-09-12T13:04:26.640",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2024-08-22T02:15:06.080",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/850a77c999b81dd2724efd2684068d6f90db8c16"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/a0f0cf8341e34e5d2265bfd3a7ad68342da1e2aa"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/e4d044dbffcd570351f21c747fc77ff90aed7f2e"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-667"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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