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CVE-2021-46987 (GCVE-0-2021-46987)

Vulnerability from cvelistv5 – Published: 2024-02-28 08:13 – Updated: 2026-05-23 15:18
VLAI
Title
btrfs: fix deadlock when cloning inline extents and using qgroups
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix deadlock when cloning inline extents and using qgroups There are a few exceptional cases where cloning an inline extent needs to copy the inline extent data into a page of the destination inode. When this happens, we end up starting a transaction while having a dirty page for the destination inode and while having the range locked in the destination's inode iotree too. Because when reserving metadata space for a transaction we may need to flush existing delalloc in case there is not enough free space, we have a mechanism in place to prevent a deadlock, which was introduced in commit 3d45f221ce627d ("btrfs: fix deadlock when cloning inline extent and low on free metadata space"). However when using qgroups, a transaction also reserves metadata qgroup space, which can also result in flushing delalloc in case there is not enough available space at the moment. When this happens we deadlock, since flushing delalloc requires locking the file range in the inode's iotree and the range was already locked at the very beginning of the clone operation, before attempting to start the transaction. When this issue happens, stack traces like the following are reported: [72747.556262] task:kworker/u81:9 state:D stack: 0 pid: 225 ppid: 2 flags:0x00004000 [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142) [72747.556271] Call Trace: [72747.556273] __schedule+0x296/0x760 [72747.556277] schedule+0x3c/0xa0 [72747.556279] io_schedule+0x12/0x40 [72747.556284] __lock_page+0x13c/0x280 [72747.556287] ? generic_file_readonly_mmap+0x70/0x70 [72747.556325] extent_write_cache_pages+0x22a/0x440 [btrfs] [72747.556331] ? __set_page_dirty_nobuffers+0xe7/0x160 [72747.556358] ? set_extent_buffer_dirty+0x5e/0x80 [btrfs] [72747.556362] ? update_group_capacity+0x25/0x210 [72747.556366] ? cpumask_next_and+0x1a/0x20 [72747.556391] extent_writepages+0x44/0xa0 [btrfs] [72747.556394] do_writepages+0x41/0xd0 [72747.556398] __writeback_single_inode+0x39/0x2a0 [72747.556403] writeback_sb_inodes+0x1ea/0x440 [72747.556407] __writeback_inodes_wb+0x5f/0xc0 [72747.556410] wb_writeback+0x235/0x2b0 [72747.556414] ? get_nr_inodes+0x35/0x50 [72747.556417] wb_workfn+0x354/0x490 [72747.556420] ? newidle_balance+0x2c5/0x3e0 [72747.556424] process_one_work+0x1aa/0x340 [72747.556426] worker_thread+0x30/0x390 [72747.556429] ? create_worker+0x1a0/0x1a0 [72747.556432] kthread+0x116/0x130 [72747.556435] ? kthread_park+0x80/0x80 [72747.556438] ret_from_fork+0x1f/0x30 [72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs] [72747.566961] Call Trace: [72747.566964] __schedule+0x296/0x760 [72747.566968] ? finish_wait+0x80/0x80 [72747.566970] schedule+0x3c/0xa0 [72747.566995] wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs] [72747.566999] ? finish_wait+0x80/0x80 [72747.567024] lock_extent_bits+0x37/0x90 [btrfs] [72747.567047] btrfs_invalidatepage+0x299/0x2c0 [btrfs] [72747.567051] ? find_get_pages_range_tag+0x2cd/0x380 [72747.567076] __extent_writepage+0x203/0x320 [btrfs] [72747.567102] extent_write_cache_pages+0x2bb/0x440 [btrfs] [72747.567106] ? update_load_avg+0x7e/0x5f0 [72747.567109] ? enqueue_entity+0xf4/0x6f0 [72747.567134] extent_writepages+0x44/0xa0 [btrfs] [72747.567137] ? enqueue_task_fair+0x93/0x6f0 [72747.567140] do_writepages+0x41/0xd0 [72747.567144] __filemap_fdatawrite_range+0xc7/0x100 [72747.567167] btrfs_run_delalloc_work+0x17/0x40 [btrfs] [72747.567195] btrfs_work_helper+0xc2/0x300 [btrfs] [72747.567200] process_one_work+0x1aa/0x340 [72747.567202] worker_thread+0x30/0x390 [72747.567205] ? create_worker+0x1a0/0x1a0 [72747.567208] kthread+0x116/0x130 [72747.567211] ? kthread_park+0x80/0x80 [72747.567214] ret_from_fork+0x1f/0x30 [72747.569686] task:fsstress state:D stack: ---truncated---
Severity
No CVSS data available.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-02-28 21:09 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: c53e9653605dbf708f5be02902de51831be4b009 , < f8fbbd06fab9b75dcd68d850fe318ac3bc128974 (git)
Affected: c53e9653605dbf708f5be02902de51831be4b009 , < d5347827d0b4b2250cbce6eccaa1c81dc78d8651 (git)
Affected: c53e9653605dbf708f5be02902de51831be4b009 , < 96157707c0420e3d3edfe046f1cc797fee117ade (git)
Affected: c53e9653605dbf708f5be02902de51831be4b009 , < f9baa501b4fd6962257853d46ddffbc21f27e344 (git)
Affected: 36af2de520cca7c37974cc4944b47850f6c460ee (git)
Affected: 5.4.141 , < 5.5 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 5.9
Unaffected: 0 , < 5.9 (semver)
Unaffected: 5.10.241 , ≤ 5.10.* (semver)
Unaffected: 5.11.22 , ≤ 5.11.* (semver)
Unaffected: 5.12.5 , ≤ 5.12.* (semver)
Unaffected: 5.13 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix deadlock when cloning inline extents and using qgroups\n\nThere are a few exceptional cases where cloning an inline extent needs to\ncopy the inline extent data into a page of the destination inode.\n\nWhen this happens, we end up starting a transaction while having a dirty\npage for the destination inode and while having the range locked in the\ndestination\u0027s inode iotree too. Because when reserving metadata space\nfor a transaction we may need to flush existing delalloc in case there is\nnot enough free space, we have a mechanism in place to prevent a deadlock,\nwhich was introduced in commit 3d45f221ce627d (\"btrfs: fix deadlock when\ncloning inline extent and low on free metadata space\").\n\nHowever when using qgroups, a transaction also reserves metadata qgroup\nspace, which can also result in flushing delalloc in case there is not\nenough available space at the moment. When this happens we deadlock, since\nflushing delalloc requires locking the file range in the inode\u0027s iotree\nand the range was already locked at the very beginning of the clone\noperation, before attempting to start the transaction.\n\nWhen this issue happens, stack traces like the following are reported:\n\n  [72747.556262] task:kworker/u81:9   state:D stack:    0 pid:  225 ppid:     2 flags:0x00004000\n  [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142)\n  [72747.556271] Call Trace:\n  [72747.556273]  __schedule+0x296/0x760\n  [72747.556277]  schedule+0x3c/0xa0\n  [72747.556279]  io_schedule+0x12/0x40\n  [72747.556284]  __lock_page+0x13c/0x280\n  [72747.556287]  ? generic_file_readonly_mmap+0x70/0x70\n  [72747.556325]  extent_write_cache_pages+0x22a/0x440 [btrfs]\n  [72747.556331]  ? __set_page_dirty_nobuffers+0xe7/0x160\n  [72747.556358]  ? set_extent_buffer_dirty+0x5e/0x80 [btrfs]\n  [72747.556362]  ? update_group_capacity+0x25/0x210\n  [72747.556366]  ? cpumask_next_and+0x1a/0x20\n  [72747.556391]  extent_writepages+0x44/0xa0 [btrfs]\n  [72747.556394]  do_writepages+0x41/0xd0\n  [72747.556398]  __writeback_single_inode+0x39/0x2a0\n  [72747.556403]  writeback_sb_inodes+0x1ea/0x440\n  [72747.556407]  __writeback_inodes_wb+0x5f/0xc0\n  [72747.556410]  wb_writeback+0x235/0x2b0\n  [72747.556414]  ? get_nr_inodes+0x35/0x50\n  [72747.556417]  wb_workfn+0x354/0x490\n  [72747.556420]  ? newidle_balance+0x2c5/0x3e0\n  [72747.556424]  process_one_work+0x1aa/0x340\n  [72747.556426]  worker_thread+0x30/0x390\n  [72747.556429]  ? create_worker+0x1a0/0x1a0\n  [72747.556432]  kthread+0x116/0x130\n  [72747.556435]  ? kthread_park+0x80/0x80\n  [72747.556438]  ret_from_fork+0x1f/0x30\n\n  [72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs]\n  [72747.566961] Call Trace:\n  [72747.566964]  __schedule+0x296/0x760\n  [72747.566968]  ? finish_wait+0x80/0x80\n  [72747.566970]  schedule+0x3c/0xa0\n  [72747.566995]  wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs]\n  [72747.566999]  ? finish_wait+0x80/0x80\n  [72747.567024]  lock_extent_bits+0x37/0x90 [btrfs]\n  [72747.567047]  btrfs_invalidatepage+0x299/0x2c0 [btrfs]\n  [72747.567051]  ? find_get_pages_range_tag+0x2cd/0x380\n  [72747.567076]  __extent_writepage+0x203/0x320 [btrfs]\n  [72747.567102]  extent_write_cache_pages+0x2bb/0x440 [btrfs]\n  [72747.567106]  ? update_load_avg+0x7e/0x5f0\n  [72747.567109]  ? enqueue_entity+0xf4/0x6f0\n  [72747.567134]  extent_writepages+0x44/0xa0 [btrfs]\n  [72747.567137]  ? enqueue_task_fair+0x93/0x6f0\n  [72747.567140]  do_writepages+0x41/0xd0\n  [72747.567144]  __filemap_fdatawrite_range+0xc7/0x100\n  [72747.567167]  btrfs_run_delalloc_work+0x17/0x40 [btrfs]\n  [72747.567195]  btrfs_work_helper+0xc2/0x300 [btrfs]\n  [72747.567200]  process_one_work+0x1aa/0x340\n  [72747.567202]  worker_thread+0x30/0x390\n  [72747.567205]  ? create_worker+0x1a0/0x1a0\n  [72747.567208]  kthread+0x116/0x130\n  [72747.567211]  ? kthread_park+0x80/0x80\n  [72747.567214]  ret_from_fork+0x1f/0x30\n\n  [72747.569686] task:fsstress        state:D stack:    \n---truncated---"
        },
        {
          "lang": "es",
          "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: btrfs: soluciona el punto muerto al clonar extensiones en l\u00ednea y usar qgroups. Hay algunos casos excepcionales en los que la clonaci\u00f3n de una extensi\u00f3n en l\u00ednea necesita copiar los datos de la extensi\u00f3n en l\u00ednea en una p\u00e1gina del inodo de destino. Cuando esto sucede, terminamos iniciando una transacci\u00f3n mientras tenemos una p\u00e1gina sucia para el inodo de destino y tambi\u00e9n tenemos el rango bloqueado en el iotree del inodo de destino. Debido a que al reservar espacio de metadatos para una transacci\u00f3n, es posible que necesitemos vaciar la delalloc existente en caso de que no haya suficiente espacio libre, contamos con un mecanismo para evitar un punto muerto, que se introdujo en el commit 3d45f221ce627d (\"btrfs: corrige el punto muerto al clonar en l\u00ednea extensi\u00f3n y poco espacio libre para metadatos\"). Sin embargo, cuando se utilizan qgroups, una transacci\u00f3n tambi\u00e9n reserva espacio de metadatos en qgroup, lo que tambi\u00e9n puede provocar la eliminaci\u00f3n de delalloc en caso de que no haya suficiente espacio disponible en este momento. Cuando esto sucede, nos bloqueamos, ya que vaciar delalloc requiere bloquear el rango de archivos en el iotree del inodo y el rango ya estaba bloqueado al comienzo de la operaci\u00f3n de clonaci\u00f3n, antes de intentar iniciar la transacci\u00f3n. Cuando ocurre este problema, se informan seguimientos de pila como los siguientes: [72747.556262] task:kworker/u81:9 state:D stack: 0 pid: 225 ppid: 2 flags:0x00004000 [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs- 1142) [72747.556271] Seguimiento de llamadas: [72747.556273] __schedule+0x296/0x760 [72747.556277] Schedule+0x3c/0xa0 [72747.556279] io_schedule+0x12/0x40 [72747.556284] __ lock_page+0x13c/0x280 [72747.556287] ? generic_file_readonly_mmap+0x70/0x70 [72747.556325] extend_write_cache_pages+0x22a/0x440 [btrfs] [72747.556331] ? __set_page_dirty_nobuffers+0xe7/0x160 [72747.556358] ? set_extent_buffer_dirty+0x5e/0x80 [btrfs] [72747.556362] ? update_group_capacity+0x25/0x210 [72747.556366] ? cpumask_next_and+0x1a/0x20 [72747.556391] extend_writepages+0x44/0xa0 [btrfs] [72747.556394] do_writepages+0x41/0xd0 [72747.556398] __writeback_single_inode+0x39/0x2a0 [72747 .556403] writeback_sb_inodes+0x1ea/0x440 [72747.556407] __writeback_inodes_wb+0x5f/0xc0 [72747.556410 ] wb_writeback+0x235/0x2b0 [72747.556414] ? get_nr_inodes+0x35/0x50 [72747.556417] wb_workfn+0x354/0x490 [72747.556420] ? newidle_balance+0x2c5/0x3e0 [72747.556424] proceso_one_work+0x1aa/0x340 [72747.556426] trabajador_thread+0x30/0x390 [72747.556429] ? create_worker+0x1a0/0x1a0 [72747.556432] kthread+0x116/0x130 [72747.556435] ? kthread_park+0x80/0x80 [72747.556438] ret_from_fork+0x1f/0x30 [72747.566958] Cola de trabajo: btrfs-flush_delalloc btrfs_work_helper [btrfs] [72747.566961] Seguimiento de llamadas: [72747.566964] __s programar+0x296/0x760 [72747.566968] ? terminar_esperar+0x80/0x80 [72747.566970] programar+0x3c/0xa0 [72747.566995] esperar_extent_bit.constprop.68+0x13b/0x1c0 [btrfs] [72747.566999] ? Finish_wait+0x80/0x80 [72747.567024] lock_extent_bits+0x37/0x90 [btrfs] [72747.567047] btrfs_invalidatepage+0x299/0x2c0 [btrfs] [72747.567051]? find_get_pages_range_tag+0x2cd/0x380 [72747.567076] __extent_writepage+0x203/0x320 [btrfs] [72747.567102] extend_write_cache_pages+0x2bb/0x440 [btrfs] [72747.567106] ? update_load_avg+0x7e/0x5f0 [72747.567109] ? enqueue_entity+0xf4/0x6f0 [72747.567134] extend_writepages+0x44/0xa0 [btrfs] [72747.567137]? enqueue_task_fair+0x93/0x6f0 [72747.567140] do_writepages+0x41/0xd0 [72747.567144] __filemap_fdatawrite_range+0xc7/0x100 [72747.567167] btrfs_run_delalloc_work+0x17/0x40 [btrfs ] [72747.567195] btrfs_work_helper+0xc2/0x300 [btrfs] [72747.567200] proceso_one_work+0x1aa/ 0x340 [72747.567202] hilo_trabajador+0x30/0x390 [72747.567205] ? create_worker+0x1a0/0x1a0 [72747.567208] kthread+0x116/0x130 [72747.567211]? kthread_park+0x80/0x80 [72747.567214] ret_from_fork+0x1f/0x30 [72747.569686] tarea:fsstress estado:D pila: ---truncado---"
        }
      ],
      "id": "CVE-2021-46987",
      "lastModified": "2024-12-06T15:07:49.483",
      "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": "2024-02-28T09:15:37.583",
      "references": [
        {
          "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
          "tags": [
            "Patch"
          ],
          "url": "https://git.kernel.org/stable/c/96157707c0420e3d3edfe046f1cc797fee117ade"
        },
        {
          "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
          "tags": [
            "Patch"
          ],
          "url": "https://git.kernel.org/stable/c/d5347827d0b4b2250cbce6eccaa1c81dc78d8651"
        },
        {
          "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
          "tags": [
            "Patch"
          ],
          "url": "https://git.kernel.org/stable/c/f9baa501b4fd6962257853d46ddffbc21f27e344"
        },
        {
          "source": "af854a3a-2127-422b-91ae-364da2661108",
          "tags": [
            "Patch"
          ],
          "url": "https://git.kernel.org/stable/c/96157707c0420e3d3edfe046f1cc797fee117ade"
        },
        {
          "source": "af854a3a-2127-422b-91ae-364da2661108",
          "tags": [
            "Patch"
          ],
          "url": "https://git.kernel.org/stable/c/d5347827d0b4b2250cbce6eccaa1c81dc78d8651"
        },
        {
          "source": "af854a3a-2127-422b-91ae-364da2661108",
          "tags": [
            "Patch"
          ],
          "url": "https://git.kernel.org/stable/c/f9baa501b4fd6962257853d46ddffbc21f27e344"
        }
      ],
      "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "vulnStatus": "Analyzed",
      "weaknesses": [
        {
          "description": [
            {
              "lang": "en",
              "value": "CWE-667"
            }
          ],
          "source": "nvd@nist.gov",
          "type": "Primary"
        }
      ]
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "fs/btrfs/ctree.h",
                  "fs/btrfs/inode.c",
                  "fs/btrfs/ioctl.c",
                  "fs/btrfs/qgroup.c",
                  "fs/btrfs/send.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "lessThan": "f8fbbd06fab9b75dcd68d850fe318ac3bc128974",
                    "status": "affected",
                    "version": "c53e9653605dbf708f5be02902de51831be4b009",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "d5347827d0b4b2250cbce6eccaa1c81dc78d8651",
                    "status": "affected",
                    "version": "c53e9653605dbf708f5be02902de51831be4b009",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "96157707c0420e3d3edfe046f1cc797fee117ade",
                    "status": "affected",
                    "version": "c53e9653605dbf708f5be02902de51831be4b009",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "f9baa501b4fd6962257853d46ddffbc21f27e344",
                    "status": "affected",
                    "version": "c53e9653605dbf708f5be02902de51831be4b009",
                    "versionType": "git"
                  },
                  {
                    "status": "affected",
                    "version": "36af2de520cca7c37974cc4944b47850f6c460ee",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "5.5",
                    "status": "affected",
                    "version": "5.4.141",
                    "versionType": "semver"
                  }
                ]
              },
              {
                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "fs/btrfs/ctree.h",
                  "fs/btrfs/inode.c",
                  "fs/btrfs/ioctl.c",
                  "fs/btrfs/qgroup.c",
                  "fs/btrfs/send.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "5.9"
                  },
                  {
                    "lessThan": "5.9",
                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "5.10.*",
                    "status": "unaffected",
                    "version": "5.10.241",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "5.11.*",
                    "status": "unaffected",
                    "version": "5.11.22",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "5.12.*",
                    "status": "unaffected",
                    "version": "5.12.5",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "5.13",
                    "versionType": "original_commit_for_fix"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "configurations": [
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "339285D8-4F10-4D9C-81F3-10EA1F3895E4",
                    "versionEndExcluding": "5.11.22",
                    "versionStartIncluding": "5.9",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "0274929A-B36C-4F4C-AB22-30A0DD6B995B",
                    "versionEndExcluding": "5.12.5",
                    "versionStartIncluding": "5.12",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*",
                    "matchCriteriaId": "0CBAD0FC-C281-4666-AB2F-F8E6E1165DF7",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix deadlock when cloning inline extents and using qgroups\n\nThere are a few exceptional cases where cloning an inline extent needs to\ncopy the inline extent data into a page of the destination inode.\n\nWhen this happens, we end up starting a transaction while having a dirty\npage for the destination inode and while having the range locked in the\ndestination\u0027s inode iotree too. Because when reserving metadata space\nfor a transaction we may need to flush existing delalloc in case there is\nnot enough free space, we have a mechanism in place to prevent a deadlock,\nwhich was introduced in commit 3d45f221ce627d (\"btrfs: fix deadlock when\ncloning inline extent and low on free metadata space\").\n\nHowever when using qgroups, a transaction also reserves metadata qgroup\nspace, which can also result in flushing delalloc in case there is not\nenough available space at the moment. When this happens we deadlock, since\nflushing delalloc requires locking the file range in the inode\u0027s iotree\nand the range was already locked at the very beginning of the clone\noperation, before attempting to start the transaction.\n\nWhen this issue happens, stack traces like the following are reported:\n\n  [72747.556262] task:kworker/u81:9   state:D stack:    0 pid:  225 ppid:     2 flags:0x00004000\n  [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142)\n  [72747.556271] Call Trace:\n  [72747.556273]  __schedule+0x296/0x760\n  [72747.556277]  schedule+0x3c/0xa0\n  [72747.556279]  io_schedule+0x12/0x40\n  [72747.556284]  __lock_page+0x13c/0x280\n  [72747.556287]  ? generic_file_readonly_mmap+0x70/0x70\n  [72747.556325]  extent_write_cache_pages+0x22a/0x440 [btrfs]\n  [72747.556331]  ? __set_page_dirty_nobuffers+0xe7/0x160\n  [72747.556358]  ? set_extent_buffer_dirty+0x5e/0x80 [btrfs]\n  [72747.556362]  ? update_group_capacity+0x25/0x210\n  [72747.556366]  ? cpumask_next_and+0x1a/0x20\n  [72747.556391]  extent_writepages+0x44/0xa0 [btrfs]\n  [72747.556394]  do_writepages+0x41/0xd0\n  [72747.556398]  __writeback_single_inode+0x39/0x2a0\n  [72747.556403]  writeback_sb_inodes+0x1ea/0x440\n  [72747.556407]  __writeback_inodes_wb+0x5f/0xc0\n  [72747.556410]  wb_writeback+0x235/0x2b0\n  [72747.556414]  ? get_nr_inodes+0x35/0x50\n  [72747.556417]  wb_workfn+0x354/0x490\n  [72747.556420]  ? newidle_balance+0x2c5/0x3e0\n  [72747.556424]  process_one_work+0x1aa/0x340\n  [72747.556426]  worker_thread+0x30/0x390\n  [72747.556429]  ? create_worker+0x1a0/0x1a0\n  [72747.556432]  kthread+0x116/0x130\n  [72747.556435]  ? kthread_park+0x80/0x80\n  [72747.556438]  ret_from_fork+0x1f/0x30\n\n  [72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs]\n  [72747.566961] Call Trace:\n  [72747.566964]  __schedule+0x296/0x760\n  [72747.566968]  ? finish_wait+0x80/0x80\n  [72747.566970]  schedule+0x3c/0xa0\n  [72747.566995]  wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs]\n  [72747.566999]  ? finish_wait+0x80/0x80\n  [72747.567024]  lock_extent_bits+0x37/0x90 [btrfs]\n  [72747.567047]  btrfs_invalidatepage+0x299/0x2c0 [btrfs]\n  [72747.567051]  ? find_get_pages_range_tag+0x2cd/0x380\n  [72747.567076]  __extent_writepage+0x203/0x320 [btrfs]\n  [72747.567102]  extent_write_cache_pages+0x2bb/0x440 [btrfs]\n  [72747.567106]  ? update_load_avg+0x7e/0x5f0\n  [72747.567109]  ? enqueue_entity+0xf4/0x6f0\n  [72747.567134]  extent_writepages+0x44/0xa0 [btrfs]\n  [72747.567137]  ? enqueue_task_fair+0x93/0x6f0\n  [72747.567140]  do_writepages+0x41/0xd0\n  [72747.567144]  __filemap_fdatawrite_range+0xc7/0x100\n  [72747.567167]  btrfs_run_delalloc_work+0x17/0x40 [btrfs]\n  [72747.567195]  btrfs_work_helper+0xc2/0x300 [btrfs]\n  [72747.567200]  process_one_work+0x1aa/0x340\n  [72747.567202]  worker_thread+0x30/0x390\n  [72747.567205]  ? create_worker+0x1a0/0x1a0\n  [72747.567208]  kthread+0x116/0x130\n  [72747.567211]  ? kthread_park+0x80/0x80\n  [72747.567214]  ret_from_fork+0x1f/0x30\n\n  [72747.569686] task:fsstress        state:D stack:    \n---truncated---"
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: btrfs: soluciona el punto muerto al clonar extensiones en l\u00ednea y usar qgroups. Hay algunos casos excepcionales en los que la clonaci\u00f3n de una extensi\u00f3n en l\u00ednea necesita copiar los datos de la extensi\u00f3n en l\u00ednea en una p\u00e1gina del inodo de destino. Cuando esto sucede, terminamos iniciando una transacci\u00f3n mientras tenemos una p\u00e1gina sucia para el inodo de destino y tambi\u00e9n tenemos el rango bloqueado en el iotree del inodo de destino. Debido a que al reservar espacio de metadatos para una transacci\u00f3n, es posible que necesitemos vaciar la delalloc existente en caso de que no haya suficiente espacio libre, contamos con un mecanismo para evitar un punto muerto, que se introdujo en el commit 3d45f221ce627d (\"btrfs: corrige el punto muerto al clonar en l\u00ednea extensi\u00f3n y poco espacio libre para metadatos\"). Sin embargo, cuando se utilizan qgroups, una transacci\u00f3n tambi\u00e9n reserva espacio de metadatos en qgroup, lo que tambi\u00e9n puede provocar la eliminaci\u00f3n de delalloc en caso de que no haya suficiente espacio disponible en este momento. Cuando esto sucede, nos bloqueamos, ya que vaciar delalloc requiere bloquear el rango de archivos en el iotree del inodo y el rango ya estaba bloqueado al comienzo de la operaci\u00f3n de clonaci\u00f3n, antes de intentar iniciar la transacci\u00f3n. Cuando ocurre este problema, se informan seguimientos de pila como los siguientes: [72747.556262] task:kworker/u81:9 state:D stack: 0 pid: 225 ppid: 2 flags:0x00004000 [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs- 1142) [72747.556271] Seguimiento de llamadas: [72747.556273] __schedule+0x296/0x760 [72747.556277] Schedule+0x3c/0xa0 [72747.556279] io_schedule+0x12/0x40 [72747.556284] __ lock_page+0x13c/0x280 [72747.556287] ? generic_file_readonly_mmap+0x70/0x70 [72747.556325] extend_write_cache_pages+0x22a/0x440 [btrfs] [72747.556331] ? __set_page_dirty_nobuffers+0xe7/0x160 [72747.556358] ? set_extent_buffer_dirty+0x5e/0x80 [btrfs] [72747.556362] ? update_group_capacity+0x25/0x210 [72747.556366] ? cpumask_next_and+0x1a/0x20 [72747.556391] extend_writepages+0x44/0xa0 [btrfs] [72747.556394] do_writepages+0x41/0xd0 [72747.556398] __writeback_single_inode+0x39/0x2a0 [72747 .556403] writeback_sb_inodes+0x1ea/0x440 [72747.556407] __writeback_inodes_wb+0x5f/0xc0 [72747.556410 ] wb_writeback+0x235/0x2b0 [72747.556414] ? get_nr_inodes+0x35/0x50 [72747.556417] wb_workfn+0x354/0x490 [72747.556420] ? newidle_balance+0x2c5/0x3e0 [72747.556424] proceso_one_work+0x1aa/0x340 [72747.556426] trabajador_thread+0x30/0x390 [72747.556429] ? create_worker+0x1a0/0x1a0 [72747.556432] kthread+0x116/0x130 [72747.556435] ? kthread_park+0x80/0x80 [72747.556438] ret_from_fork+0x1f/0x30 [72747.566958] Cola de trabajo: btrfs-flush_delalloc btrfs_work_helper [btrfs] [72747.566961] Seguimiento de llamadas: [72747.566964] __s programar+0x296/0x760 [72747.566968] ? terminar_esperar+0x80/0x80 [72747.566970] programar+0x3c/0xa0 [72747.566995] esperar_extent_bit.constprop.68+0x13b/0x1c0 [btrfs] [72747.566999] ? Finish_wait+0x80/0x80 [72747.567024] lock_extent_bits+0x37/0x90 [btrfs] [72747.567047] btrfs_invalidatepage+0x299/0x2c0 [btrfs] [72747.567051]? find_get_pages_range_tag+0x2cd/0x380 [72747.567076] __extent_writepage+0x203/0x320 [btrfs] [72747.567102] extend_write_cache_pages+0x2bb/0x440 [btrfs] [72747.567106] ? update_load_avg+0x7e/0x5f0 [72747.567109] ? enqueue_entity+0xf4/0x6f0 [72747.567134] extend_writepages+0x44/0xa0 [btrfs] [72747.567137]? enqueue_task_fair+0x93/0x6f0 [72747.567140] do_writepages+0x41/0xd0 [72747.567144] __filemap_fdatawrite_range+0xc7/0x100 [72747.567167] btrfs_run_delalloc_work+0x17/0x40 [btrfs ] [72747.567195] btrfs_work_helper+0xc2/0x300 [btrfs] [72747.567200] proceso_one_work+0x1aa/ 0x340 [72747.567202] hilo_trabajador+0x30/0x390 [72747.567205] ? create_worker+0x1a0/0x1a0 [72747.567208] kthread+0x116/0x130 [72747.567211]? kthread_park+0x80/0x80 [72747.567214] ret_from_fork+0x1f/0x30 [72747.569686] tarea:fsstress estado:D pila: ---truncado---"
          }
        ],
        "id": "CVE-2021-46987",
        "lastModified": "2026-06-17T04:16:05.287",
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                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
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      "product_status:known_affected": "42",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: btrfs: fix deadlock when cloning inline extents and using qgroups",
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      "product_status:known_not_affected": "397",
      "product_status:recommended": "23",
      "source": "SUSE CSAF VEX",
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      "title": "SUSE CVE CVE-2021-46987",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-46987.json",
      "version": "31"
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            ],
            "title": "CVE Program Container"
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          {
            "metrics": [
              {
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                    "id": "CVE-2021-46987",
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        "cna": {
          "affected": [
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              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
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                "fs/btrfs/inode.c",
                "fs/btrfs/ioctl.c",
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                "fs/btrfs/send.c"
              ],
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              "programFiles": [
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              "versions": [
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                  "version": "5.9"
                },
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                  "status": "unaffected",
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                  "version": "5.10.241",
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                },
                {
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                  "status": "unaffected",
                  "version": "5.11.22",
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                },
                {
                  "lessThanOrEqual": "5.12.*",
                  "status": "unaffected",
                  "version": "5.12.5",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "5.13",
                  "versionType": "original_commit_for_fix"
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          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.10.241",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.11.22",
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                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix deadlock when cloning inline extents and using qgroups\n\nThere are a few exceptional cases where cloning an inline extent needs to\ncopy the inline extent data into a page of the destination inode.\n\nWhen this happens, we end up starting a transaction while having a dirty\npage for the destination inode and while having the range locked in the\ndestination\u0027s inode iotree too. Because when reserving metadata space\nfor a transaction we may need to flush existing delalloc in case there is\nnot enough free space, we have a mechanism in place to prevent a deadlock,\nwhich was introduced in commit 3d45f221ce627d (\"btrfs: fix deadlock when\ncloning inline extent and low on free metadata space\").\n\nHowever when using qgroups, a transaction also reserves metadata qgroup\nspace, which can also result in flushing delalloc in case there is not\nenough available space at the moment. When this happens we deadlock, since\nflushing delalloc requires locking the file range in the inode\u0027s iotree\nand the range was already locked at the very beginning of the clone\noperation, before attempting to start the transaction.\n\nWhen this issue happens, stack traces like the following are reported:\n\n  [72747.556262] task:kworker/u81:9   state:D stack:    0 pid:  225 ppid:     2 flags:0x00004000\n  [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142)\n  [72747.556271] Call Trace:\n  [72747.556273]  __schedule+0x296/0x760\n  [72747.556277]  schedule+0x3c/0xa0\n  [72747.556279]  io_schedule+0x12/0x40\n  [72747.556284]  __lock_page+0x13c/0x280\n  [72747.556287]  ? generic_file_readonly_mmap+0x70/0x70\n  [72747.556325]  extent_write_cache_pages+0x22a/0x440 [btrfs]\n  [72747.556331]  ? __set_page_dirty_nobuffers+0xe7/0x160\n  [72747.556358]  ? set_extent_buffer_dirty+0x5e/0x80 [btrfs]\n  [72747.556362]  ? update_group_capacity+0x25/0x210\n  [72747.556366]  ? cpumask_next_and+0x1a/0x20\n  [72747.556391]  extent_writepages+0x44/0xa0 [btrfs]\n  [72747.556394]  do_writepages+0x41/0xd0\n  [72747.556398]  __writeback_single_inode+0x39/0x2a0\n  [72747.556403]  writeback_sb_inodes+0x1ea/0x440\n  [72747.556407]  __writeback_inodes_wb+0x5f/0xc0\n  [72747.556410]  wb_writeback+0x235/0x2b0\n  [72747.556414]  ? get_nr_inodes+0x35/0x50\n  [72747.556417]  wb_workfn+0x354/0x490\n  [72747.556420]  ? newidle_balance+0x2c5/0x3e0\n  [72747.556424]  process_one_work+0x1aa/0x340\n  [72747.556426]  worker_thread+0x30/0x390\n  [72747.556429]  ? create_worker+0x1a0/0x1a0\n  [72747.556432]  kthread+0x116/0x130\n  [72747.556435]  ? kthread_park+0x80/0x80\n  [72747.556438]  ret_from_fork+0x1f/0x30\n\n  [72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs]\n  [72747.566961] Call Trace:\n  [72747.566964]  __schedule+0x296/0x760\n  [72747.566968]  ? finish_wait+0x80/0x80\n  [72747.566970]  schedule+0x3c/0xa0\n  [72747.566995]  wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs]\n  [72747.566999]  ? finish_wait+0x80/0x80\n  [72747.567024]  lock_extent_bits+0x37/0x90 [btrfs]\n  [72747.567047]  btrfs_invalidatepage+0x299/0x2c0 [btrfs]\n  [72747.567051]  ? find_get_pages_range_tag+0x2cd/0x380\n  [72747.567076]  __extent_writepage+0x203/0x320 [btrfs]\n  [72747.567102]  extent_write_cache_pages+0x2bb/0x440 [btrfs]\n  [72747.567106]  ? update_load_avg+0x7e/0x5f0\n  [72747.567109]  ? enqueue_entity+0xf4/0x6f0\n  [72747.567134]  extent_writepages+0x44/0xa0 [btrfs]\n  [72747.567137]  ? enqueue_task_fair+0x93/0x6f0\n  [72747.567140]  do_writepages+0x41/0xd0\n  [72747.567144]  __filemap_fdatawrite_range+0xc7/0x100\n  [72747.567167]  btrfs_run_delalloc_work+0x17/0x40 [btrfs]\n  [72747.567195]  btrfs_work_helper+0xc2/0x300 [btrfs]\n  [72747.567200]  process_one_work+0x1aa/0x340\n  [72747.567202]  worker_thread+0x30/0x390\n  [72747.567205]  ? create_worker+0x1a0/0x1a0\n  [72747.567208]  kthread+0x116/0x130\n  [72747.567211]  ? kthread_park+0x80/0x80\n  [72747.567214]  ret_from_fork+0x1f/0x30\n\n  [72747.569686] task:fsstress        state:D stack:    \n---truncated---"
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          "providerMetadata": {
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          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2021-46987",
        "datePublished": "2024-02-28T08:13:14.690Z",
        "dateReserved": "2024-02-27T18:42:55.947Z",
        "dateUpdated": "2026-05-23T15:18:53.690Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.