CVE-2026-31715 (GCVE-0-2026-31715)
Vulnerability from cvelistv5
Published
2026-05-01 13:56
Modified
2026-05-17 15:21
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix UAF caused by decrementing sbi->nr_pages[] in f2fs_write_end_io() The xfstests case "generic/107" and syzbot have both reported a NULL pointer dereference. The concurrent scenario that triggers the panic is as follows: F2FS_WB_CP_DATA write callback umount - f2fs_write_checkpoint - f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA) - blk_mq_end_request - bio_endio - f2fs_write_end_io : dec_page_count(sbi, F2FS_WB_CP_DATA) : wake_up(&sbi->cp_wait) - kill_f2fs_super - kill_block_super - f2fs_put_super : iput(sbi->node_inode) : sbi->node_inode = NULL : f2fs_in_warm_node_list - is_node_folio // sbi->node_inode is NULL and panic The root cause is that f2fs_put_super() calls iput(sbi->node_inode) and sets sbi->node_inode to NULL after sbi->nr_pages[F2FS_WB_CP_DATA] is decremented to zero. As a result, f2fs_in_warm_node_list() may dereference a NULL node_inode when checking whether a folio belongs to the node inode, leading to a panic. This patch fixes the issue by calling f2fs_in_warm_node_list() before decrementing sbi->nr_pages[F2FS_WB_CP_DATA], thus preventing the use-after-free condition.
References
Impacted products
Vendor Product Version
Linux Linux Version: 50fa53eccf9f911a5b435248a2b0bd484fd82e5e
Version: 50fa53eccf9f911a5b435248a2b0bd484fd82e5e
Version: 50fa53eccf9f911a5b435248a2b0bd484fd82e5e
Version: 50fa53eccf9f911a5b435248a2b0bd484fd82e5e
Version: 50fa53eccf9f911a5b435248a2b0bd484fd82e5e
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{
  "containers": {
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/f2fs/data.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "versionType": "semver"
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1-rc1",
              "versionType": "original_commit_for_fix"
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix UAF caused by decrementing sbi-\u003enr_pages[] in f2fs_write_end_io()\n\nThe xfstests case \"generic/107\" and syzbot have both reported a NULL\npointer dereference.\n\nThe concurrent scenario that triggers the panic is as follows:\n\nF2FS_WB_CP_DATA write callback          umount\n                                        - f2fs_write_checkpoint\n                                         - f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA)\n- blk_mq_end_request\n - bio_endio\n  - f2fs_write_end_io\n   : dec_page_count(sbi, F2FS_WB_CP_DATA)\n   : wake_up(\u0026sbi-\u003ecp_wait)\n                                        - kill_f2fs_super\n                                         - kill_block_super\n                                          - f2fs_put_super\n                                           : iput(sbi-\u003enode_inode)\n                                           : sbi-\u003enode_inode = NULL\n   : f2fs_in_warm_node_list\n    - is_node_folio // sbi-\u003enode_inode is NULL and panic\n\nThe root cause is that f2fs_put_super() calls iput(sbi-\u003enode_inode) and\nsets sbi-\u003enode_inode to NULL after sbi-\u003enr_pages[F2FS_WB_CP_DATA] is\ndecremented to zero. As a result, f2fs_in_warm_node_list() may\ndereference a NULL node_inode when checking whether a folio belongs to\nthe node inode, leading to a panic.\n\nThis patch fixes the issue by calling f2fs_in_warm_node_list() before\ndecrementing sbi-\u003enr_pages[F2FS_WB_CP_DATA], thus preventing the\nuse-after-free condition."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-17T15:21:34.548Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1171f329cf1c175321251ac40fd126150d7ad1e8"
        },
        {
          "url": "https://git.kernel.org/stable/c/7be222de96c0f9eee6e65eeb017ef855ee185cfa"
        },
        {
          "url": "https://git.kernel.org/stable/c/963d2e24d9d92a31e6773b0f642214f10013ebf7"
        },
        {
          "url": "https://git.kernel.org/stable/c/188bb65f247a7a7c62f287c9a263aee3cad96fa5"
        },
        {
          "url": "https://git.kernel.org/stable/c/2d9c4a4ed4eef1f82c5b16b037aee8bad819fd53"
        }
      ],
      "title": "f2fs: fix UAF caused by decrementing sbi-\u003enr_pages[] in f2fs_write_end_io()",
      "x_generator": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31715",
    "datePublished": "2026-05-01T13:56:10.591Z",
    "dateReserved": "2026-03-09T15:48:24.133Z",
    "dateUpdated": "2026-05-17T15:21:34.548Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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