{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  ext4: drain in-flight DIO before buffered write fallback  generic/746 started failing intermittently on ext3 (no-extent inodes). The test triggers 'Page cache invalidation failure on direct I/O' warnings and subsequent fsync returns -EIO. Adding a 50ms delay between ext4_buffered_write_iter() and filemap_write_and_wait_range() in ext4_dio_write_iter() makes the race almost always reproducible.  On no-extent inodes, DIO writes to holes cannot use unwritten extents, so ext4_iomap_alloc() leaves m_flags=0 and ext4_map_blocks() returns 0. The iomap layer then returns -ENOTBLK, causing fallback to buffered I/O.  The fallback path in ext4_dio_write_iter() calls ext4_buffered_write_iter() which dirties pages, then does flush and invalidate. However, there's an unprotected window between ext4_buffered_write_iter() returning (with inode lock released) and the subsequent flush+invalidate.  Concurrent async DIO completions from other threads can run kiocb_invalidate_post_direct_write() during this window. If pages have been re-dirtied, post-invalidation finds dirty pages and triggers the warning, setting -EIO in the error sequence.  Consider a file with two 4k extents: [hole][written]. Thread A does DIO to the written extent, while thread B does DIO spanning both:    kworker A (4k DIO, allocated block)    kworker B (8k DIO, fallback)   -----------------------------------    ----------------------------   inode_lock_shared()                    inode_lock_shared()   iomap_dio_rw():                        iomap_dio_rw():     kiocb_invalidate_pages -\u003e clean        iomap_begin -\u003e -ENOTBLK     submit_bio (async)                     dio-\u003esize = 0   inode_unlock_shared()                  inode_unlock_shared()    [bio pending in block layer]           /* fallback: lock released */                                          ext4_buffered_write_iter()                                            inode_lock(exclusive)                                            generic_perform_write()                                              -\u003e dirty pages [0, 8k]                                            inode_unlock(exclusive)                                           /* pages dirty, no lock */   [bio completes]                        filemap_write_and_wait_range()   iomap_dio_complete()                     -\u003e flush dirty pages     kiocb_invalidate_post_direct_write() invalidate_mapping_pages()       invalidate_inode_pages2_range()       -\u003e finds dirty page!       -\u003e dio_warn_stale_pagecache()       -\u003e errseq_set(-EIO)  This issue can be triggered through normal I/O paths, not just intentionally overlapping DIO writes from userspace. For example, generic/746 uses a loop device where multiple kworkers issue concurrent I/O to the backing file. Additionally, when block_size \u003c folio_size, non-overlapping DIO writes that share a large folio can also trigger the race.  Add inode_dio_wait() in ext4_buffered_write_iter() before ext4_write_checks() to drain all in-flight DIO. This ensures that all DIO clears existing pages before submitting IO (via kiocb_invalidate_pages()), all BIO waits for all DIO to complete (via inode_dio_wait()), and ext4_write_checks() observes the inode size after all completed DIO so that ext4_block_zero_eof() does not race with in-flight DIO, thus eliminating the race.",
  "id": "DEBIAN-CVE-2026-92501",
  "modified": "2026-09-18T04:47:37.514396156Z",
  "published": "2026-09-17T17:17:52.517Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-92501"
    }
  ],
  "upstream": [
    "CVE-2026-92501"
  ]
}