{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2024-56549",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2024-56549"
  ],
  "published": "2024-12-27T14:12:25Z",
  "summary": "cachefiles: Fix NULL pointer dereference in object->file",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: Fix NULL pointer dereference in object->file\n\nAt present, the object->file has the NULL pointer dereference problem in\nondemand-mode. The root cause is that the allocated fd and object->file\nlifetime are inconsistent, and the user-space invocation to anon_fd uses\nobject->file. Following is the process that triggers the issue:\n\n\t  [write fd]\t\t\t\t[umount]\ncachefiles_ondemand_fd_write_iter\n\t\t\t\t       fscache_cookie_state_machine\n\t\t\t\t\t cachefiles_withdraw_cookie\n  if (!file) return -ENOBUFS\n\t\t\t\t\t   cachefiles_clean_up_object\n\t\t\t\t\t     cachefiles_unmark_inode_in_use\n\t\t\t\t\t     fput(object->file)\n\t\t\t\t\t     object->file = NULL\n  // file NULL pointer dereference!\n  __cachefiles_write(..., file, ...)\n\nFix this issue by add an additional reference count to the object->file\nbefore write/llseek, and decrement after it finished.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2024-56549"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d6bba3ece960129a553d4b16f1b00c884dc0993a"
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      "url": "https://git.kernel.org/stable/c/785408bbafcfa24c9fc5b251f03fd0780ce182bd"
    },
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      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f98770440c9bc468e2fd878212ec9526dbe08293"
    },
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      "url": "https://git.kernel.org/stable/c/9582c7664103c9043e80a78f5c382aa6bdd67418"
    },
    {
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    "upstream_modified": "2026-08-05T11:52:36Z",
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      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerable code is reached through local file-descriptor operations (write()/lseek() on a cachefiles on-demand anon fd) raced against local cookie withdrawal (umount, LRU discard, invalidation). There is no remote or adjacent-network path into fs/cachefiles/ondemand.c.\nAC:L - The attacker controls both sides of the race \u2014 they generate the demand-read traffic that makes the daemon write on the anon fd, and they trigger the withdrawal (umount of their erofs-on-fscache mount, or letting the cookie idle past the ~2s LRU timeout) \u2014 and can retry the sequence indefinitely until the window is hit.\nPR:L - Although /dev/cachefiles itself requires CAP_SYS_ADMIN, an unprivileged local user of an on-demand erofs/fscache mount (e.g. inside a container using an on-demand image) drives both the daemon's writes and the cookie withdrawal without ever needing the anon fd, so basic unprivileged local access suffices.\nUI:N - No victim action is needed; the cachefiles daemon services demand-read requests automatically as part of normal operation, and the withdrawal path is driven by the attacker's own filesystem activity.\nS:U - The corruption is confined to kernel memory within the same security authority; this is standard kernel memory corruption, not a hypervisor, IOMMU, or sandbox boundary crossing.\nC:H - The use-after-free on struct file lets llseek/SEEK_DATA/SEEK_HOLE and DIO operations act on a freed slot that filp_cachep (SLAB_TYPESAFE_BY_RCU) hands out as an unrelated struct file, exposing freed-memory contents and redirecting reads to files the attacker has no access to.\nI:H - __cachefiles_write() calls get_file() and vfs_iocb_iter_write() on the dangling pointer, inflating a reallocated file's refcount (setting up a further UAF) and writing attacker-influenced cache data \u2014 plus fallocate() \u2014 into an unrelated open file, giving a controlled write primitive.\nA:H - Dereferencing the freed/NULLed object->file causes a kernel oops or panic, and the refcount corruption on the reallocated struct file leads to further fatal memory corruption."
    }
  }
}