CVE-2025-71074 (GCVE-0-2025-71074)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:31 – Updated: 2026-02-09 08:34
VLAI?
Title
functionfs: fix the open/removal races
Summary
In the Linux kernel, the following vulnerability has been resolved: functionfs: fix the open/removal races ffs_epfile_open() can race with removal, ending up with file->private_data pointing to freed object. There is a total count of opened files on functionfs (both ep0 and dynamic ones) and when it hits zero, dynamic files get removed. Unfortunately, that removal can happen while another thread is in ffs_epfile_open(), but has not incremented the count yet. In that case open will succeed, leaving us with UAF on any subsequent read() or write(). The root cause is that ffs->opened is misused; atomic_dec_and_test() vs. atomic_add_return() is not a good idea, when object remains visible all along. To untangle that * serialize openers on ffs->mutex (both for ep0 and for dynamic files) * have dynamic ones use atomic_inc_not_zero() and fail if we had zero ->opened; in that case the file we are opening is doomed. * have the inodes of dynamic files marked on removal (from the callback of simple_recursive_removal()) - clear ->i_private there. * have open of dynamic ones verify they hadn't been already removed, along with checking that state is FFS_ACTIVE.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: ddf8abd2599491cbad959c700b90ba72a5dce8d0 , < e5bf5ee266633cb18fff6f98f0b7d59a62819eee (git)
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    Linux Linux Affected: 2.6.35
Unaffected: 0 , < 2.6.35 (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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          "programFiles": [
            "drivers/usb/gadget/function/f_fs.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfunctionfs: fix the open/removal races\n\nffs_epfile_open() can race with removal, ending up with file-\u003eprivate_data\npointing to freed object.\n\nThere is a total count of opened files on functionfs (both ep0 and\ndynamic ones) and when it hits zero, dynamic files get removed.\nUnfortunately, that removal can happen while another thread is\nin ffs_epfile_open(), but has not incremented the count yet.\nIn that case open will succeed, leaving us with UAF on any subsequent\nread() or write().\n\nThe root cause is that ffs-\u003eopened is misused; atomic_dec_and_test() vs.\natomic_add_return() is not a good idea, when object remains visible all\nalong.\n\nTo untangle that\n\t* serialize openers on ffs-\u003emutex (both for ep0 and for dynamic files)\n\t* have dynamic ones use atomic_inc_not_zero() and fail if we had\nzero -\u003eopened; in that case the file we are opening is doomed.\n\t* have the inodes of dynamic files marked on removal (from the\ncallback of simple_recursive_removal()) - clear -\u003ei_private there.\n\t* have open of dynamic ones verify they hadn\u0027t been already removed,\nalong with checking that state is FFS_ACTIVE."
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      "providerMetadata": {
        "dateUpdated": "2026-02-09T08:34:25.029Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/e5bf5ee266633cb18fff6f98f0b7d59a62819eee"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-71074",
    "datePublished": "2026-01-13T15:31:27.413Z",
    "dateReserved": "2026-01-13T15:30:19.647Z",
    "dateUpdated": "2026-02-09T08:34:25.029Z",
    "state": "PUBLISHED"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2025-71074\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-01-13T16:16:06.860\",\"lastModified\":\"2026-01-23T11:15:48.830\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nfunctionfs: fix the open/removal races\\n\\nffs_epfile_open() can race with removal, ending up with file-\u003eprivate_data\\npointing to freed object.\\n\\nThere is a total count of opened files on functionfs (both ep0 and\\ndynamic ones) and when it hits zero, dynamic files get removed.\\nUnfortunately, that removal can happen while another thread is\\nin ffs_epfile_open(), but has not incremented the count yet.\\nIn that case open will succeed, leaving us with UAF on any subsequent\\nread() or write().\\n\\nThe root cause is that ffs-\u003eopened is misused; atomic_dec_and_test() vs.\\natomic_add_return() is not a good idea, when object remains visible all\\nalong.\\n\\nTo untangle that\\n\\t* serialize openers on ffs-\u003emutex (both for ep0 and for dynamic files)\\n\\t* have dynamic ones use atomic_inc_not_zero() and fail if we had\\nzero -\u003eopened; in that case the file we are opening is doomed.\\n\\t* have the inodes of dynamic files marked on removal (from the\\ncallback of simple_recursive_removal()) - clear -\u003ei_private there.\\n\\t* have open of dynamic ones verify they hadn\u0027t been already removed,\\nalong with checking that state is FFS_ACTIVE.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/e5bf5ee266633cb18fff6f98f0b7d59a62819eee\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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