CVE-2026-93810 (GCVE-0-2026-93810)

Vulnerability from cvelistv5 – Published: 2026-09-24 16:02 – Updated: 2026-09-25 12:43
VLAI
Title
cachefiles: Fix double fput
Summary
In the Linux kernel, the following vulnerability has been resolved: cachefiles: Fix double fput Fix a double fput() in error handling in cachefiles_create_tmpfile().
Severity
7 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 24a81759b65fa85767739999d91523691c5e2ea5 , < e9c2e68c3890a935abbd5f54dbce653f9a16836c (git)
Affected: 24a81759b65fa85767739999d91523691c5e2ea5 , < 90b306eee037d0a6a8f4aac834b46e05c5ddd0bf (git)
Affected: 24a81759b65fa85767739999d91523691c5e2ea5 , < af6830cc12dfe86c832dccc9c9878a93aaa22f83 (git)
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Linux Linux Affected: 6.1
Unaffected: 0 , < 6.1 (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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          "programFiles": [
            "fs/cachefiles/namei.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: Fix double fput\n\nFix a double fput() in error handling in cachefiles_create_tmpfile()."
        }
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      "metrics": [
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            "baseSeverity": "HIGH",
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            "version": "3.1"
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          "scenarios": [
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              "lang": "en",
              "value": "AV:L - The extra fput is in cachefiles_create_tmpfile(), reached from nfs_fscache_open_file() (or CIFS/9p/AFS/Ceph fscache_use_cookie()) \u2192 fscache_perform_lookup() \u2192 cachefiles_lookup_cookie() \u2192 cachefiles_look_up_object() \u2192 cachefiles_create_file(), or from cachefiles_invalidate_cookie(); a local open/inval of an fscache-backed file is the entry, not a remote protocol message.\nAC:H - The double fput runs only when kernel_tmpfile_open()\u0027s file has a NULL f_op-\u003eread_iter or f_op-\u003ewrite_iter. cachefiles_add_cache() requires tmpfile/xattr/sync_fs and s_blocksize\u003c=PAGE_SIZE but never checks those f_ops; the only in-tree tmpfile FS lacking write_iter is hugetlbfs, which add_cache rejects, so an attacker cannot make a bound ext4/xfs/btrfs/f2fs tmpfile take this branch.\nPR:L - nfs_fscache_open_file() and the sibling fscache_use_cookie() open paths have no capable() check, so an unprivileged user with read access on an already-bound cachefiles/fscache mount drives cookie lookup into cachefiles_create_tmpfile(); cachefiles_daemon_open() needs init-namespace CAP_SYS_ADMIN, but that is not this trigger.\nUI:N - The attacker themselves open or invalidate files on the fscache-enabled netfs mount, which queues fscache_perform_lookup() into cachefiles_create_tmpfile(); no other user must mount the volume or issue cachefilesd commands.\nS:U - Double-putting the cache tmpfile\u0027s struct file corrupts host kernel file-refcount and filp_cachep state only; it does not cross a KVM/Xen, IOMMU, or other distinct authority.\nC:H - On the !read_iter/!write_iter branch, cachefiles_create_tmpfile() fput()s then err_unuse calls file_inode(file) and fput()s again. fscache_perform_lookup() runs in a PF_KTHREAD worker so the first put is deferred via delayed_fput_work; a later file_inode() on that pointer is a UAF read of a SLAB_TYPESAFE_BY_RCU struct file.\nI:H - The leftover fput before goto err_unuse is a struct-file double-put: if delayed __fput() has already file_free()\u0027d the tmpfile, the second file_ref_put() writes a recycled filp_cachep object (or an underflowed live ref into the dead zone), a UAF write primitive against struct file.\nA:H - The second put hits __file_ref_put_badval()\u0027s \"imbalanced put on file reference count\" WARN_ONCE, and if delayed_fput already ran, file_inode()/inode_lock/fput in cachefiles_create_tmpfile() err_unuse dereference freed memory and oops the fscache worker."
            }
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    "datePublished": "2026-09-24T16:02:46.426Z",
    "dateReserved": "2026-09-18T17:59:28.790Z",
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        "lastModified": "2026-09-25T13:17:21.853",
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}



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