CVE-2026-31444 (GCVE-0-2026-31444)

Vulnerability from cvelistv5 – Published: 2026-04-22 13:53 – Updated: 2026-04-22 13:53
VLAI?
Title
ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free and NULL deref in smb_grant_oplock() smb_grant_oplock() has two issues in the oplock publication sequence: 1) opinfo is linked into ci->m_op_list (via opinfo_add) before add_lease_global_list() is called. If add_lease_global_list() fails (kmalloc returns NULL), the error path frees the opinfo via __free_opinfo() while it is still linked in ci->m_op_list. Concurrent m_op_list readers (opinfo_get_list, or direct iteration in smb_break_all_levII_oplock) dereference the freed node. 2) opinfo->o_fp is assigned after add_lease_global_list() publishes the opinfo on the global lease list. A concurrent find_same_lease_key() can walk the lease list and dereference opinfo->o_fp->f_ci while o_fp is still NULL. Fix by restructuring the publication sequence to eliminate post-publish failure: - Set opinfo->o_fp before any list publication (fixes NULL deref). - Preallocate lease_table via alloc_lease_table() before opinfo_add() so add_lease_global_list() becomes infallible after publication. - Keep the original m_op_list publication order (opinfo_add before lease list) so concurrent opens via same_client_has_lease() and opinfo_get_list() still see the in-flight grant. - Use opinfo_put() instead of __free_opinfo() on err_out so that the RCU-deferred free path is used. This also requires splitting add_lease_global_list() to take a preallocated lease_table and changing its return type from int to void, since it can no longer fail.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 302fef75512b2c8329a3f5efab1ae7ba2562387a , < 9e785f004cbc56390479b77375726ea9b0d1a8a6 (git)
Affected: 08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c , < 7de55bba69cbf0f9280daaea385daf08bc076121 (git)
Affected: 1d6abf145615dbfe267ce3b0a271f95e3780e18e , < a5c6f6d6ceefed2d5210ee420fb75f8362461f46 (git)
Affected: ce8507ee82c888126d8e7565e27c016308d24cde , < 6d7e5a918c1d0aad06db0e17677b66fc9a471021 (git)
Affected: 1dfd062caa165ec9d7ee0823087930f3ab8a6294 , < 48623ec358c1c600fa1e38368746f933e0f1a617 (git)
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    Linux Linux Affected: 6.6.130 , < 6.6.131 (semver)
Affected: 6.12.78 , < 6.12.80 (semver)
Affected: 6.18.19 , < 6.18.21 (semver)
Affected: 6.19.9 , < 6.19.11 (semver)
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{
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free and NULL deref in smb_grant_oplock()\n\nsmb_grant_oplock() has two issues in the oplock publication sequence:\n\n1) opinfo is linked into ci-\u003em_op_list (via opinfo_add) before\n   add_lease_global_list() is called.  If add_lease_global_list()\n   fails (kmalloc returns NULL), the error path frees the opinfo\n   via __free_opinfo() while it is still linked in ci-\u003em_op_list.\n   Concurrent m_op_list readers (opinfo_get_list, or direct iteration\n   in smb_break_all_levII_oplock) dereference the freed node.\n\n2) opinfo-\u003eo_fp is assigned after add_lease_global_list() publishes\n   the opinfo on the global lease list.  A concurrent\n   find_same_lease_key() can walk the lease list and dereference\n   opinfo-\u003eo_fp-\u003ef_ci while o_fp is still NULL.\n\nFix by restructuring the publication sequence to eliminate post-publish\nfailure:\n\n- Set opinfo-\u003eo_fp before any list publication (fixes NULL deref).\n- Preallocate lease_table via alloc_lease_table() before opinfo_add()\n  so add_lease_global_list() becomes infallible after publication.\n- Keep the original m_op_list publication order (opinfo_add before\n  lease list) so concurrent opens via same_client_has_lease() and\n  opinfo_get_list() still see the in-flight grant.\n- Use opinfo_put() instead of __free_opinfo() on err_out so that\n  the RCU-deferred free path is used.\n\nThis also requires splitting add_lease_global_list() to take a\npreallocated lease_table and changing its return type from int to void,\nsince it can no longer fail."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-04-22T13:53:41.351Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/9e785f004cbc56390479b77375726ea9b0d1a8a6"
        },
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          "url": "https://git.kernel.org/stable/c/7de55bba69cbf0f9280daaea385daf08bc076121"
        },
        {
          "url": "https://git.kernel.org/stable/c/a5c6f6d6ceefed2d5210ee420fb75f8362461f46"
        },
        {
          "url": "https://git.kernel.org/stable/c/6d7e5a918c1d0aad06db0e17677b66fc9a471021"
        },
        {
          "url": "https://git.kernel.org/stable/c/48623ec358c1c600fa1e38368746f933e0f1a617"
        }
      ],
      "title": "ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()",
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    "cveId": "CVE-2026-31444",
    "datePublished": "2026-04-22T13:53:41.351Z",
    "dateReserved": "2026-03-09T15:48:24.090Z",
    "dateUpdated": "2026-04-22T13:53:41.351Z",
    "state": "PUBLISHED"
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      "date": "2026-04-23",
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  }
}


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