net: skbuff: fix missing zerocopy reference in pskb_carve helpers_CVE-2026-52943

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: skbuff: fix missing zerocopy reference in pskb_carve helpers\n\npskb_carve_inside_header() and pskb_carve_inside_nonlinear() both copy\nthe old skb_shared_info header into a new buffer via memcpy(), which\nincludes the destructor_arg pointer (uarg) for MSG_ZEROCOPY skbs.\nNeither function calls net_zcopy_get() for the new shinfo, creating an\nunaccounted holder: every skb_shared_info with destructor_arg set will\ncall skb_zcopy_clear() once when freed, but the corresponding\nnet_zcopy_get() was never called for the new copy. Repeated calls\ndrive uarg->refcnt to zero prematurely, freeing ubuf_info_msgzc while\nTX skbs still hold live destructor_arg pointers.\n\nKASAN reports use-after-free on a freed ubuf_info_msgzc:\n\n  BUG: KASAN: slab-use-after-free in skb_release_data+0x77b/0x810\n  Read of size 8 at addr ffff88801574d3e8 by task poc/220\n\n  Call Trace:\n   skb_release_data+0x77b/0x810\n   kfree_skb_list_reason+0x13e/0x610\n   skb_release_data+0x4cd/0x810\n   sk_skb_reason_drop+0xf3/0x340\n   skb_queue_purge_reason+0x282/0x440\n   rds_tcp_inc_free+0x1e/0x30\n   rds_recvmsg+0x354/0x1780\n   __sys_recvmsg+0xdf/0x180\n\n  Allocated by task 219:\n   msg_zerocopy_realloc+0x157/0x7b0\n   tcp_sendmsg_locked+0x2892/0x3ba0\n\n  Freed by task 219:\n   ip_recv_error+0x74a/0xb10\n   tcp_recvmsg+0x475/0x530\n\nThe skb consuming the late access still referenced the same uarg via\nshinfo->destructor_arg copied by pskb_carve_inside_nonlinear() without\na refcount bump. This has been verified to be reliably exploitable: a\nworking proof-of-concept achieves full root privilege escalation from\nan unprivileged local user on a default kernel configuration.\n\nThe fix follows the pattern of pskb_expand_head() which has the same\nmemcpy/cloned structure. For pskb_carve_inside_header(), net_zcopy_get()\nis placed after skb_orphan_frags() succeeds, so the orphan error path\nneeds no cleanup. For pskb_carve_inside_nonlinear(), net_zcopy_get() is\nplaced after all failure points and just before skb_release_data(), so\nno error path needs cleanup at all -- matching pskb_expand_head() more\nclosely and avoiding the need for a balancing net_zcopy_put().",
    "published": "2026-06-24T09:00:12.292Z",
    "modified": "2026-06-28T06:37:01.760Z",
    "type": "cve",
    "title": "net: skbuff: fix missing zerocopy reference in pskb_carve helpers",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/8dbed691e43a50903658130bde0fcb5abc425b37\nhttps://git.kernel.org/stable/c/9b40bdc2a3298225dffab8158208a0d8c6300578\nhttps://git.kernel.org/stable/c/fd470f0a97b8e9a125f520265d2f3b088ffb5b8a\nhttps://git.kernel.org/stable/c/ceafb893b12f23331dcc5ff9587e643c3a40ee9f\nhttps://git.kernel.org/stable/c/2e0e74c59b2761a414d9f48d7bee1e45220b2427\nhttps://git.kernel.org/stable/c/96a4713ae041cc85e712bac682cd2e644004d6c6\nhttps://git.kernel.org/stable/c/474d6c771d798bca84f0a140b611e36743511e18\nhttps://git.kernel.org/stable/c/98d0912e9f841e5529a5b89a972805f34cb1c69d",
    "id": "CVE-2026-52943",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 6fa01ccd883021105e9f8af7d04b9f156fa3494a\nLinux Linux 4.7",
    "sourceHref": "",
    "cvss": {
        "score": 7.8,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
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        "baseScore": 0,
        "baseSeverity": "",
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        "attackComplexity": "",
        "privilegesRequired": "",
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        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
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            "baseScore": 0,
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "6fa01ccd883021105e9f8af7d04b9f156fa3494a",
    "vendor": "Linux",
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    "ai_score": 0
}