9p/xen: protect xen_9pfs_front_free against concurrent calls_CVE-2026-43249

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p/xen: protect xen_9pfs_front_free against concurrent calls\n\nThe xenwatch thread can race with other back-end change notifications\nand call xen_9pfs_front_free() twice, hitting the observed general\nprotection fault due to a double-free. Guard the teardown path so only\none caller can release the front-end state at a time, preventing the\ncrash.\n\nThis is a fix for the following double-free:\n\n[   27.052347] Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI\n[   27.052357] CPU: 0 UID: 0 PID: 32 Comm: xenwatch Not tainted 6.18.0-02087-g51ab33fc0a8b-dirty #60 PREEMPT(none)\n[   27.052363] RIP: e030:xen_9pfs_front_free+0x1d/0x150\n[   27.052368] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 41 55 41 54 55 48 89 fd 48 c7 c7 48 d0 92 85 53 e8 cb cb 05 00 48 8b 45 08 48 8b 55 00 <48> 3b 28 0f 85 f9 28 35 fe 48 3b 6a 08 0f 85 ef 28 35 fe 48 89 42\n[   27.052377] RSP: e02b:ffffc9004016fdd0 EFLAGS: 00010246\n[   27.052381] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88800d66e400 RCX: 0000000000000000\n[   27.052385] RDX: 6b6b6b6b6b6b6b6b RSI: 0000000000000000 RDI: 0000000000000000\n[   27.052389] RBP: ffff88800a887040 R08: 0000000000000000 R09: 0000000000000000\n[   27.052393] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888009e46b68\n[   27.052397] R13: 0000000000000200 R14: 0000000000000000 R15: ffff88800a887040\n[   27.052404] FS:  0000000000000000(0000) GS:ffff88808ca57000(0000) knlGS:0000000000000000\n[   27.052408] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   27.052412] CR2: 00007f9714004360 CR3: 0000000004834000 CR4: 0000000000050660\n[   27.052418] Call Trace:\n[   27.052420]  <TASK>\n[   27.052422]  xen_9pfs_front_changed+0x5d5/0x720\n[   27.052426]  ? xenbus_otherend_changed+0x72/0x140\n[   27.052430]  ? __pfx_xenwatch_thread+0x10/0x10\n[   27.052434]  xenwatch_thread+0x94/0x1c0\n[   27.052438]  ? __pfx_autoremove_wake_function+0x10/0x10\n[   27.052442]  kthread+0xf8/0x240\n[   27.052445]  ? __pfx_kthread+0x10/0x10\n[   27.052449]  ? __pfx_kthread+0x10/0x10\n[   27.052452]  ret_from_fork+0x16b/0x1a0\n[   27.052456]  ? __pfx_kthread+0x10/0x10\n[   27.052459]  ret_from_fork_asm+0x1a/0x30\n[   27.052463]  </TASK>\n[   27.052465] Modules linked in:\n[   27.052471] ---[ end trace 0000000000000000 ]---",
    "published": "2026-05-06T11:28:40.290Z",
    "modified": "2026-05-08T12:41:35.086Z",
    "type": "cve",
    "title": "9p/xen: protect xen_9pfs_front_free against concurrent calls",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/a5d00dff97118a32fcf5fec7a4c3f864c4620c4e\nhttps://git.kernel.org/stable/c/59e7707492576bdbfa8c1dbe7d90791df31e4773\nhttps://git.kernel.org/stable/c/bf841d43f7a33d75675ba7f4e214ac1c67913065\nhttps://git.kernel.org/stable/c/ce8ded2e61f47747e31eeefb44dc24a2160a7e32",
    "id": "CVE-2026-43249",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux c15fe55d14b3b4ded5af2a3260877460a6ffb8ad\nLinux Linux c15fe55d14b3b4ded5af2a3260877460a6ffb8ad\nLinux Linux c15fe55d14b3b4ded5af2a3260877460a6ffb8ad\nLinux Linux c15fe55d14b3b4ded5af2a3260877460a6ffb8ad\nLinux Linux be03c4fe72384366fd4077a70966bd3b8fc49013\nLinux Linux 1ab4de11232e83b875b071aa44d1155634ca8a1e\nLinux Linux 7cc9dbae8a5f73bd555130384ea256018d28f283\nLinux Linux 3e0359f151ac151abe3fa71040e450ed69cb824b\nLinux Linux 8d3fc907d060c4fb33203e616a395a22083b6566\nLinux Linux 4f0e9244770f5b75a16d8c0929063cd336926764\nLinux Linux 5f6a8974e9ef317fe63f88bab1f33070195dd147\nLinux Linux 6.3",
    "sourceHref": "",
    "cvss": {
        "score": 8.8,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
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        "baseScore": 0,
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        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
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            "baseScore": 0,
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "c15fe55d14b3b4ded5af2a3260877460a6ffb8ad",
    "vendor": "Linux",
    "ai_description": "AI processing failed - no valid JSON found",
    "ai_severity": "",
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    "ai_score": 0
}