ghsa-643h-952w-33f5
Vulnerability from github
Published
2024-10-29 03:31
Modified
2024-11-08 18:30
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Details

In the Linux kernel, the following vulnerability has been resolved:

x86/bugs: Use code segment selector for VERW operand

Robert Gill reported below #GP in 32-bit mode when dosemu software was executing vm86() system call:

general protection fault: 0000 [#1] PREEMPT SMP CPU: 4 PID: 4610 Comm: dosemu.bin Not tainted 6.6.21-gentoo-x86 #1 Hardware name: Dell Inc. PowerEdge 1950/0H723K, BIOS 2.7.0 10/30/2010 EIP: restore_all_switch_stack+0xbe/0xcf EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000 ESI: 00000000 EDI: 00000000 EBP: 00000000 ESP: ff8affdc DS: 0000 ES: 0000 FS: 0000 GS: 0033 SS: 0068 EFLAGS: 00010046 CR0: 80050033 CR2: 00c2101c CR3: 04b6d000 CR4: 000406d0 Call Trace: show_regs+0x70/0x78 die_addr+0x29/0x70 exc_general_protection+0x13c/0x348 exc_bounds+0x98/0x98 handle_exception+0x14d/0x14d exc_bounds+0x98/0x98 restore_all_switch_stack+0xbe/0xcf exc_bounds+0x98/0x98 restore_all_switch_stack+0xbe/0xcf

This only happens in 32-bit mode when VERW based mitigations like MDS/RFDS are enabled. This is because segment registers with an arbitrary user value can result in #GP when executing VERW. Intel SDM vol. 2C documents the following behavior for VERW instruction:

#GP(0) - If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.

CLEAR_CPU_BUFFERS macro executes VERW instruction before returning to user space. Use %cs selector to reference VERW operand. This ensures VERW will not #GP for an arbitrary user %ds.

[ mingo: Fixed the SOB chain. ]

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{
  "affected": [],
  "aliases": [
    "CVE-2024-50072"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-10-29T01:15:04Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/bugs: Use code segment selector for VERW operand\n\nRobert Gill reported below #GP in 32-bit mode when dosemu software was\nexecuting vm86() system call:\n\n  general protection fault: 0000 [#1] PREEMPT SMP\n  CPU: 4 PID: 4610 Comm: dosemu.bin Not tainted 6.6.21-gentoo-x86 #1\n  Hardware name: Dell Inc. PowerEdge 1950/0H723K, BIOS 2.7.0 10/30/2010\n  EIP: restore_all_switch_stack+0xbe/0xcf\n  EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000\n  ESI: 00000000 EDI: 00000000 EBP: 00000000 ESP: ff8affdc\n  DS: 0000 ES: 0000 FS: 0000 GS: 0033 SS: 0068 EFLAGS: 00010046\n  CR0: 80050033 CR2: 00c2101c CR3: 04b6d000 CR4: 000406d0\n  Call Trace:\n   show_regs+0x70/0x78\n   die_addr+0x29/0x70\n   exc_general_protection+0x13c/0x348\n   exc_bounds+0x98/0x98\n   handle_exception+0x14d/0x14d\n   exc_bounds+0x98/0x98\n   restore_all_switch_stack+0xbe/0xcf\n   exc_bounds+0x98/0x98\n   restore_all_switch_stack+0xbe/0xcf\n\nThis only happens in 32-bit mode when VERW based mitigations like MDS/RFDS\nare enabled. This is because segment registers with an arbitrary user value\ncan result in #GP when executing VERW. Intel SDM vol. 2C documents the\nfollowing behavior for VERW instruction:\n\n  #GP(0) - If a memory operand effective address is outside the CS, DS, ES,\n\t   FS, or GS segment limit.\n\nCLEAR_CPU_BUFFERS macro executes VERW instruction before returning to user\nspace. Use %cs selector to reference VERW operand. This ensures VERW will\nnot #GP for an arbitrary user %ds.\n\n[ mingo: Fixed the SOB chain. ]",
  "id": "GHSA-643h-952w-33f5",
  "modified": "2024-11-08T18:30:47Z",
  "published": "2024-10-29T03:31:06Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-50072"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/38c5fe74f3bef98f75d16effa49836d50c9b6097"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/481b477ab63c7245715a3e57ba79eb87c2dc0d02"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ada431c6c31a2c8c37991c46089af5caa23a9c6e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bc576fbaf82deded606e69a00efe9752136bf91d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bfd1d223d80cb29a210caa1bd5e21f0816d58f02"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e4d2102018542e3ae5e297bc6e229303abff8a0f"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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