{
   "containers": {
      "cna": {
         "providerMetadata": {
            "orgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038"
         },
         "descriptions": [
            {
               "lang": "en",
               "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/bhi: Avoid warning in #DB handler due to BHI mitigation\n\nWhen BHI mitigation is enabled, if SYSENTER is invoked with the TF flag set\nthen entry_SYSENTER_compat() uses CLEAR_BRANCH_HISTORY and calls the\nclear_bhb_loop() before the TF flag is cleared. This causes the #DB handler\n(exc_debug_kernel()) to issue a warning because single-step is used outside the\nentry_SYSENTER_compat() function.\n\nTo address this issue, entry_SYSENTER_compat() should use CLEAR_BRANCH_HISTORY\nafter making sure the TF flag is cleared.\n\nThe problem can be reproduced with the following sequence:\n\n  $ cat sysenter_step.c\n  int main()\n  { asm(\"pushf; pop %ax; bts $8,%ax; push %ax; popf; sysenter\"); }\n\n  $ gcc -o sysenter_step sysenter_step.c\n\n  $ ./sysenter_step\n  Segmentation fault (core dumped)\n\nThe program is expected to crash, and the #DB handler will issue a warning.\n\nKernel log:\n\n  WARNING: CPU: 27 PID: 7000 at arch/x86/kernel/traps.c:1009 exc_debug_kernel+0xd2/0x160\n  ...\n  RIP: 0010:exc_debug_kernel+0xd2/0x160\n  ...\n  Call Trace:\n  <#DB>\n   ? show_regs+0x68/0x80\n   ? __warn+0x8c/0x140\n   ? exc_debug_kernel+0xd2/0x160\n   ? report_bug+0x175/0x1a0\n   ? handle_bug+0x44/0x90\n   ? exc_invalid_op+0x1c/0x70\n   ? asm_exc_invalid_op+0x1f/0x30\n   ? exc_debug_kernel+0xd2/0x160\n   exc_debug+0x43/0x50\n   asm_exc_debug+0x1e/0x40\n  RIP: 0010:clear_bhb_loop+0x0/0xb0\n  ...\n  </#DB>\n  <TASK>\n   ? entry_SYSENTER_compat_after_hwframe+0x6e/0x8d\n  </TASK>\n\n  [ bp: Massage commit message. ]"
            }
         ],
         "affected": [
            {
               "product": "Linux",
               "vendor": "Linux",
               "defaultStatus": "unaffected",
               "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
               "programFiles": [
                  "arch/x86/entry/entry_64_compat.S"
               ],
               "versions": [
                  {
                     "version": "bd53ec80f218",
                     "lessThan": "db56615e96c4",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "07dbb10f153f",
                     "lessThan": "a765679defe1",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "eb36b0dce213",
                     "lessThan": "dae3543db8f0",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "7390db8aea0d",
                     "lessThan": "08518d48e5b7",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "7390db8aea0d",
                     "lessThan": "ac8b270b61d4",
                     "status": "affected",
                     "versionType": "git"
                  }
               ]
            },
            {
               "product": "Linux",
               "vendor": "Linux",
               "defaultStatus": "affected",
               "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
               "programFiles": [
                  "arch/x86/entry/entry_64_compat.S"
               ],
               "versions": [
                  {
                     "version": "6.9",
                     "status": "affected"
                  },
                  {
                     "version": "0",
                     "lessThan": "6.9",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "5.15.163",
                     "lessThanOrEqual": "5.15.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "6.1.100",
                     "lessThanOrEqual": "6.1.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "6.6.41",
                     "lessThanOrEqual": "6.6.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "6.9.10",
                     "lessThanOrEqual": "6.9.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "6.10",
                     "lessThanOrEqual": "*",
                     "status": "unaffected",
                     "versionType": "original_commit_for_fix"
                  }
               ]
            }
         ],
         "references": [
            {
               "url": "https://git.kernel.org/stable/c/db56615e96c439e13783d7715330e824b4fd4b84"
            },
            {
               "url": "https://git.kernel.org/stable/c/a765679defe1dc1b8fa01928a6ad6361e72a1364"
            },
            {
               "url": "https://git.kernel.org/stable/c/dae3543db8f0cf8ac1a198c3bb4b6e3c24d576cf"
            },
            {
               "url": "https://git.kernel.org/stable/c/08518d48e5b744620524f0acd7c26c19bda7f513"
            },
            {
               "url": "https://git.kernel.org/stable/c/ac8b270b61d48fcc61f052097777e3b5e11591e0"
            }
         ],
         "title": "x86/bhi: Avoid warning in #DB handler due to BHI mitigation",
         "x_generator": {
            "engine": "bippy-c9c4e1df01b2"
         }
      }
   },
   "cveMetadata": {
      "assignerOrgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038",
      "cveID": "CVE-2024-42240",
      "requesterUserId": "gregkh@kernel.org",
      "serial": "1",
      "state": "PUBLISHED"
   },
   "dataType": "CVE_RECORD",
   "dataVersion": "5.0"
}