FKIE_CVE-2026-98745

Vulnerability from fkie_nvd - Published: 2026-10-18 16:17 - Updated: 2026-10-30 13:21
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: arm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems When system_supports_sme() is true but system_supports_sve() is false, restoring a specifically crafted SVE signal context can result in the task erroneously having non-streaming SVE state. Subsequent attempts to manipulate the task's FPSIMD/SVE/SME state can result in a variety of problems, including fatal EL1 UNDEFs. In such configurations, the kernel always creates an SVE signal context when delivering a signal, and this can only be in one of two states: (1) SVE_SIG_FLAG_SM is set, and an SVE payload is present containing streaming mode SVE state. The recorded VL is the task's live streaming VL. (2) SVE_SIG_FLAG_SM is clear, and an SVE payload is not present. The FPSIMD context contains the non-streaming mode FPSIMD state. The recorded VL is 0. Currently restore_sve_fpsimd_context() correctly rejects cases where SVE_SIG_FLAG_SM is set and an SVE payload is not present, but fails to reject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is present. Consequently, restore_sve_fpsimd_context() can place the task in a state where it has non-streaming SVE state even when this is not supported by HW. For example, this can cause a later EL1 UNDEF when the kernel attempts to restore the task's ZCR_EL1 value: | # ./sme-sigcontext-to-sve | Internal error: Oops - Undefined instruction: 0000000002000000 [#1] SMP | Modules linked in: | CPU: 0 UID: 0 PID: 131 Comm: sme-sigcontext- Not tainted 7.3.0-rc1 #1 PREEMPT | Hardware name: linux,dummy-virt (DT) | pstate: 61402009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) | pc : fpsimd_restore_current_state+0x258/0x458 | lr : exit_to_user_mode_loop+0xb8/0x188 | sp : ffff80008056be40 | x29: ffff80008056be40 x28: fff00000c1670000 x27: 0000000000000000 | x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 | x23: ffff80008056bec0 x22: 0000000000000008 x21: 0000000000000040 | x20: 0000000000000081 x19: 0000000008800010 x18: 0000000000000000 | x17: 0000fffffd412570 x16: 0000000000001000 x15: 0000fffffd4123b0 | x14: 0000fffffd412780 x13: 0000fffffd412be8 x12: 0000000047435300 | x11: 0000fffffd412570 x10: 0000000000000000 x9 : 0000000045585401 | x8 : fff00000c18a6c44 x7 : 0000000000000000 x6 : 0000000000000002 | x5 : 0000000000000002 x4 : ffff800080568000 x3 : 0000000000000001 | x2 : 0000000008800010 x1 : fff00000c1670000 x0 : 0000000008800000 | Call trace: | fpsimd_restore_current_state+0x258/0x458 (P) | exit_to_user_mode_loop+0xb8/0x188 | el0_svc+0x1cc/0x1d0 | el0t_64_sync_handler+0xa0/0xe4 | el0t_64_sync+0x198/0x19c | Code: d5384101 f9400020 53175c03 36b80de0 (d5381202) | ---[ end trace 0000000000000000 ]--- | Kernel panic - not syncing: Oops - Undefined instruction: Fatal exception in interrupt | Kernel Offset: 0x291fb1000000 from 0xffff800080000000 | PHYS_OFFSET: 0x40000000 | CPU features: 0x0,00000000,0052802f,ffb88f43,3afcf73f | Memory Limit: none Rework restore_sve_fpsimd_context() to reject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is not present. As parse_user_sigframe() rejects SVE signal frames when neither SVE nor SME are supported, it isn't necessary for restore_sve_fpsimd_context() to handle the case where neither are supported.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/052acee9880114879b5c221fc8dad69b786d0938
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2bce6f006cfe0b60e8249fd8d51396d99355cba3
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6c5b3ec340921617d965b7c87959560e886e778f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/88c1c611552b24658eb61244086691c02be2013b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e060d9069b49fe55f38057dfe592068014652671
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f2338929c7663859c0c74dd6fef2c0245066f845
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/arm64/kernel/signal.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6c5b3ec340921617d965b7c87959560e886e778f",
              "status": "affected",
              "version": "05458ee3ff82b31a4564836a84ef20d6c233dfc7",
              "versionType": "git"
            },
            {
              "lessThan": "052acee9880114879b5c221fc8dad69b786d0938",
              "status": "affected",
              "version": "7dde62f0687c8856b6c0660066c7ee83a6a6f033",
              "versionType": "git"
            },
            {
              "lessThan": "f2338929c7663859c0c74dd6fef2c0245066f845",
              "status": "affected",
              "version": "7dde62f0687c8856b6c0660066c7ee83a6a6f033",
              "versionType": "git"
            },
            {
              "lessThan": "2bce6f006cfe0b60e8249fd8d51396d99355cba3",
              "status": "affected",
              "version": "7dde62f0687c8856b6c0660066c7ee83a6a6f033",
              "versionType": "git"
            },
            {
              "lessThan": "88c1c611552b24658eb61244086691c02be2013b",
              "status": "affected",
              "version": "7dde62f0687c8856b6c0660066c7ee83a6a6f033",
              "versionType": "git"
            },
            {
              "lessThan": "e060d9069b49fe55f38057dfe592068014652671",
              "status": "affected",
              "version": "7dde62f0687c8856b6c0660066c7ee83a6a6f033",
              "versionType": "git"
            },
            {
              "lessThan": "6.1.191",
              "status": "affected",
              "version": "6.1.7",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/arm64/kernel/signal.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.2"
            },
            {
              "lessThan": "6.2",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.191",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.113",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.56",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\narm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems\n\nWhen system_supports_sme() is true but system_supports_sve() is false,\nrestoring a specifically crafted SVE signal context can result in the\ntask erroneously having non-streaming SVE state. Subsequent attempts to\nmanipulate the task\u0027s FPSIMD/SVE/SME state can result in a variety of\nproblems, including fatal EL1 UNDEFs.\n\nIn such configurations, the kernel always creates an SVE signal context\nwhen delivering a signal, and this can only be in one of two states:\n\n(1) SVE_SIG_FLAG_SM is set, and an SVE payload is present containing\n    streaming mode SVE state. The recorded VL is the task\u0027s live\n    streaming VL.\n\n(2) SVE_SIG_FLAG_SM is clear, and an SVE payload is not present. The\n    FPSIMD context contains the non-streaming mode FPSIMD state. The\n    recorded VL is 0.\n\nCurrently restore_sve_fpsimd_context() correctly rejects cases where\nSVE_SIG_FLAG_SM is set and an SVE payload is not present, but fails to\nreject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is\npresent. Consequently, restore_sve_fpsimd_context() can place the task\nin a state where it has non-streaming SVE state even when this is not\nsupported by HW.\n\nFor example, this can cause a later EL1 UNDEF when the kernel attempts to\nrestore the task\u0027s ZCR_EL1 value:\n\n| # ./sme-sigcontext-to-sve\n| Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP\n| Modules linked in:\n| CPU: 0 UID: 0 PID: 131 Comm: sme-sigcontext- Not tainted 7.3.0-rc1 #1 PREEMPT\n| Hardware name: linux,dummy-virt (DT)\n| pstate: 61402009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)\n| pc : fpsimd_restore_current_state+0x258/0x458\n| lr : exit_to_user_mode_loop+0xb8/0x188\n| sp : ffff80008056be40\n| x29: ffff80008056be40 x28: fff00000c1670000 x27: 0000000000000000\n| x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000\n| x23: ffff80008056bec0 x22: 0000000000000008 x21: 0000000000000040\n| x20: 0000000000000081 x19: 0000000008800010 x18: 0000000000000000\n| x17: 0000fffffd412570 x16: 0000000000001000 x15: 0000fffffd4123b0\n| x14: 0000fffffd412780 x13: 0000fffffd412be8 x12: 0000000047435300\n| x11: 0000fffffd412570 x10: 0000000000000000 x9 : 0000000045585401\n| x8 : fff00000c18a6c44 x7 : 0000000000000000 x6 : 0000000000000002\n| x5 : 0000000000000002 x4 : ffff800080568000 x3 : 0000000000000001\n| x2 : 0000000008800010 x1 : fff00000c1670000 x0 : 0000000008800000\n| Call trace:\n|  fpsimd_restore_current_state+0x258/0x458 (P)\n|  exit_to_user_mode_loop+0xb8/0x188\n|  el0_svc+0x1cc/0x1d0\n|  el0t_64_sync_handler+0xa0/0xe4\n|  el0t_64_sync+0x198/0x19c\n| Code: d5384101 f9400020 53175c03 36b80de0 (d5381202)\n| ---[ end trace 0000000000000000 ]---\n| Kernel panic - not syncing: Oops - Undefined instruction: Fatal exception in interrupt\n| Kernel Offset: 0x291fb1000000 from 0xffff800080000000\n| PHYS_OFFSET: 0x40000000\n| CPU features: 0x0,00000000,0052802f,ffb88f43,3afcf73f\n| Memory Limit: none\n\nRework restore_sve_fpsimd_context() to reject cases where\nSVE_SIG_FLAG_SM is clear and an SVE payload is not present. As\nparse_user_sigframe() rejects SVE signal frames when neither SVE nor SME\nare supported, it isn\u0027t necessary for restore_sve_fpsimd_context() to\nhandle the case where neither are supported."
    }
  ],
  "id": "CVE-2026-98745",
  "lastModified": "2026-10-30T13:21:23.220",
  "metrics": {},
  "published": "2026-10-18T16:17:28.237",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/052acee9880114879b5c221fc8dad69b786d0938"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2bce6f006cfe0b60e8249fd8d51396d99355cba3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6c5b3ec340921617d965b7c87959560e886e778f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/88c1c611552b24658eb61244086691c02be2013b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e060d9069b49fe55f38057dfe592068014652671"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f2338929c7663859c0c74dd6fef2c0245066f845"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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