ghsa-jgx8-h977-4wfh
Vulnerability from github
Published
2024-05-21 18:31
Modified
2024-05-21 18:31
Details

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

riscv: VMAP_STACK overflow detection thread-safe

commit 31da94c25aea ("riscv: add VMAP_STACK overflow detection") added support for CONFIG_VMAP_STACK. If overflow is detected, CPU switches to shadow_stack temporarily before switching finally to per-cpu overflow_stack.

If two CPUs/harts are racing and end up in over flowing kernel stack, one or both will end up corrupting each other state because shadow_stack is not per-cpu. This patch optimizes per-cpu overflow stack switch by directly picking per-cpu overflow_stack and gets rid of shadow_stack.

Following are the changes in this patch

  • Defines an asm macro to obtain per-cpu symbols in destination register.
  • In entry.S, when overflow is detected, per-cpu overflow stack is located using per-cpu asm macro. Computing per-cpu symbol requires a temporary register. x31 is saved away into CSR_SCRATCH (CSR_SCRATCH is anyways zero since we're in kernel).

Please see Links for additional relevant disccussion and alternative solution.

Tested by echo EXHAUST_STACK > /sys/kernel/debug/provoke-crash/DIRECT Kernel crash log below

Insufficient stack space to handle exception!/debug/provoke-crash/DIRECT Task stack: [0xff20000010a98000..0xff20000010a9c000] Overflow stack: [0xff600001f7d98370..0xff600001f7d99370] CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 Hardware name: riscv-virtio,qemu (DT) epc : __memset+0x60/0xfc ra : recursive_loop+0x48/0xc6 [lkdtm] epc : ffffffff808de0e4 ra : ffffffff0163a752 sp : ff20000010a97e80 gp : ffffffff815c0330 tp : ff600000820ea280 t0 : ff20000010a97e88 t1 : 000000000000002e t2 : 3233206874706564 s0 : ff20000010a982b0 s1 : 0000000000000012 a0 : ff20000010a97e88 a1 : 0000000000000000 a2 : 0000000000000400 a3 : ff20000010a98288 a4 : 0000000000000000 a5 : 0000000000000000 a6 : fffffffffffe43f0 a7 : 00007fffffffffff s2 : ff20000010a97e88 s3 : ffffffff01644680 s4 : ff20000010a9be90 s5 : ff600000842ba6c0 s6 : 00aaaaaac29e42b0 s7 : 00fffffff0aa3684 s8 : 00aaaaaac2978040 s9 : 0000000000000065 s10: 00ffffff8a7cad10 s11: 00ffffff8a76a4e0 t3 : ffffffff815dbaf4 t4 : ffffffff815dbaf4 t5 : ffffffff815dbab8 t6 : ff20000010a9bb48 status: 0000000200000120 badaddr: ff20000010a97e88 cause: 000000000000000f Kernel panic - not syncing: Kernel stack overflow CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 Hardware name: riscv-virtio,qemu (DT) Call Trace: [] dump_backtrace+0x30/0x38 [] show_stack+0x40/0x4c [] dump_stack_lvl+0x44/0x5c [] dump_stack+0x18/0x20 [] panic+0x126/0x2fe [] walk_stackframe+0x0/0xf0 [] recursive_loop+0x48/0xc6 [lkdtm] SMP: stopping secondary CPUs ---[ end Kernel panic - not syncing: Kernel stack overflow ]---

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{
  "affected": [],
  "aliases": [
    "CVE-2023-52761"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-05-21T16:15:15Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: VMAP_STACK overflow detection thread-safe\n\ncommit 31da94c25aea (\"riscv: add VMAP_STACK overflow detection\") added\nsupport for CONFIG_VMAP_STACK. If overflow is detected, CPU switches to\n`shadow_stack` temporarily before switching finally to per-cpu\n`overflow_stack`.\n\nIf two CPUs/harts are racing and end up in over flowing kernel stack, one\nor both will end up corrupting each other state because `shadow_stack` is\nnot per-cpu. This patch optimizes per-cpu overflow stack switch by\ndirectly picking per-cpu `overflow_stack` and gets rid of `shadow_stack`.\n\nFollowing are the changes in this patch\n\n - Defines an asm macro to obtain per-cpu symbols in destination\n   register.\n - In entry.S, when overflow is detected, per-cpu overflow stack is\n   located using per-cpu asm macro. Computing per-cpu symbol requires\n   a temporary register. x31 is saved away into CSR_SCRATCH\n   (CSR_SCRATCH is anyways zero since we\u0027re in kernel).\n\nPlease see Links for additional relevant disccussion and alternative\nsolution.\n\nTested by `echo EXHAUST_STACK \u003e /sys/kernel/debug/provoke-crash/DIRECT`\nKernel crash log below\n\n Insufficient stack space to handle exception!/debug/provoke-crash/DIRECT\n Task stack:     [0xff20000010a98000..0xff20000010a9c000]\n Overflow stack: [0xff600001f7d98370..0xff600001f7d99370]\n CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34\n Hardware name: riscv-virtio,qemu (DT)\n epc : __memset+0x60/0xfc\n  ra : recursive_loop+0x48/0xc6 [lkdtm]\n epc : ffffffff808de0e4 ra : ffffffff0163a752 sp : ff20000010a97e80\n  gp : ffffffff815c0330 tp : ff600000820ea280 t0 : ff20000010a97e88\n  t1 : 000000000000002e t2 : 3233206874706564 s0 : ff20000010a982b0\n  s1 : 0000000000000012 a0 : ff20000010a97e88 a1 : 0000000000000000\n  a2 : 0000000000000400 a3 : ff20000010a98288 a4 : 0000000000000000\n  a5 : 0000000000000000 a6 : fffffffffffe43f0 a7 : 00007fffffffffff\n  s2 : ff20000010a97e88 s3 : ffffffff01644680 s4 : ff20000010a9be90\n  s5 : ff600000842ba6c0 s6 : 00aaaaaac29e42b0 s7 : 00fffffff0aa3684\n  s8 : 00aaaaaac2978040 s9 : 0000000000000065 s10: 00ffffff8a7cad10\n  s11: 00ffffff8a76a4e0 t3 : ffffffff815dbaf4 t4 : ffffffff815dbaf4\n  t5 : ffffffff815dbab8 t6 : ff20000010a9bb48\n status: 0000000200000120 badaddr: ff20000010a97e88 cause: 000000000000000f\n Kernel panic - not syncing: Kernel stack overflow\n CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34\n Hardware name: riscv-virtio,qemu (DT)\n Call Trace:\n [\u003cffffffff80006754\u003e] dump_backtrace+0x30/0x38\n [\u003cffffffff808de798\u003e] show_stack+0x40/0x4c\n [\u003cffffffff808ea2a8\u003e] dump_stack_lvl+0x44/0x5c\n [\u003cffffffff808ea2d8\u003e] dump_stack+0x18/0x20\n [\u003cffffffff808dec06\u003e] panic+0x126/0x2fe\n [\u003cffffffff800065ea\u003e] walk_stackframe+0x0/0xf0\n [\u003cffffffff0163a752\u003e] recursive_loop+0x48/0xc6 [lkdtm]\n SMP: stopping secondary CPUs\n ---[ end Kernel panic - not syncing: Kernel stack overflow ]---",
  "id": "GHSA-jgx8-h977-4wfh",
  "modified": "2024-05-21T18:31:20Z",
  "published": "2024-05-21T18:31:20Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-52761"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1493baaf09e3c1899959c8a107cd1207e16d1788"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/be97d0db5f44c0674480cb79ac6f5b0529b84c76"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/eff53aea3855f71992c043cebb1c00988c17ee20"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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