CVE-2022-49214 (GCVE-0-2022-49214)

Vulnerability from cvelistv5 – Published: 2025-02-26 01:55 – Updated: 2025-05-04 08:32
VLAI?
Title
powerpc/64s: Don't use DSISR for SLB faults
Summary
In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Don't use DSISR for SLB faults Since commit 46ddcb3950a2 ("powerpc/mm: Show if a bad page fault on data is read or write.") we use page_fault_is_write(regs->dsisr) in __bad_page_fault() to determine if the fault is for a read or write, and change the message printed accordingly. But SLB faults, aka Data Segment Interrupts, don't set DSISR (Data Storage Interrupt Status Register) to a useful value. All ISA versions from v2.03 through v3.1 specify that the Data Segment Interrupt sets DSISR "to an undefined value". As far as I can see there's no mention of SLB faults setting DSISR in any BookIV content either. This manifests as accesses that should be a read being incorrectly reported as writes, for example, using the xmon "dump" command: 0:mon> d 0x5deadbeef0000000 5deadbeef0000000 [359526.415354][ C6] BUG: Unable to handle kernel data access on write at 0x5deadbeef0000000 [359526.415611][ C6] Faulting instruction address: 0xc00000000010a300 cpu 0x6: Vector: 380 (Data SLB Access) at [c00000000ffbf400] pc: c00000000010a300: mread+0x90/0x190 If we disassemble the PC, we see a load instruction: 0:mon> di c00000000010a300 c00000000010a300 89490000 lbz r10,0(r9) We can also see in exceptions-64s.S that the data_access_slb block doesn't set IDSISR=1, which means it doesn't load DSISR into pt_regs. So the value we're using to determine if the fault is a read/write is some stale value in pt_regs from a previous page fault. Rework the printing logic to separate the SLB fault case out, and only print read/write in the cases where we can determine it. The result looks like eg: 0:mon> d 0x5deadbeef0000000 5deadbeef0000000 [ 721.779525][ C6] BUG: Unable to handle kernel data access at 0x5deadbeef0000000 [ 721.779697][ C6] Faulting instruction address: 0xc00000000014cbe0 cpu 0x6: Vector: 380 (Data SLB Access) at [c00000000ffbf390] 0:mon> d 0 0000000000000000 [ 742.793242][ C6] BUG: Kernel NULL pointer dereference at 0x00000000 [ 742.793316][ C6] Faulting instruction address: 0xc00000000014cbe0 cpu 0x6: Vector: 380 (Data SLB Access) at [c00000000ffbf390]
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 46ddcb3950a28c0df4815e8dbb8d4b91d5d9f22d , < 4a852ff9b7bea9c640540e2c1bc70bd3ba455d61 (git)
Affected: 46ddcb3950a28c0df4815e8dbb8d4b91d5d9f22d , < a3dae36d632b2cf6eb20314273e512a96cb43c9a (git)
Affected: 46ddcb3950a28c0df4815e8dbb8d4b91d5d9f22d , < 093449bb182db885dae816d62874cccab7a4c42a (git)
Affected: 46ddcb3950a28c0df4815e8dbb8d4b91d5d9f22d , < d4679ac8ea2e5078704aa1c026db36580cc1bf9a (git)
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    Linux Linux Affected: 5.5
Unaffected: 0 , < 5.5 (semver)
Unaffected: 5.15.33 , ≤ 5.15.* (semver)
Unaffected: 5.16.19 , ≤ 5.16.* (semver)
Unaffected: 5.17.2 , ≤ 5.17.* (semver)
Unaffected: 5.18 , ≤ * (original_commit_for_fix)
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          "programFiles": [
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/64s: Don\u0027t use DSISR for SLB faults\n\nSince commit 46ddcb3950a2 (\"powerpc/mm: Show if a bad page fault on data\nis read or write.\") we use page_fault_is_write(regs-\u003edsisr) in\n__bad_page_fault() to determine if the fault is for a read or write, and\nchange the message printed accordingly.\n\nBut SLB faults, aka Data Segment Interrupts, don\u0027t set DSISR (Data\nStorage Interrupt Status Register) to a useful value. All ISA versions\nfrom v2.03 through v3.1 specify that the Data Segment Interrupt sets\nDSISR \"to an undefined value\". As far as I can see there\u0027s no mention of\nSLB faults setting DSISR in any BookIV content either.\n\nThis manifests as accesses that should be a read being incorrectly\nreported as writes, for example, using the xmon \"dump\" command:\n\n  0:mon\u003e d 0x5deadbeef0000000\n  5deadbeef0000000\n  [359526.415354][    C6] BUG: Unable to handle kernel data access on write at 0x5deadbeef0000000\n  [359526.415611][    C6] Faulting instruction address: 0xc00000000010a300\n  cpu 0x6: Vector: 380 (Data SLB Access) at [c00000000ffbf400]\n      pc: c00000000010a300: mread+0x90/0x190\n\nIf we disassemble the PC, we see a load instruction:\n\n  0:mon\u003e di c00000000010a300\n  c00000000010a300 89490000      lbz     r10,0(r9)\n\nWe can also see in exceptions-64s.S that the data_access_slb block\ndoesn\u0027t set IDSISR=1, which means it doesn\u0027t load DSISR into pt_regs. So\nthe value we\u0027re using to determine if the fault is a read/write is some\nstale value in pt_regs from a previous page fault.\n\nRework the printing logic to separate the SLB fault case out, and only\nprint read/write in the cases where we can determine it.\n\nThe result looks like eg:\n\n  0:mon\u003e d 0x5deadbeef0000000\n  5deadbeef0000000\n  [  721.779525][    C6] BUG: Unable to handle kernel data access at 0x5deadbeef0000000\n  [  721.779697][    C6] Faulting instruction address: 0xc00000000014cbe0\n  cpu 0x6: Vector: 380 (Data SLB Access) at [c00000000ffbf390]\n\n  0:mon\u003e d 0\n  0000000000000000\n  [  742.793242][    C6] BUG: Kernel NULL pointer dereference at 0x00000000\n  [  742.793316][    C6] Faulting instruction address: 0xc00000000014cbe0\n  cpu 0x6: Vector: 380 (Data SLB Access) at [c00000000ffbf390]"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-05-04T08:32:31.260Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/4a852ff9b7bea9c640540e2c1bc70bd3ba455d61"
        },
        {
          "url": "https://git.kernel.org/stable/c/a3dae36d632b2cf6eb20314273e512a96cb43c9a"
        },
        {
          "url": "https://git.kernel.org/stable/c/093449bb182db885dae816d62874cccab7a4c42a"
        },
        {
          "url": "https://git.kernel.org/stable/c/d4679ac8ea2e5078704aa1c026db36580cc1bf9a"
        }
      ],
      "title": "powerpc/64s: Don\u0027t use DSISR for SLB faults",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2022-49214",
    "datePublished": "2025-02-26T01:55:49.677Z",
    "dateReserved": "2025-02-26T01:49:39.292Z",
    "dateUpdated": "2025-05-04T08:32:31.260Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}


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