CVE-2022-50849 (GCVE-0-2022-50849)

Vulnerability from cvelistv5 – Published: 2025-12-30 12:15 – Updated: 2025-12-30 12:15
VLAI?
Title
pstore: Avoid kcore oops by vmap()ing with VM_IOREMAP
Summary
In the Linux kernel, the following vulnerability has been resolved: pstore: Avoid kcore oops by vmap()ing with VM_IOREMAP An oops can be induced by running 'cat /proc/kcore > /dev/null' on devices using pstore with the ram backend because kmap_atomic() assumes lowmem pages are accessible with __va(). Unable to handle kernel paging request at virtual address ffffff807ff2b000 Mem abort info: ESR = 0x96000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x06: level 2 translation fault Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000081d87000 [ffffff807ff2b000] pgd=180000017fe18003, p4d=180000017fe18003, pud=180000017fe18003, pmd=0000000000000000 Internal error: Oops: 96000006 [#1] PREEMPT SMP Modules linked in: dm_integrity CPU: 7 PID: 21179 Comm: perf Not tainted 5.15.67-10882-ge4eb2eb988cd #1 baa443fb8e8477896a370b31a821eb2009f9bfba Hardware name: Google Lazor (rev3 - 8) (DT) pstate: a0400009 (NzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : __memcpy+0x110/0x260 lr : vread+0x194/0x294 sp : ffffffc013ee39d0 x29: ffffffc013ee39f0 x28: 0000000000001000 x27: ffffff807ff2b000 x26: 0000000000001000 x25: ffffffc0085a2000 x24: ffffff802d4b3000 x23: ffffff80f8a60000 x22: ffffff802d4b3000 x21: ffffffc0085a2000 x20: ffffff8080b7bc68 x19: 0000000000001000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: ffffffd3073f2e60 x14: ffffffffad588000 x13: 0000000000000000 x12: 0000000000000001 x11: 00000000000001a2 x10: 00680000fff2bf0b x9 : 03fffffff807ff2b x8 : 0000000000000001 x7 : 0000000000000000 x6 : 0000000000000000 x5 : ffffff802d4b4000 x4 : ffffff807ff2c000 x3 : ffffffc013ee3a78 x2 : 0000000000001000 x1 : ffffff807ff2b000 x0 : ffffff802d4b3000 Call trace: __memcpy+0x110/0x260 read_kcore+0x584/0x778 proc_reg_read+0xb4/0xe4 During early boot, memblock reserves the pages for the ramoops reserved memory node in DT that would otherwise be part of the direct lowmem mapping. Pstore's ram backend reuses those reserved pages to change the memory type (writeback or non-cached) by passing the pages to vmap() (see pfn_to_page() usage in persistent_ram_vmap() for more details) with specific flags. When read_kcore() starts iterating over the vmalloc region, it runs over the virtual address that vmap() returned for ramoops. In aligned_vread() the virtual address is passed to vmalloc_to_page() which returns the page struct for the reserved lowmem area. That lowmem page is passed to kmap_atomic(), which effectively calls page_to_virt() that assumes a lowmem page struct must be directly accessible with __va() and friends. These pages are mapped via vmap() though, and the lowmem mapping was never made, so accessing them via the lowmem virtual address oopses like above. Let's side-step this problem by passing VM_IOREMAP to vmap(). This will tell vread() to not include the ramoops region in the kcore. Instead the area will look like a bunch of zeros. The alternative is to teach kmap() about vmalloc areas that intersect with lowmem. Presumably such a change isn't a one-liner, and there isn't much interest in inspecting the ramoops region in kcore files anyway, so the most expedient route is taken for now.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 404a6043385de17273624b076599669db5ad891f , < 1579bed1613802a323a1e14567faa95c149e105e (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < fdebcc33b663d2e8da937653ddfbfc1315047eaa (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < 6d9460214e363e1f3d0756ee5d947e76e3e6f86c (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < 4d3126f242a0090342ffe925c35fb4f4252b7562 (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < 295f59cd2cdeed841850d02dddde3a122cbf6fc6 (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < ebc73c4f266281e2cad1a372ecd81572d95375b6 (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < 69dbff7d2681c55a4d979fd9b75576303e69979f (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < 2f82381d0681b10f9ddd27be98c27363b5a3cd1c (git)
Affected: 404a6043385de17273624b076599669db5ad891f , < e6b842741b4f39007215fd7e545cb55aa3d358a2 (git)
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    Linux Linux Affected: 3.4
Unaffected: 0 , < 3.4 (semver)
Unaffected: 4.9.337 , ≤ 4.9.* (semver)
Unaffected: 4.14.303 , ≤ 4.14.* (semver)
Unaffected: 4.19.270 , ≤ 4.19.* (semver)
Unaffected: 5.4.229 , ≤ 5.4.* (semver)
Unaffected: 5.10.163 , ≤ 5.10.* (semver)
Unaffected: 5.15.86 , ≤ 5.15.* (semver)
Unaffected: 6.0.16 , ≤ 6.0.* (semver)
Unaffected: 6.1.2 , ≤ 6.1.* (semver)
Unaffected: 6.2 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "fs/pstore/ram_core.c"
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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\npstore: Avoid kcore oops by vmap()ing with VM_IOREMAP\n\nAn oops can be induced by running \u0027cat /proc/kcore \u003e /dev/null\u0027 on\ndevices using pstore with the ram backend because kmap_atomic() assumes\nlowmem pages are accessible with __va().\n\n Unable to handle kernel paging request at virtual address ffffff807ff2b000\n Mem abort info:\n ESR = 0x96000006\n EC = 0x25: DABT (current EL), IL = 32 bits\n SET = 0, FnV = 0\n EA = 0, S1PTW = 0\n FSC = 0x06: level 2 translation fault\n Data abort info:\n ISV = 0, ISS = 0x00000006\n CM = 0, WnR = 0\n swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000081d87000\n [ffffff807ff2b000] pgd=180000017fe18003, p4d=180000017fe18003, pud=180000017fe18003, pmd=0000000000000000\n Internal error: Oops: 96000006 [#1] PREEMPT SMP\n Modules linked in: dm_integrity\n CPU: 7 PID: 21179 Comm: perf Not tainted 5.15.67-10882-ge4eb2eb988cd #1 baa443fb8e8477896a370b31a821eb2009f9bfba\n Hardware name: Google Lazor (rev3 - 8) (DT)\n pstate: a0400009 (NzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)\n pc : __memcpy+0x110/0x260\n lr : vread+0x194/0x294\n sp : ffffffc013ee39d0\n x29: ffffffc013ee39f0 x28: 0000000000001000 x27: ffffff807ff2b000\n x26: 0000000000001000 x25: ffffffc0085a2000 x24: ffffff802d4b3000\n x23: ffffff80f8a60000 x22: ffffff802d4b3000 x21: ffffffc0085a2000\n x20: ffffff8080b7bc68 x19: 0000000000001000 x18: 0000000000000000\n x17: 0000000000000000 x16: 0000000000000000 x15: ffffffd3073f2e60\n x14: ffffffffad588000 x13: 0000000000000000 x12: 0000000000000001\n x11: 00000000000001a2 x10: 00680000fff2bf0b x9 : 03fffffff807ff2b\n x8 : 0000000000000001 x7 : 0000000000000000 x6 : 0000000000000000\n x5 : ffffff802d4b4000 x4 : ffffff807ff2c000 x3 : ffffffc013ee3a78\n x2 : 0000000000001000 x1 : ffffff807ff2b000 x0 : ffffff802d4b3000\n Call trace:\n __memcpy+0x110/0x260\n read_kcore+0x584/0x778\n proc_reg_read+0xb4/0xe4\n\nDuring early boot, memblock reserves the pages for the ramoops reserved\nmemory node in DT that would otherwise be part of the direct lowmem\nmapping. Pstore\u0027s ram backend reuses those reserved pages to change the\nmemory type (writeback or non-cached) by passing the pages to vmap()\n(see pfn_to_page() usage in persistent_ram_vmap() for more details) with\nspecific flags. When read_kcore() starts iterating over the vmalloc\nregion, it runs over the virtual address that vmap() returned for\nramoops. In aligned_vread() the virtual address is passed to\nvmalloc_to_page() which returns the page struct for the reserved lowmem\narea. That lowmem page is passed to kmap_atomic(), which effectively\ncalls page_to_virt() that assumes a lowmem page struct must be directly\naccessible with __va() and friends. These pages are mapped via vmap()\nthough, and the lowmem mapping was never made, so accessing them via the\nlowmem virtual address oopses like above.\n\nLet\u0027s side-step this problem by passing VM_IOREMAP to vmap(). This will\ntell vread() to not include the ramoops region in the kcore. Instead the\narea will look like a bunch of zeros. The alternative is to teach kmap()\nabout vmalloc areas that intersect with lowmem. Presumably such a change\nisn\u0027t a one-liner, and there isn\u0027t much interest in inspecting the\nramoops region in kcore files anyway, so the most expedient route is\ntaken for now."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-30T12:15:26.431Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1579bed1613802a323a1e14567faa95c149e105e"
        },
        {
          "url": "https://git.kernel.org/stable/c/fdebcc33b663d2e8da937653ddfbfc1315047eaa"
        },
        {
          "url": "https://git.kernel.org/stable/c/6d9460214e363e1f3d0756ee5d947e76e3e6f86c"
        },
        {
          "url": "https://git.kernel.org/stable/c/4d3126f242a0090342ffe925c35fb4f4252b7562"
        },
        {
          "url": "https://git.kernel.org/stable/c/295f59cd2cdeed841850d02dddde3a122cbf6fc6"
        },
        {
          "url": "https://git.kernel.org/stable/c/ebc73c4f266281e2cad1a372ecd81572d95375b6"
        },
        {
          "url": "https://git.kernel.org/stable/c/69dbff7d2681c55a4d979fd9b75576303e69979f"
        },
        {
          "url": "https://git.kernel.org/stable/c/2f82381d0681b10f9ddd27be98c27363b5a3cd1c"
        },
        {
          "url": "https://git.kernel.org/stable/c/e6b842741b4f39007215fd7e545cb55aa3d358a2"
        }
      ],
      "title": "pstore: Avoid kcore oops by vmap()ing with VM_IOREMAP",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2022-50849",
    "datePublished": "2025-12-30T12:15:26.431Z",
    "dateReserved": "2025-12-30T12:06:07.134Z",
    "dateUpdated": "2025-12-30T12:15:26.431Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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