FKIE_CVE-2026-98118

Vulnerability from fkie_nvd - Published: 2026-09-25 11:17 - Updated: 2026-09-25 11:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: netfs: Fix readahead synchronisation issues by loading all folios upfront There are some synchronisation issues that derive from the app thread adding more folios to the rolling buffer whilst the collector thread is looking at them or trying to clear them, such as determining the setting of front_folio_order when the next folio hasn't been added yet, The reason for the rolling buffer approach is that loading the buffer upfront and then dropping all the refs just acquired is quite a slow operation, and loading progressively allows some of the cost to be deferred until after at least some of the I/O is started. Instead, a better way is to load all the folios into the rolling buffer upfront - and then drop the refs later, once the I/O is in progress. (Even better would be for the refs not to be there at all.) Fix this by changing the rolling buffer loader to load all the folios selected by the VM for readahead upfront into the folio queue. The folio queue is allocated a batch worth at a time as we don't know how many folios are involved (the readahead_control struct, alas, has a page count, not a folio count). The folio refs acquired from readahead are then dropped in bulk once the first subrequest is dispatched as it's quite a slow operation. The collector waits for NETFS_RREQ_NEED_PUT_RA_REFS to be cleared so that it doesn't unlock folios before the xarray has been scanned for them. This simplifies the buffer handling later and isn't noticeably slower as the xarray doesn't need to be modified and the folios are all already pre-locked.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8c9b33945712074a85d3bdacbca036ba6b3d92c6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fed0b33e6c584986ba70018ec9f9787a98216e64
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/netfs/buffered_read.c",
            "fs/netfs/internal.h",
            "fs/netfs/misc.c",
            "fs/netfs/read_collect.c",
            "fs/netfs/read_retry.c",
            "fs/netfs/rolling_buffer.c",
            "include/linux/netfs.h",
            "include/linux/rolling_buffer.h",
            "include/trace/events/netfs.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "8c9b33945712074a85d3bdacbca036ba6b3d92c6",
              "status": "affected",
              "version": "ee4cdf7ba857a894ad1650d6ab77669cbbfa329e",
              "versionType": "git"
            },
            {
              "lessThan": "fed0b33e6c584986ba70018ec9f9787a98216e64",
              "status": "affected",
              "version": "ee4cdf7ba857a894ad1650d6ab77669cbbfa329e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/netfs/buffered_read.c",
            "fs/netfs/internal.h",
            "fs/netfs/misc.c",
            "fs/netfs/read_collect.c",
            "fs/netfs/read_retry.c",
            "fs/netfs/rolling_buffer.c",
            "include/linux/netfs.h",
            "include/linux/rolling_buffer.h",
            "include/trace/events/netfs.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.12"
            },
            {
              "lessThan": "6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc3",
              "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\nnetfs: Fix readahead synchronisation issues by loading all folios upfront\n\nThere are some synchronisation issues that derive from the app thread\nadding more folios to the rolling buffer whilst the collector thread is\nlooking at them or trying to clear them, such as determining the setting of\nfront_folio_order when the next folio hasn\u0027t been added yet,\n\nThe reason for the rolling buffer approach is that loading the buffer\nupfront and then dropping all the refs just acquired is quite a slow\noperation, and loading progressively allows some of the cost to be deferred\nuntil after at least some of the I/O is started.\n\nInstead, a better way is to load all the folios into the rolling buffer\nupfront - and then drop the refs later, once the I/O is in progress.  (Even\nbetter would be for the refs not to be there at all.)\n\nFix this by changing the rolling buffer loader to load all the folios\nselected by the VM for readahead upfront into the folio queue.  The folio\nqueue is allocated a batch worth at a time as we don\u0027t know how many folios\nare involved (the readahead_control struct, alas, has a page count, not a\nfolio count).\n\nThe folio refs acquired from readahead are then dropped in bulk once the\nfirst subrequest is dispatched as it\u0027s quite a slow operation.  The\ncollector waits for NETFS_RREQ_NEED_PUT_RA_REFS to be cleared so that it\ndoesn\u0027t unlock folios before the xarray has been scanned for them.\n\nThis simplifies the buffer handling later and isn\u0027t noticeably slower as\nthe xarray doesn\u0027t need to be modified and the folios are all already\npre-locked."
    }
  ],
  "id": "CVE-2026-98118",
  "lastModified": "2026-09-25T11:17:43.030",
  "metrics": {},
  "published": "2026-09-25T11:17:43.030",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8c9b33945712074a85d3bdacbca036ba6b3d92c6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/fed0b33e6c584986ba70018ec9f9787a98216e64"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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