FKIE_CVE-2026-63883

Vulnerability from fkie_nvd - Published: 2026-07-19 16:17 - Updated: 2026-07-20 15:16
Severity
7.3 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
Summary
In the Linux kernel, the following vulnerability has been resolved: serial: qcom_geni: fix kfifo underflow when flush precedes DMA completion IRQ When uart_flush_buffer() runs before the DMA completion IRQ is delivered, the following race can occur (all steps serialized by uart_port_lock): 1. DMA starts: tx_remaining = N, kfifo contains N bytes 2. DMA completes in hardware; IRQ is pending but not yet delivered 3. uart_flush_buffer() acquires the port lock and calls kfifo_reset(), making kfifo_len() = 0 while tx_remaining remains N 4. uart_flush_buffer() releases the port lock 5. DMA IRQ fires; handle_tx_dma() acquires the port lock and calls uart_xmit_advance(uport, tx_remaining) on an empty kfifo uart_xmit_advance() increments kfifo->out by tx_remaining. Since kfifo_reset() already set both in and out to 0, out wraps past in, causing kfifo_len() to return UART_XMIT_SIZE - tx_remaining. The next start_tx_dma() call then submits a DMA transfer of stale buffer data. Fix this by snapshotting kfifo_len() at the start of handle_tx_dma() and skipping uart_xmit_advance() when fifo_len < tx_remaining, which indicates the kfifo was reset by a preceding flush.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0d2c41a8b00934ddf8a7c1b4cf72dffa1e629c46
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/452d6fa37ae9b021f4f6d397dbae077f7296f6f4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/654f45a8569f3cd6ff20bd724a18e0cce65893ba
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b1159dce10b38eb795e4c96cdc4d34b83cec81c5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c91ea13375f70f6271a0183445e34e83b8f4d8f7
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/tty/serial/qcom_geni_serial.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "c91ea13375f70f6271a0183445e34e83b8f4d8f7",
              "status": "affected",
              "version": "2aaa43c7077833301c237684cd7bc9ae5e3dec95",
              "versionType": "git"
            },
            {
              "lessThan": "b1159dce10b38eb795e4c96cdc4d34b83cec81c5",
              "status": "affected",
              "version": "2aaa43c7077833301c237684cd7bc9ae5e3dec95",
              "versionType": "git"
            },
            {
              "lessThan": "654f45a8569f3cd6ff20bd724a18e0cce65893ba",
              "status": "affected",
              "version": "2aaa43c7077833301c237684cd7bc9ae5e3dec95",
              "versionType": "git"
            },
            {
              "lessThan": "0d2c41a8b00934ddf8a7c1b4cf72dffa1e629c46",
              "status": "affected",
              "version": "2aaa43c7077833301c237684cd7bc9ae5e3dec95",
              "versionType": "git"
            },
            {
              "lessThan": "452d6fa37ae9b021f4f6d397dbae077f7296f6f4",
              "status": "affected",
              "version": "2aaa43c7077833301c237684cd7bc9ae5e3dec95",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/tty/serial/qcom_geni_serial.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.3"
            },
            {
              "lessThan": "6.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "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\nserial: qcom_geni: fix kfifo underflow when flush precedes DMA completion IRQ\n\nWhen uart_flush_buffer() runs before the DMA completion IRQ is delivered,\nthe following race can occur (all steps serialized by uart_port_lock):\n\n  1. DMA starts: tx_remaining = N, kfifo contains N bytes\n  2. DMA completes in hardware; IRQ is pending but not yet delivered\n  3. uart_flush_buffer() acquires the port lock and calls kfifo_reset(),\n     making kfifo_len() = 0 while tx_remaining remains N\n  4. uart_flush_buffer() releases the port lock\n  5. DMA IRQ fires; handle_tx_dma() acquires the port lock and calls\n     uart_xmit_advance(uport, tx_remaining) on an empty kfifo\n\nuart_xmit_advance() increments kfifo-\u003eout by tx_remaining. Since\nkfifo_reset() already set both in and out to 0, out wraps past in,\ncausing kfifo_len() to return UART_XMIT_SIZE - tx_remaining. The next\nstart_tx_dma() call then submits a DMA transfer of stale buffer data.\n\nFix this by snapshotting kfifo_len() at the start of handle_tx_dma()\nand skipping uart_xmit_advance() when fifo_len \u003c tx_remaining, which\nindicates the kfifo was reset by a preceding flush."
    }
  ],
  "id": "CVE-2026-63883",
  "lastModified": "2026-07-20T15:16:53.603",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "LOW",
          "baseScore": 7.3,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.5,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T16:17:05.343",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0d2c41a8b00934ddf8a7c1b4cf72dffa1e629c46"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/452d6fa37ae9b021f4f6d397dbae077f7296f6f4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/654f45a8569f3cd6ff20bd724a18e0cce65893ba"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b1159dce10b38eb795e4c96cdc4d34b83cec81c5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c91ea13375f70f6271a0183445e34e83b8f4d8f7"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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