CVE-2026-63883: serial: qcom_geni: fix kfifo underflow when flush precedes DMA completion IRQ

Published Jul 19, 2026
·
Updated

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

serial: qcomgeni: fix kfifo underflow when flush precedes DMA completion IRQ

When uartflushbuffer() runs before the DMA completion IRQ is delivered, the following race can occur (all steps serialized by uartportlock):

1. DMA starts: txremaining = N, kfifo contains N bytes 2. DMA completes in hardware; IRQ is pending but not yet delivered 3. uartflushbuffer() acquires the port lock and calls kfiforeset(), making kfifolen() = 0 while txremaining remains N 4. uartflushbuffer() releases the port lock 5. DMA IRQ fires; handletxdma() acquires the port lock and calls uartxmitadvance(uport, txremaining) on an empty kfifo

uartxmitadvance() increments kfifo->out by txremaining. Since kfiforeset() already set both in and out to 0, out wraps past in, causing kfifolen() to return UARTXMITSIZE - txremaining. The next starttxdma() call then submits a DMA transfer of stale buffer data.

Fix this by snapshotting kfifolen() at the start of handletxdma() and skipping uartxmitadvance() when fifolen < txremaining, which indicates the kfifo was reset by a preceding flush.

Affected Software

161 affected componentsFixes available
Linux Kernel
ubuntu/linux-hwe-edge*
ubuntu/linux-aws-5.0*
ubuntu/linux-aws-5.3*
ubuntu/linux-azure*
ubuntu/linux-azure-5.3*
ubuntu/linux-azure-edge*
ubuntu/linux-gcp*
ubuntu/linux-gcp-5.3*
ubuntu/linux-gke-4.15*
ubuntu/linux-gke-5.4*
ubuntu/linux-gkeop-5.4*
ubuntu/linux-hwe*
ubuntu/linux-hwe-edge*
ubuntu/linux-oem*
ubuntu/linux-oracle-5.0*
ubuntu/linux-oracle-5.3*
ubuntu/linux-aws-5.11*
ubuntu/linux-aws-5.13*
ubuntu/linux-aws-5.8*
ubuntu/linux-azure-5.11*
ubuntu/linux-azure-5.13*
ubuntu/linux-azure-5.8*
ubuntu/linux-azure-fde*
ubuntu/linux-gcp-5.11*
ubuntu/linux-gcp-5.13*
ubuntu/linux-gcp-5.8*
ubuntu/linux-gke*
ubuntu/linux-gke-5.15*
ubuntu/linux-gkeop*
ubuntu/linux-gkeop-5.15*
ubuntu/linux-hwe-5.11*
ubuntu/linux-hwe-5.13*
ubuntu/linux-hwe-5.8*
ubuntu/linux-intel-5.13*
ubuntu/linux-oem-5.10*
ubuntu/linux-oem-5.13*
ubuntu/linux-oem-5.6*
ubuntu/linux-oracle-5.11*
ubuntu/linux-oracle-5.13*
ubuntu/linux-oracle-5.8*
ubuntu/linux-raspi2*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.11*
ubuntu/linux-riscv-5.8*
ubuntu/linux-allwinner-5.19*
ubuntu/linux-aws-5.19*
ubuntu/linux-aws-6.2*
ubuntu/linux-aws-6.5*
ubuntu/linux-aws-6.8<6.8.0-1066.69~22.04.1
6.8.0-1066.69~22.04.1
ubuntu/linux-azure-5.19*
ubuntu/linux-azure-6.2*
ubuntu/linux-azure-6.5*
ubuntu/linux-azure-6.8<6.8.0-1070.78~22.04.1
6.8.0-1070.78~22.04.1
ubuntu/linux-azure-fde-5.19*
ubuntu/linux-azure-fde-6.2*
ubuntu/linux-azure-fde-6.8<6.8.0-1068.75~22.04.1
6.8.0-1068.75~22.04.1
ubuntu/linux-gcp-5.19*
ubuntu/linux-gcp-6.2*
ubuntu/linux-gcp-6.5*
ubuntu/linux-gcp-6.8<6.8.0-1070.78~22.04.1
6.8.0-1070.78~22.04.1
ubuntu/linux-hwe-5.19*
ubuntu/linux-hwe-6.2*
ubuntu/linux-hwe-6.5*
ubuntu/linux-ibm-6.8<6.8.0-1066.67~22.04.1
6.8.0-1066.67~22.04.1
ubuntu/linux-intel-iot-realtime*
ubuntu/linux-lowlatency-hwe-5.19*
ubuntu/linux-lowlatency-hwe-6.2*
ubuntu/linux-lowlatency-hwe-6.5*
ubuntu/linux-lowlatency-hwe-6.8<6.8.0-146.146.1~22.04.1
6.8.0-146.146.1~22.04.1
ubuntu/linux-nvidia-6.2*
ubuntu/linux-nvidia-6.5*
ubuntu/linux-nvidia-6.8<6.8.0-1064.67~22.04.1
6.8.0-1064.67~22.04.1
ubuntu/linux-oem-5.17*
ubuntu/linux-oem-6.0*
ubuntu/linux-oem-6.1*
ubuntu/linux-oem-6.5*
ubuntu/linux-oracle-6.5*
ubuntu/linux-oracle-6.8*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.19*
ubuntu/linux-riscv-6.5*
ubuntu/linux-riscv-6.8<6.8.0-146.146~22.04.1
6.8.0-146.146~22.04.1
ubuntu/linux-starfive-5.19*
ubuntu/linux-starfive-6.2*
ubuntu/linux-starfive-6.5*
ubuntu/linux-realtime-6.8<6.8.1-1061.62~22.04.1
6.8.1-1061.62~22.04.1
ubuntu/linux<6.8.0-146.146
6.8.0-146.146
ubuntu/linux-aws<6.8.0-1066.69
6.8.0-1066.69
ubuntu/linux-aws-6.14*
ubuntu/linux-aws-6.17*
ubuntu/linux-azure<6.8.0-1070.78
6.8.0-1070.78
ubuntu/linux-azure-6.11*
ubuntu/linux-azure-6.14*
ubuntu/linux-azure-6.17*
ubuntu/linux-azure-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-azure-fde<6.8.0-1068.75
6.8.0-1068.75
ubuntu/linux-azure-fde-6.14*
ubuntu/linux-azure-fde-6.17*
ubuntu/linux-azure-fde-7.0<7.0.0-1013.13~24.04.1
7.0.0-1013.13~24.04.1
ubuntu/linux-azure-nvidia*
ubuntu/linux-azure-nvidia-6.14*
ubuntu/linux-gcp<6.8.0-1070.78
6.8.0-1070.78
ubuntu/linux-gcp-6.11*
ubuntu/linux-gcp-6.14*
ubuntu/linux-gcp-7.0<7.0.0-1011.11~24.04.1
7.0.0-1011.11~24.04.1
ubuntu/linux-gke<6.8.0-1065.73
6.8.0-1065.73
ubuntu/linux-gkeop<6.8.0-1051.55
6.8.0-1051.55
ubuntu/linux-hwe-6.11*
ubuntu/linux-hwe-6.14*
ubuntu/linux-hwe-6.17*
ubuntu/linux-hwe-7.0<7.0.0-28.28~24.04.1
7.0.0-28.28~24.04.1
ubuntu/linux-ibm<6.8.0-1066.67
6.8.0-1066.67
ubuntu/linux-lowlatency<6.8.0-146.146.1
6.8.0-146.146.1
ubuntu/linux-lowlatency-hwe-6.11*
ubuntu/linux-nvidia<6.8.0-1064.67
6.8.0-1064.67
ubuntu/linux-nvidia-6.11*
ubuntu/linux-nvidia-6.17*
ubuntu/linux-nvidia-7.0<7.0.0-1016.16~24.04.1
7.0.0-1016.16~24.04.1
ubuntu/linux-nvidia-lowlatency<6.8.0-1064.67.1
6.8.0-1064.67.1
ubuntu/linux-nvidia-tegra*
ubuntu/linux-oem-6.11*
ubuntu/linux-oem-6.14*
ubuntu/linux-oem-6.17*
ubuntu/linux-oem-6.8*
ubuntu/linux-oracle<6.8.0-1063.66
6.8.0-1063.66
ubuntu/linux-oracle-6.14*
ubuntu/linux-oracle-6.17*
ubuntu/linux-oracle-7.0<7.0.0-1011.11~24.04.1
7.0.0-1011.11~24.04.1
ubuntu/linux-raspi*
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-6.14*
ubuntu/linux-riscv-6.17*
ubuntu/linux-riscv-7.0<7.0.0-28.28.1~24.04.3
7.0.0-28.28.1~24.04.3
ubuntu/linux-xilinx*
ubuntu/linux-bluefield<6.8.0-1032.37
6.8.0-1032.37
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime<6.8.1-1061.62
6.8.1-1061.62
ubuntu/linux-realtime-6.14*
ubuntu/linux-realtime-6.17*
ubuntu/linux-aws-fips<6.8.0-1066.69+fips1
6.8.0-1066.69+fips1
ubuntu/linux-azure-fips<6.8.0-1069.77+fips1
6.8.0-1069.77+fips1
ubuntu/linux-fips<6.8.0-146.146+fips1
6.8.0-146.146+fips1
ubuntu/linux-gcp-fips<6.8.0-1070.78+fips1
6.8.0-1070.78+fips1
ubuntu/linux<7.0.0-28.28
7.0.0-28.28
ubuntu/linux-aws<7.0.0-1009.9
7.0.0-1009.9
ubuntu/linux-azure<7.0.0-1010.10
7.0.0-1010.10
ubuntu/linux-azure-fde<7.0.0-1009.9
7.0.0-1009.9
ubuntu/linux-gcp<7.0.0-1008.8
7.0.0-1008.8
ubuntu/linux-gke<7.0.0-1003.4
7.0.0-1003.4
ubuntu/linux-ibm<7.0.0-1010.10
7.0.0-1010.10
ubuntu/linux-nvidia<7.0.0-1016.16
7.0.0-1016.16
ubuntu/linux-nvidia-bos<7.0.0-2016.16
7.0.0-2016.16
ubuntu/linux-oem-7.0<7.0.0-1009.9
7.0.0-1009.9
ubuntu/linux-oracle<7.0.0-1008.8
7.0.0-1008.8
ubuntu/linux-raspi<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-realtime<7.0.0-28.28.1
7.0.0-28.28.1
ubuntu/linux-riscv<7.0.0-28.28.1
7.0.0-28.28.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.69~22.04.1
  2. Upgrade

    Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78~22.04.1
  3. Upgrade

    Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1068.75~22.04.1
  4. Upgrade

    Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78~22.04.1
  5. Upgrade

    Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.67~22.04.1
  6. Upgrade

    Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146.1~22.04.1
  7. Upgrade

    Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1064.67~22.04.1
  8. Upgrade

    Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146~22.04.1
  9. Upgrade

    Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.1-1061.62~22.04.1
  10. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146
  11. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.69
  12. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78
  13. Upgrade

    Upgrade ubuntu/linux-azure-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  14. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 6.8.0-1068.75
  15. Upgrade

    Upgrade ubuntu/linux-azure-fde-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13~24.04.1
  16. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78
  17. Upgrade

    Upgrade ubuntu/linux-gcp-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1011.11~24.04.1
  18. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 6.8.0-1065.73
  19. Upgrade

    Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.

    Fixed in 6.8.0-1051.55
  20. Upgrade

    Upgrade ubuntu/linux-hwe-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28~24.04.1
  21. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.67
  22. Upgrade

    Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146.1
  23. Upgrade

    Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.

    Fixed in 6.8.0-1064.67
  24. Upgrade

    Upgrade ubuntu/linux-nvidia-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16~24.04.1
  25. Upgrade

    Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.

    Fixed in 6.8.0-1064.67.1
  26. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 6.8.0-1063.66
  27. Upgrade

    Upgrade ubuntu/linux-oracle-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1011.11~24.04.1
  28. Upgrade

    Upgrade ubuntu/linux-riscv-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28.1~24.04.3
  29. Upgrade

    Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.

    Fixed in 6.8.0-1032.37
  30. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 6.8.1-1061.62
  31. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.69+fips1
  32. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1069.77+fips1
  33. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146+fips1
  34. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78+fips1
  35. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28
  36. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 7.0.0-1009.9
  37. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 7.0.0-1010.10
  38. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 7.0.0-1009.9
  39. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 7.0.0-1008.8
  40. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 7.0.0-1003.4
  41. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 7.0.0-1010.10
  42. Upgrade

    Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16
  43. Upgrade

    Upgrade ubuntu/linux-nvidia-bos to a version that resolves this vulnerability.

    Fixed in 7.0.0-2016.16
  44. Upgrade

    Upgrade ubuntu/linux-oem-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1009.9
  45. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 7.0.0-1008.8
  46. Upgrade

    Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  47. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28.1
  48. Upgrade

    Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28.1

Event History

Jul 19, 2026
CVE Published
via MITRE·02:54 PM
Data Sourced
via MITRE·02:54 PM
DescriptionSeverity
Data Sourced
via NVD·04:17 PM
DescriptionSeverity
Jul 20, 2026
Data Sourced
via OSV·12:00 AM
DescriptionSeverityAffected Software

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