UBUNTU-CVE-2026-72215: Medium severity ubuntu/linux vulnerability
In the Linux kernel, the following vulnerability has been resolved: MIPS: DEC: Ensure 32-bit stack location for o32 promprintf() In 64-bit configurations calling any firmware entry points from a kernel thread other than the initial one will result in a situation where the stack has been placed in the XKPHYS 64-bit memory segment. Consequently the stack pointer is no longer a 32-bit value and when the 32-bit firmware code called uses 32-bit ALU operations to manipulate the stack pointer, the calculated result is incorrect (in fact in the 64-bit MIPS ISA almost all 32-bit ALU operations will produce an unpredictable result when executed on 64-bit data) and control goes astray. This may happen when no final console driver has been enabled in the configuration and consequently the initial console continues being used late into bootstrap, or with an upcoming change that will switch the zs driver to use a platform device, which in turn will make the console handover happen only after other kernel threads have already been started, and the kernel will hang at: pidmax: default: 32768 minimum: 301 or somewhat later, but always before: cblistinitgeneric: Setting adjustable number of callback queues. has been printed. It seems that only the promprintf() entry point is affected. Of all the other entry points wired only rexslotaddress() and rexgettcinfo() are called from a kernel thread other than the initial one, specifically kernelinit(), and they are leaf functions that do no business with the stack, having worked with no issue ever since 64-bit support was added for the platform back in 2002. To address this issue then, arrange for the stack to be switched in the o32 wrapper as required for promprintf() only, by supplying callo32() with a pointer to a chunk of initdata space, which is placed in the CKSEG0 32-bit compatibility segment, observing that promprintf() is only called from console output handler and therefore with the console lock held, implying no need for this code to be reentrant. Other firmware entry points may be called with interrupts enabled and no lock held, and may therefore require that callo32() be reentrant. They trigger no issue at this point and "if it ain't broke, don't fix it," so just leave them alone.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1117.124~20.04.1 - Upgrade
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ubuntu/linux-azure-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1123.132~20.04.1 - Upgrade
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ubuntu/linux-azure-fde-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1122.131~20.04.1 - Upgrade
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ubuntu/linux-gcp-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1118.128~20.04.1 - Upgrade
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ubuntu/linux-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-198.208~20.04.1 - Upgrade
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ubuntu/linux-ibm-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linux-intel-iotg-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1112.118~20.04.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-195.205~20.04.1 - Upgrade
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ubuntu/linux-oracle-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1114.120~20.04.1 - Upgrade
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ubuntu/linux-riscv-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 5.15.0-198.208 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 5.15.0-1122.131 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 5.15.0-1113.119 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 5.15.0-1100.108 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 5.15.0-1111.115 - Upgrade
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ubuntu/linux-intel-iotgto a version that resolves this vulnerability.Fixed in 5.15.0-1112.118 - Upgrade
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ubuntu/linux-kvmto a version that resolves this vulnerability.Fixed in 5.15.0-1109.114 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 5.15.0-195.205 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 5.15.0-1112.113 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 5.15.0-1114.120 - Upgrade
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ubuntu/linux-xilinx-zynqmpto a version that resolves this vulnerability.Fixed in 5.15.0-1080.84 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 5.15.0-1101.103 - Upgrade
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ubuntu/linux-intel-iot-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1109.111 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1116.125 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-198.208+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-147.147 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17~24.04.1 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 6.8.0-1069.76 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.16~24.04.1 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1066.74 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1052.56 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38~24.04.4 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1067.68 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-147.147.1 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1064.67 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1~24.04.1 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1033.38 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1062.63 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-147.147+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1008.9 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
For MIPS 64-bit configurations, switch the stack in the o32 wrapper for prom_printf() by supplying call_o32() with a pointer to a chunk of initdata space located in the CKSEG0 32-bit compatibility segment.
Event History
Frequently Asked Questions
Which deployments are realistically exposed to this issue?
The issue applies to 64-bit MIPS DEC configurations that invoke 32-bit firmware entry points from a kernel thread other than the initial thread. The affected Ubuntu kernel packages listed are linux, linux-fips, linux-aws, linux-azure, linux-aws-fips, linux-azure-fips, linux-gcp, and linux-gcp-fips.
What conditions trigger the failure?
A firmware call must occur while the calling kernel thread has its stack in the XKPHYS 64-bit memory segment. The 32-bit firmware then manipulates a non-32-bit stack pointer with 32-bit ALU operations, causing incorrect control flow.
How might this appear during boot?
The kernel can hang during bootstrap, including at "pid_max: default: 32768 minimum: 301" or somewhat later, but before "cblist_init_generic: Setting adjustable number of call…". A delayed console handover can create the triggering condition, such as when no final console driver is enabled and the initial console remains in use late in boot.