CVE-2025-21709: kernel: be more careful about dup_mmap() failures and uprobe registering
In the Linux kernel, the following vulnerability has been resolved:
kernel: be more careful about dupmmap() failures and uprobe registering
If a memory allocation fails during dupmmap(), the maple tree can be left in an unsafe state for other iterators besides the exit path. All the locks are dropped before the exitmmap() call (in mm/mmap.c), but the incomplete mmstruct can be reached through (at least) the rmap finding the vmas which have a pointer back to the mmstruct.
Up to this point, there have been no issues with being able to find an mmstruct that was only partially initialised. Syzbot was able to make the incomplete mmstruct fail with recent forking changes, so it has been proven unsafe to use the mmstruct that hasn't been initialised, as referenced in the link below.
Although 8ac662f5da19f ("fork: avoid inappropriate uprobe access to invalid mm") fixed the uprobe access, it does not completely remove the race.
This patch sets the MMFOOMSKIP to avoid the iteration of the vmas on the oom side (even though this is extremely unlikely to be selected as an oom victim in the race window), and sets MMFUNSTABLE to avoid other potential users from using a partially initialised mmstruct.
When registering vmas for uprobe, skip the vmas in an mm that is marked unstable. Modifying a vma in an unstable mm may cause issues if the mm isn't fully initialised.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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ubuntu/linux-aws-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1061.64~22.04.1 - Upgrade
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ubuntu/linux-azure-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1063.71~22.04.1 - Upgrade
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ubuntu/linux-azure-fde-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1062.69~22.04.1 - Upgrade
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ubuntu/linux-gcp-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1064.72~22.04.1 - Upgrade
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ubuntu/linux-hwe-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-136.136~22.04.1 - Upgrade
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ubuntu/linux-ibm-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1061.62~22.04.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-136.136.2~22.04.1 - Upgrade
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ubuntu/linux-nvidia-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1059.62~22.04.1 - Upgrade
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ubuntu/linux-oracle-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1058.61~22.04.1 - Upgrade
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ubuntu/linux-riscv-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-136.136~22.04.3 - Upgrade
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ubuntu/linux-realtime-6.8to a version that resolves this vulnerability.Fixed in 6.8.1-1056.57~22.04.2 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-136.136 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1061.64 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1063.71 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 6.8.0-1062.69 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1064.72 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1059.67 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1046.50 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1061.62 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-136.136.2 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 6.8.0-1059.62 - Upgrade
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ubuntu/linux-nvidia-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-1059.62.1 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 6.8.0-1030.31 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1058.61 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 6.8.0-1061.65 - Upgrade
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ubuntu/linux-vmwareto a version that resolves this vulnerability.Fixed in 6.8.0-1008.8 - Upgrade
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ubuntu/linux-xilinxto a version that resolves this vulnerability.Fixed in 6.8.0-1033.34 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1028.33 - Upgrade
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ubuntu/linux-raspi-realtimeto a version that resolves this vulnerability.Fixed in 6.8.0-2050.52 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1056.57 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1061.64+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1063.71+fips2 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-136.136+fips2 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1064.72+fips1 - Configuration
Set MMF_OOM_SKIP to prevent OOM-side VMA iteration and set MMF_UNSTABLE to prevent other users from accessing a partially initialized mm_struct.
Linux kernel mm_struct handling MMF_OOM_SKIP and MMF_UNSTABLE = set for partially initialized mm_struct instances - Configuration
When registering VMAs for uprobes, skip VMAs belonging to an mm_struct marked unstable.
Linux kernel uprobe VMA registration unstable mm VMA registration = skip
Event History
Frequently Asked Questions
What is the severity of CVE-2025-21709?
CVE-2025-21709 has a moderate severity level due to potential unsafe states in the maple tree structure if memory allocation fails.
How do I fix CVE-2025-21709?
Fix CVE-2025-21709 by updating to the latest version of the Linux Kernel where the vulnerability has been resolved.
Who is affected by CVE-2025-21709?
CVE-2025-21709 affects systems running the Linux Kernel, particularly those that may experience memory allocation failure during dup_mmap().
What causes the vulnerability CVE-2025-21709?
CVE-2025-21709 is caused by improper handling of memory allocation failures in the dup_mmap() function, potentially leaving the maple tree in an unsafe state.
Is CVE-2025-21709 a local or remote vulnerability?
CVE-2025-21709 is considered a local vulnerability, as it requires local access to the affected system to exploit.