CVE-2026-23249: xfs: check for deleted cursors when revalidating two btrees
In the Linux kernel, the following vulnerability has been resolved:
xfs: check for deleted cursors when revalidating two btrees
The free space and inode btree repair functions will rebuild both btrees at the same time, after which it needs to evaluate both btrees to confirm that the corruptions are gone.
However, Jiaming Zhang ran syzbot and produced a crash in the second xchkallocbt call. His root-cause analysis is as follows (with minor corrections):
In xreprevalidateallocbt(), xchkallocbt() is called twice (first for BNOBT, second for CNTBT). The cause of this issue is that the first call nullified the cursor required by the second call.
Let's first enter xreprevalidateallocbt() via following call chain:
xfsfileioctl() -> xfsiocscrubvmetadata() -> xfsscrubmetadata() -> sc->ops->repaireval(sc) -> xreprevalidateallocbt()
xchkallocbt() is called twice in this function. In the first call:
/ Note that sc->sm->smtype is XFSSCRUBTYPEBNOPT now / xchkallocbt() -> xchkbtree() -> bs->scrubrec(bs, recp) -> xchkallocbtrec() -> xchkallocbtxref() -> xchkallocbtxrefother()
since smtype is XFSSCRUBTYPEBNOBT, pur is set to &sc->sa.cntcur. Kernel called xfsallocgetrec() and returned -EFSCORRUPTED. Call chain:
xfsallocgetrec() -> xfsbtreegetrec() -> xfsbtreecheckblock() -> (XFSISCORRUPT || XFSTESTERROR), the former is false and the latter is true, return -EFSCORRUPTED. This should be caused by ioctl$XFSIOCERRORINJECTION I guess.
Back to xchkallocbtxrefother(), after receiving -EFSCORRUPTED from xfsallocgetrec(), kernel called xchkshouldcheckxref(). In this function, curpp (points to sc->sa.cntcur) is nullified.
Back to xreprevalidateallocbt(), since sc->sa.cntcur has been nullified, it then triggered null-ptr-deref via xchkallocbt() (second call) -> xchkbtree().
So. The bnobt revalidation failed on a cross-reference attempt, so we deleted the cntbt cursor, and then crashed when we tried to revalidate the cntbt. Therefore, check for a null cntbt cursor before that revalidation, and mark the repair incomplete. Also we can ignore the second tree entirely if the first tree was rebuilt but is already corrupt.
Apply the same fix to xreprevalidateiallocbt because it has the same problem.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.12.85-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.19.6-1 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.12.75 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.18.16 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.19.6 - Upgrade
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ubuntu/linux-aws-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1060.63~22.04.1 - 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 6.8.0-1063.69~22.04.1 - 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 6.8.0-1060.61~22.04.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-134.134.1~22.04.1 - Upgrade
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ubuntu/linux-nvidia-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-oracle-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1057.58~22.04.1 - Upgrade
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ubuntu/linux-riscv-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-134.134~22.04.1 - Upgrade
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ubuntu/linux-realtime-6.8to a version that resolves this vulnerability.Fixed in 6.8.1-1055.56~22.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-134.134 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1060.63 - Upgrade
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ubuntu/linux-azure-nvidiato a version that resolves this vulnerability.Fixed in 6.8.0-1039.42 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1063.69 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1058.64 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1045.48 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-134.134.1 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 6.8.0-1058.61 - Upgrade
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ubuntu/linux-nvidia-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-1058.61.1 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 6.8.0-1029.30 - Upgrade
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ubuntu/linux-xilinxto a version that resolves this vulnerability.Fixed in 6.8.0-1032.33 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1026.30 - Upgrade
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ubuntu/linux-raspi-realtimeto a version that resolves this vulnerability.Fixed in 6.8.0-2049.50 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1055.56 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1060.63+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1062.69+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-134.134+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1063.69+fips1 - 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 6.12.116-1Fixed in 7.2.15-1Fixed in 7.3.4-1 - Compensating control
In xrep_revalidate_allocbt() and xrep_revalidate_iallocbt(), check whether the cursor required for the second btree revalidation is null after the first btree check; if it is null, skip the second-tree revalidation and mark the repair incomplete. Also ignore the second tree when the first rebuilt tree is already corrupt.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-23249?
CVE-2026-23249 has been classified as a moderate severity vulnerability.
How do I fix CVE-2026-23249?
To fix CVE-2026-23249, update your Linux kernel to the latest version that includes the security patch.
What software is affected by CVE-2026-23249?
CVE-2026-23249 affects the Linux kernel, specifically the xfs filesystem components.
What does CVE-2026-23249 affect in the xfs filesystem?
CVE-2026-23249 affects the handling of deleted cursors during the revalidation of two btrees.
Is there any risk of data loss related to CVE-2026-23249?
There is a potential risk of data corruption if the vulnerability is exploited on a system using affected versions of the Linux kernel.