Bug 2540491 (CVE-2026-97415)

Summary: CVE-2026-97415 kernel: btrfs: tree-checker: validate names in ROOT_REF and ROOT_BACKREF
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Btrfs file system. When processing subvolume reference items, the file system fails to properly validate on-disk name lengths before reading them. A local user could exploit this vulnerability by mounting a maliciously crafted file system image and querying subvolume information, triggering out-of-bounds memory access. This flaw can cause memory corruption, potentially leading to a system crash and a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-24 17:00:22 UTC 
In the Linux kernel, the following vulnerability has been resolved:

btrfs: tree-checker: validate names in ROOT_REF and ROOT_BACKREF

ROOT_REF and ROOT_BACKREF items contain a struct btrfs_root_ref followed
by the subvolume name. Several readers assume that this layout is already
valid and then use the on-disk name length directly. A corrupted item can
therefore make those readers address bytes outside the item, and
BTRFS_IOC_GET_SUBVOL_INFO can copy too many bytes into its fixed-size UAPI
name buffer.

Validate ROOT_REF and ROOT_BACKREF items in tree-checker before any reader
uses them. Reject records that do not contain a non-empty name, whose
name_len does not exactly describe the remaining item payload, or whose
name exceeds BTRFS_NAME_LEN.

For BTRFS_IOC_GET_SUBVOL_INFO, copy only the validated on-disk name_len
instead of deriving the copy length from the item size. The ioctl result is
zeroed when allocated. That leaves the existing trailing zero byte
untouched.
Comment 1 Mauro Matteo Cascella 2026-09-29 10:30:12 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97415.mbox