PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io()
Summary
| CVE | CVE-2026-89722 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-11 20:20:01 UTC |
| Updated | 2026-09-13 07:17:37 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io() pci_write_legacy_io() loads 4 bytes from the kernfs write buffer regardless of how many bytes userspace wrote: if (count != 1 && count != 2 && count != 4) return -EINVAL; return pci_legacy_write(bus, off, *(u32 *)buf, count); kernfs_fop_write_iter() allocates the buffer with kmalloc(len + 1), so a 1-byte write to the legacy_io sysfs file allocates 2 bytes and the unconditional u32 load reads up to 2 bytes past the end of the allocation, which KASAN reports as a slab-out-of-bounds read. Similarly, a 2-byte write overreads by 1 byte. Thus, read only the number of bytes requested using get_unaligned_le16() and get_unaligned_le32() for the 2 and 4 byte cases, interpreting the buffer as little-endian to match the byte ordering of PCI I/O port space. The PowerPC implementation previously compensated for the generic code's native-endian 32-bit load by shifting the value into place for the 1 and 2 byte cases. The shifts were only correct on big-endian kernels. On little-endian PowerPC (POWER8 and later), they extracted the wrong bytes, so a 1-byte write wrote an out-of-bounds byte instead of the requested value. On big-endian, the native load also caused out_le16() and out_le32() to reverse the user's bytes on the wire for 2 and 4 byte writes. The little-endian helpers resolve both issues, so the shifts are removed. No changes are needed for the Alpha platform. The legacy_io file is root-only and exists only on Alpha and PowerPC, the two architectures that define HAVE_PCI_LEGACY. |
Risk And Classification
EPSS: 0.001980000 probability, percentile 0.096920000 (date 2026-09-14)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 e892f05f1f790d5721cd8e3c561ed76da7e08bae git | Not specified |
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 7a99e9c7011905734cc2739038f2a224b6be0d1f git | Not specified |
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 dc76258d0132df1d831a5a29758bd448ca9c566e git | Not specified |
| CNA | Linux | Linux | affected 2.6.12 | Not specified |
| CNA | Linux | Linux | unaffected 2.6.12 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.50 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2.4 7.2.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.3-rc1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/7a99e9c7011905734cc2739038f2a224b6be0d1f | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/dc76258d0132df1d831a5a29758bd448ca9c566e | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/e892f05f1f790d5721cd8e3c561ed76da7e08bae | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.