HIGH Introduced in 7.1
dax DirectAccess OOB
CVE-2026-93074
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
KernelScan AI7.8HIGH
01Description
In the Linux kernel, the following vulnerability has been resolved: dax/fsdev: use __va(phys) for kaddr in direct_access Use __va(phys) instead of virt_addr + linear_offset for the kaddr return in __fsdev_dax_direct_access(). The previous code added a device-linear byte offset to virt_addr (which is __va of ranges[0]), but for multi-range devices with physical gaps between ranges, this linear arithmetic crosses the gap and produces a wrong kernel virtual address. Using __va(phys) where phys comes from dax_pgoff_to_phys() is correct for any range layout because the direct map translates each physical address independently. This leaves dev_dax->virt_addr write-only, so remove the field (suggested by Dave Jiang).
02KernelScan AI Analysis
Risk summary
A miscalculated kernel virtual address in the DAX filesystem direct-access path causes file reads and writes on multi-range DAX devices to target the wrong memory location, enabling kernel memory disclosure and corruption. Any user with file access to a DAX-mounted filesystem on affected hardware can trigger the bug. Systems without multi-range DAX devices are not affected.
Vulnerability analysis
When a filesystem uses DAX direct access on a device that has multiple physical memory ranges with gaps between them, the kernel computes the target virtual address by adding a linear byte offset to the base address of the first range. This linear arithmetic ignores the physical gaps, so accesses that span into a second range land at a wrong kernel virtual address—reading or writing memory that does not correspond to the intended file data. The fix replaces the linear calculation with a per-page physical-to-virtual translation that correctly handles any range layout, and removes the now-unnecessary cached base address. The vulnerable path is reachable by any local user who can read or write files on a DAX-mounted filesystem, but it requires specific hardware (a multi-range DAX/NVDIMM device) and root-configured DAX mounting to be present.
Lifecycle
03Fix Versions
| Branch | Introduced | Fixed in | Patch commit |
|---|---|---|---|
| mainline | 7.1 | 7.3-rc1 | ff7c73fca793 |
| 7.2 | 7.1 | 7.2.6 | 7b642bd3d391 |