CVE-2025-38427

Summary

In the Linux kernel, the following vulnerability has been resolved:

video: screen_info: Relocate framebuffers behind PCI bridges

Apply PCI host-bridge window offsets to screen_info framebuffers. Fixes invalid access to I/O memory.

Resources behind a PCI host bridge can be relocated by a certain offset in the kernel's CPU address range used for I/O. The framebuffer memory range stored in screen_info refers to the CPU addresses as seen during boot (where the offset is 0). During boot up, firmware may assign a different memory offset to the PCI host bridge and thereby relocating the framebuffer address of the PCI graphics device as seen by the kernel. The information in screen_info must be updated as well.

The helper pcibios_bus_to_resource() performs the relocation of the screen_info's framebuffer resource (given in PCI bus addresses). The result matches the I/O-memory resource of the PCI graphics device (given in CPU addresses). As before, we store away the information necessary to later update the information in screen_info itself.

Commit 78aa89d1dfba ("firmware/sysfb: Update screen_info for relocated EFI framebuffers") added the code for updating screen_info. It is based on similar functionality that pre-existed in efifb. Efifb uses a pointer to the PCI resource, while the newer code does a memcpy of the region. Hence efifb sees any updates to the PCI resource and avoids the issue.

v3:

• Only use struct pci_bus_region for PCI bus addresses (Bjorn)
• Clarify address semantics in commit messages and comments (Bjorn) v2:
• Fixed tags (Takashi, Ivan)
• Updated information on efifb

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/cc3cc41ed67054a03134bea42408c720eec0fa04
• https://git.kernel.org/stable/c/5c70e3ad85d2890d8af375333699429de26327f2
• https://git.kernel.org/stable/c/aeda386d86d79269a08f470dbdc53d13a91e51fa
• https://git.kernel.org/stable/c/2f29b5c231011b94007d2c8a6d793992f2275db1

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