CVE-2025-38427

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 kernels 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_infos 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

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

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