In the Linux kernel, the following vulnerability has been resolved: iommu/amd: Fix undefined...

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

iommu/amd: Fix undefined behavior in devid_write debugfs function

When for_each_pci_segment() loop completes without finding a matching segment, the pci_seg pointer is not NULL but points to an invalid memory location (the list head). Accessing pci_seg->id after the loop causes undefined behavior.

Fix this by handling the successful case inside the loop and returning -EINVAL after the loop if no matching segment is found.