CVE-2026-89962

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

powerpc/kexec_file: Prevent kexec range truncation

Sashiko AI review pointed out the following issue.

The __merge_memory_ranges() function incorrectly handles overlapping

memory ranges when merging them. Although sort_memory_ranges() sorts all

ranges by their start address in ascending order beforehand, the merge

logic remains defective in two ways:

1. It compares the current range's start against the previous element (i-1)

instead of the running target index (idx)

2. It unconditionally overwrites 'ranges[idx].end' with 'ranges[i].end'.

This logic flaw leads to critical memory truncation when a larger memory

range completely subsumes subsequent smaller ranges.

For example, consider a sorted input array with three ranges:

Range A (idx=0): [0x1000 - 0x9000]

Range B (i=1): [0x2000 - 0x5000] (completely inside Range A)

Range C (i=2): [0x6000 - 0x8000] (completely inside Range A)

1. When i=1 (Range B):

ranges[1].start (0x2000) <= ranges[0].end + 1 (0x9001) is TRUE.

The code executes: ranges[0].end = ranges[1].end, which erroneously

shrinks Range A's end from 0x9000 down to 0x5000.

2. When i=2 (Range C):

ranges[2].start (0x6000) <= ranges[1].end + 1 (0x5001) is FALSE.

The code falls into the else block, creating a broken new range.

As a result, valid memory fragments [0x5001 - 0x5fff] and [0x8001 - 0x9000]

are completely lost from the kexec exclude lists, potentially allowing

the crash kernel to overwrite active memory, causing data corruption

or crashes.

Fix this by ensuring the start of the current range is compared against the

end of the active merged range (idx), and use max() to safely prevent the

outer boundary from being truncated.