mm/damon/core: handle region split failure in apply_min_nr_regions()

Summary

In the Linux kernel, the following vulnerability has been resolved: mm/damon/core: handle region split failure in apply_min_nr_regions() damon_apply_min_nr_regions() repeatedly split each region until its size becomes small enough to meet the user-defined low limit of the number of regions. The loop assumes the split operation (damon_split_region_at()) will always succeed and create the new region. But the operation could silently fail for memory allocation failures, for example. If such failure happens and the region was the last region, the linked list-based next region fetching returns invalid pointer. As a result, invalid memory dereference and corruption could happen. Even if the corner case is handled, it imposes stress to the allocator by trying split regions for other targets. Fix the issue by breaking all the loops for any region split failure. This means there could be a min_nr_regions violation. It will only rarely happen since the allocation is arguably too small to fail. Even if it happens, it is only temporal. damon_apply_min_nr_regions() will be called again after the aggregation interval. The user impact of the issue should be minor, since the allocation is arguably too small to fail. But, it could still theoretically happen, and the consequence is very bad. This issue was discovered [1] by Sashiko.

Timeline

1. Sep 16, 2026, 10:33 AM UTCCVE published
2. Oct 19, 2026, 8:56 AM UTCRecord last updated

Affected versions

• Linux Linux

  From b1029f29eb1d5fbf07fa8db9b5e7ab6d9813ad67 · fixed in 463ebd63e8ee3d73022a18915ea43320dad8aad7; From b1029f29eb1d5fbf07fa8db9b5e7ab6d9813ad67 · fixed in c608748607620f331196ed0ba9fe4017892c1457

• Linux Linux

  7.1

• KernelLinux

  From 7.1.0 · fixed in 7.2.5

References 2