vulnerability
Red Hat: CVE-2025-21851: kernel: bpf: Fix softlockup in arena_map_free on 64k page kernel (Multiple Advisories)
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 1 | (AV:L/AC:L/Au:M/C:N/I:N/A:P) | Mar 12, 2025 | Jul 9, 2025 | Jan 28, 2026 |
Description
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix softlockup in arena_map_free on 64k page kernel
On an aarch64 kernel with CONFIG_PAGE_SIZE_64KB=y,
arena_htab tests cause a segmentation fault and soft lockup.
The same failure is not observed with 4k pages on aarch64.
It turns out arena_map_free() is calling
apply_to_existing_page_range() with the address returned by
bpf_arena_get_kern_vm_start(). If this address is not page-aligned
the code ends up calling apply_to_pte_range() with that unaligned
address causing soft lockup.
Fix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the
division by 2 in bpf_arena_get_kern_vm_start() returns
a page-aligned value.
Solutions
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