| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2025-21851: bpf: Fix softlockup in arena_map_free on 64k page kernel |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2025-21851 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.9 with commit 317460317a02a1af512697e6e964298dedd8a163 and fixed in 6.12.17 with commit c1f3f3892d4526f18aaeffdb6068ce861e793ee3 |
| Issue introduced in 6.9 with commit 317460317a02a1af512697e6e964298dedd8a163 and fixed in 6.13.5 with commit 787d556a3de447e70964a4bdeba9196f62a62b1e |
| Issue introduced in 6.9 with commit 317460317a02a1af512697e6e964298dedd8a163 and fixed in 6.14 with commit 517e8a7835e8cfb398a0aeb0133de50e31cae32b |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2025-21851 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| kernel/bpf/arena.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/c1f3f3892d4526f18aaeffdb6068ce861e793ee3 |
| https://git.kernel.org/stable/c/787d556a3de447e70964a4bdeba9196f62a62b1e |
| https://git.kernel.org/stable/c/517e8a7835e8cfb398a0aeb0133de50e31cae32b |
