CVE-2022-49840

/// Technical 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

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References