CVE-2026-23383

In the Linux kernel, the following vulnerability has been resolved:

bpf, arm64: Force 8-byte alignment for JIT buffer to prevent atomic tearing

struct bpf_plt contains a u64 target field. Currently, the BPF JIT

allocator requests an alignment of 4 bytes (sizeof(u32)) for the JIT

buffer.

Because the base address of the JIT buffer can be 4-byte aligned (e.g.,

ending in 0x4 or 0xc), the relative padding logic in build_plt() fails

to ensure that target lands on an 8-byte boundary.

This leads to two issues:

1. UBSAN reports misaligned-access warnings when dereferencing the

structure.

2. More critically, target is updated concurrently via WRITE_ONCE() in

bpf_arch_text_poke() while the JIT'd code executes ldr. On arm64,

64-bit loads/stores are only guaranteed to be single-copy atomic if

they are 64-bit aligned. A misaligned target risks a torn read,

causing the JIT to jump to a corrupted address.

Fix this by increasing the allocation alignment requirement to 8 bytes

(sizeof(u64)) in bpf_jit_binary_pack_alloc(). This anchors the base of

the JIT buffer to an 8-byte boundary, allowing the relative padding math

in build_plt() to correctly align the target field.