Hi,
These backports harden BPF JIT against spectre-v2 class of attacks. Without
a predictor flush, execution of new BPF program may use stale prediction
left behind by the freed one.
To avoid this, issue an IBPB flush on all CPUs on JIT program allocation.
The flush is conditional to spectre-v2 mitigation applied.
Patch 1-2: Adds the predictor flush hook and enables it on x86 via IBPB.
bpf: Support for hardening against JIT spraying
x86/bugs: Enable IBPB flush on BPF JIT allocation
Patch 3-6: Narrow the flush to only unprivileged JIT allocations
to avoid redundant flushes. Also adds pack-selection changes
that minimizes flushes.
bpf: Restrict JIT predictor flush to cBPF
bpf: Skip redundant IBPB in pack allocator
bpf: Prefer packs that won't trigger an IBPB flush on allocation
bpf: Prefer dirty packs for eBPF allocations
Patches 1 & 2 had minor header conflicts. Patch 3 had a few conflicts in
bpf_int_jit_compile(), majorly loongarch bpf_int_jit_compile() doesn't use
pack allocator, dropped was_classic hunk.
x86 builds and boots fine in a VM. I don't have build infra for other
arches, relying on the bots for the builds.
---
Pawan Gupta (6):
bpf: Support for hardening against JIT spraying
x86/bugs: Enable IBPB flush on BPF JIT allocation
bpf: Restrict JIT predictor flush to cBPF
bpf: Skip redundant IBPB in pack allocator
bpf: Prefer packs that won't trigger an IBPB flush on allocation
bpf: Prefer dirty packs for eBPF allocations
arch/arm64/net/bpf_jit_comp.c | 4 +--
arch/loongarch/net/bpf_jit.c | 2 +-
arch/powerpc/net/bpf_jit_comp.c | 4 +--
arch/riscv/net/bpf_jit_comp64.c | 2 +-
arch/riscv/net/bpf_jit_core.c | 3 +-
arch/x86/include/asm/nospec-branch.h | 4 +++
arch/x86/kernel/cpu/bugs.c | 50 +++++++++++++++++++++++---
arch/x86/net/bpf_jit_comp.c | 5 +--
include/linux/filter.h | 15 ++++++--
kernel/bpf/core.c | 68 ++++++++++++++++++++++++++++++++----
kernel/bpf/dispatcher.c | 2 +-
11 files changed, 136 insertions(+), 23 deletions(-)
---
base-commit: e46dc0adfe39724bcf52cea47b8f9c9aed86a394
change-id: 20260713-cbpf-jit-spray-hardening-6-18-y-a028879c779c
Best regards,
--
Pawan
