[ Upstream commit 87338c8e2cbb317b5f757e6172f94e2e3799cd20 ]
The assumption of unconditionally reloading skb pointers on BPF helper calls where bpf_helper_changes_pkt_data() holds true is wrong. There can be different contexts where the helper would enforce a reload such as in case of XDP. Here, we do have a struct xdp_buff instead of struct sk_buff as context, thus this will access garbage.
JITs only ever need to deal with cached skb pointer reload when ld_abs/ind was seen, therefore guard the reload behind SEEN_SKB.
Fixes: 156d0e290e96 ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF") Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com Acked-by: Alexei Starovoitov ast@kernel.org Tested-by: Sandipan Das sandipan@linux.vnet.ibm.com Signed-off-by: Alexei Starovoitov ast@kernel.org --- arch/powerpc/net/bpf_jit_comp64.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index a66e64b..5d115bd 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -762,7 +762,8 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, func = (u8 *) __bpf_call_base + imm;
/* Save skb pointer if we need to re-cache skb data */ - if (bpf_helper_changes_pkt_data(func)) + if ((ctx->seen & SEEN_SKB) && + bpf_helper_changes_pkt_data(func)) PPC_BPF_STL(3, 1, bpf_jit_stack_local(ctx));
bpf_jit_emit_func_call(image, ctx, (u64)func); @@ -771,7 +772,8 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, PPC_MR(b2p[BPF_REG_0], 3);
/* refresh skb cache */ - if (bpf_helper_changes_pkt_data(func)) { + if ((ctx->seen & SEEN_SKB) && + bpf_helper_changes_pkt_data(func)) { /* reload skb pointer to r3 */ PPC_BPF_LL(3, 1, bpf_jit_stack_local(ctx)); bpf_jit_emit_skb_loads(image, ctx);