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bpf, ppc64: do not reload skb pointers in non-skb context

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[ Upstream commit 87338c8e2c ]

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: 156d0e290e ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Borkmann
2017-12-22 16:23:02 +01:00
committed by Greg Kroah-Hartman
parent 83ab155d14
commit 8a681dfd8f
1 changed files with 4 additions and 2 deletions
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6
arch/powerpc/net/bpf_jit_comp64.c
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@@ -762,7 +762,8 @@ emit_clear:
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 @@ emit_clear:
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);