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authorToke Høiland-Jørgensen <toke@redhat.com>2020-09-29 14:45:52 +0200
committerAlexei Starovoitov <ast@kernel.org>2020-09-29 13:09:24 -0700
commit43bc2874e779c17932c447bb06ef4d5188578bdd (patch)
tree7601ec9c820b816b0e332f393946df45a89e262e /kernel/bpf
parent4a1e7c0c63e02daad751842b7880f9bbcdfb6e89 (diff)
bpf: Fix context type resolving for extension programs
Eelco reported we can't properly access arguments if the tracing program is attached to extension program. Having following program: SEC("classifier/test_pkt_md_access") int test_pkt_md_access(struct __sk_buff *skb) with its extension: SEC("freplace/test_pkt_md_access") int test_pkt_md_access_new(struct __sk_buff *skb) and tracing that extension with: SEC("fentry/test_pkt_md_access_new") int BPF_PROG(fentry, struct sk_buff *skb) It's not possible to access skb argument in the fentry program, with following error from verifier: ; int BPF_PROG(fentry, struct sk_buff *skb) 0: (79) r1 = *(u64 *)(r1 +0) invalid bpf_context access off=0 size=8 The problem is that btf_ctx_access gets the context type for the traced program, which is in this case the extension. But when we trace extension program, we want to get the context type of the program that the extension is attached to, so we can access the argument properly in the trace program. This version of the patch is tweaked slightly from Jiri's original one, since the refactoring in the previous patches means we have to get the target prog type from the new variable in prog->aux instead of directly from the target prog. Reported-by: Eelco Chaudron <echaudro@redhat.com> Suggested-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/160138355278.48470.17057040257274725638.stgit@toke.dk
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/btf.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 05816471bac6..4d0ee7839fdb 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4582,7 +4582,14 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
info->reg_type = PTR_TO_BTF_ID;
if (tgt_prog) {
- ret = btf_translate_to_vmlinux(log, btf, t, tgt_prog->type, arg);
+ enum bpf_prog_type tgt_type;
+
+ if (tgt_prog->type == BPF_PROG_TYPE_EXT)
+ tgt_type = tgt_prog->aux->saved_dst_prog_type;
+ else
+ tgt_type = tgt_prog->type;
+
+ ret = btf_translate_to_vmlinux(log, btf, t, tgt_type, arg);
if (ret > 0) {
info->btf_id = ret;
return true;