bpf: Account for insn->off when doing bpf_probe_read_kernel
In the bpf interpreter mode, bpf_probe_read_kernel is used to read
from PTR_TO_BTF_ID's kernel object. It currently missed considering
the insn->off. This patch fixes it.
Fixes: 2a02759ef5f8 ("bpf: Add support for BTF pointers to interpreter")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191107014640.384083-1-kafai@fb.com
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 97e37d8..c1fde03 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1569,7 +1569,7 @@ static u64 __no_fgcse ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u6
#undef LDST
#define LDX_PROBE(SIZEOP, SIZE) \
LDX_PROBE_MEM_##SIZEOP: \
- bpf_probe_read_kernel(&DST, SIZE, (const void *)(long) SRC); \
+ bpf_probe_read_kernel(&DST, SIZE, (const void *)(long) (SRC + insn->off)); \
CONT;
LDX_PROBE(B, 1)
LDX_PROBE(H, 2)