From: Martin KaFai Lau <kafai@fb.com>
Date: Wed, 6 Nov 2019 17:46:40 -0800
Subject: bpf: Account for insn->off when doing bpf_probe_read_kernel
Patch-mainline: Queued in subsystem maintainer repository
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Git-commit: 85d31dd07002315c0d1816543fdc392c8cc6b73a
References: bsc#1155518

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
Acked-by: Gary Lin <glin@suse.com>
---
 kernel/bpf/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1569,7 +1569,7 @@ out:
 #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)