[PATCH 4.4 62/88] bpf: support 8-byte metafield access

Greg Kroah-Hartman
2018-12-14T12:18:08Z

From: Alexei Starovoitov <ast@fb.com>

commit cedaf52693f02372010548c63b2e63228b959099 upstream.

The verifier supported only 4-byte metafields in
struct __sk_buff and struct xdp_md. The metafields in upcoming
struct bpf_perf_event are 8-byte to match register width in struct pt_regs.
Teach verifier to recognize 8-byte metafield access.
The patch doesn't affect safety of sockets and xdp programs.
They check for 4-byte only ctx access before these conditions are hit.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/verifier.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1844,7 +1844,8 @@ static int do_check(struct verifier_env
if (err)
return err;

- if (BPF_SIZE(insn->code) != BPF_W) {
+ if (BPF_SIZE(insn->code) != BPF_W &&
+ BPF_SIZE(insn->code) != BPF_DW) {
insn_idx++;
continue;
}
@@ -2220,9 +2221,11 @@ static int convert_ctx_accesses(struct v
for (i = 0; i < insn_cnt; i++, insn++) {
u32 cnt;

- if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
+ if (insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
+ insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
type = BPF_READ;
- else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
+ else if (insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
+ insn->code == (BPF_STX | BPF_MEM | BPF_DW))
type = BPF_WRITE;
else
continue;