[PATCH 4.19 03/11] bpf: Inherit expanded/patched seen count from old aux data

Greg Kroah-Hartman
2021-08-13T15:14:11Z

From: Daniel Borkmann <daniel@iogearbox.net>

commit d203b0fd863a2261e5d00b97f3d060c4c2a6db71 upstream.

Instead of relying on current env->pass_cnt, use the seen count from the
old aux data in adjust_insn_aux_data(), and expand it to the new range of
patched instructions. This change is valid given we always expand 1:n
with n>=1, so what applies to the old/original instruction needs to apply
for the replacement as well.

Not relying on env->pass_cnt is a prerequisite for a later change where we
want to avoid marking an instruction seen when verified under speculative
execution path.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Benedict Schlueter <benedict.schlueter@rub.de>
Reviewed-by: Piotr Krysiuk <piotras@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
[OP: - declare old_data as bool instead of u32 (struct bpf_insn_aux_data.seen
is bool in 5.4)
- adjusted context for 4.19]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/verifier.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5690,6 +5690,7 @@ static int adjust_insn_aux_data(struct b
u32 off, u32 cnt)
{
struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
+ bool old_seen = old_data[off].seen;
int i;

if (cnt == 1)
@@ -5701,8 +5702,10 @@ static int adjust_insn_aux_data(struct b
memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
memcpy(new_data + off + cnt - 1, old_data + off,
sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
- for (i = off; i < off + cnt - 1; i++)
- new_data[i].seen = true;
+ for (i = off; i < off + cnt - 1; i++) {
+ /* Expand insni[off]'s seen count to the patched range. */
+ new_data[i].seen = old_seen;
+ }
env->insn_aux_data = new_data;
vfree(old_data);
return 0;