diff mbox series

[4.19,1/4] bpf: Inherit expanded/patched seen count from old aux data

Message ID 20210812170037.2370387-2-ovidiu.panait@windriver.com
State New
Headers show
Series bpf: backport fixes for CVE-2021-33624 | expand

Commit Message

Ovidiu Panait Aug. 12, 2021, 5 p.m. UTC 
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>
---
 kernel/bpf/verifier.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4ce032c4acd0..70cadee591f3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5690,6 +5690,7 @@  static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len,
 				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 bpf_verifier_env *env, u32 prog_len,
 	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;