linux-kernel - [PATCH 5.12 115/178] bpf: Inherit expanded/patched seen count from old aux data

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Message-Id: <20210621154926.689776828@linuxfoundation.org>
Date:   Mon, 21 Jun 2021 18:15:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Benedict Schlueter <benedict.schlueter@....de>,
        Piotr Krysiuk <piotras@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 115/178] bpf: Inherit expanded/patched seen count from old aux data

From: Daniel Borkmann <daniel@...earbox.net>

[ Upstream commit d203b0fd863a2261e5d00b97f3d060c4c2a6db71 ]

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@...earbox.net>
Reviewed-by: John Fastabend <john.fastabend@...il.com>
Reviewed-by: Benedict Schlueter <benedict.schlueter@....de>
Reviewed-by: Piotr Krysiuk <piotras@...il.com>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/bpf/verifier.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index bdf4be10c8cc..0ffe85f22887 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10820,6 +10820,7 @@ static int adjust_insn_aux_data(struct bpf_verifier_env *env,
 {
 	struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
 	struct bpf_insn *insn = new_prog->insnsi;
+	u32 old_seen = old_data[off].seen;
 	u32 prog_len;
 	int i;
 
@@ -10840,7 +10841,8 @@ static int adjust_insn_aux_data(struct bpf_verifier_env *env,
 	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 = env->pass_cnt;
+		/* Expand insni[off]'s seen count to the patched range. */
+		new_data[i].seen = old_seen;
 		new_data[i].zext_dst = insn_has_def32(env, insn + i);
 	}
 	env->insn_aux_data = new_data;
-- 
2.30.2