From: Daniel Borkmann <daniel@iogearbox.net>
Date: Wed, 16 Oct 2024 13:49:12 +0000 (+0200)
Subject: bpf: Fix print_reg_state's constant scalar dump
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3e9e708757ca3b7eb65a820031d62fea1a265709;p=users%2Fhch%2Fmisc.git

bpf: Fix print_reg_state's constant scalar dump

print_reg_state() should not consider adding reg->off to reg->var_off.value
when dumping scalars. Scalars can be produced with reg->off != 0 through
BPF_ADD_CONST, and thus as-is this can skew the register log dump.

Fixes: 98d7ca374ba4 ("bpf: Track delta between "linked" registers.")
Reported-by: Nathaniel Theis <nathaniel.theis@nccgroup.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241016134913.32249-2-daniel@iogearbox.net
---

diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 5aebfc3051e3..4a858fdb6476 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -688,8 +688,7 @@ static void print_reg_state(struct bpf_verifier_env *env,
 	if (t == SCALAR_VALUE && reg->precise)
 		verbose(env, "P");
 	if (t == SCALAR_VALUE && tnum_is_const(reg->var_off)) {
-		/* reg->off should be 0 for SCALAR_VALUE */
-		verbose_snum(env, reg->var_off.value + reg->off);
+		verbose_snum(env, reg->var_off.value);
 		return;
 	}