From: Eduard Zingerman <eddyz87@gmail.com>
To: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org
Cc: daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com,
yonghong.song@linux.dev, eddyz87@gmail.com, memxor@gmail.com
Subject: [PATCH bpf 03/10] bpf: mark a NULL memory argument of a call precise
Date: Fri, 4 Sep 2026 17:05:54 -0700 [thread overview]
Message-ID: <20260904-register-is-null-precise-fixes-v1-3-0f5a360ff15d@gmail.com> (raw)
In-Reply-To: <20260904-register-is-null-precise-fixes-v1-0-0f5a360ff15d@gmail.com>
check_mem_reg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.
The argument may live on the stack rather than in a register when a
call has more than MAX_BPF_FUNC_REG_ARGS arguments, hence the new
mark_arg_precision() helper.
Fixes: e5069b9c23b3 ("bpf: Support pointers in global func args")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
kernel/bpf/verifier.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ca362a7ea58c..b758f2822754 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4246,6 +4246,15 @@ static int mark_stack_arg_precision(struct bpf_verifier_env *env, int arg_idx)
return mark_chain_precision_batch(env, env->cur_state);
}
+static int mark_arg_precision(struct bpf_verifier_env *env, argno_t argno)
+{
+ int regno = reg_from_argno(argno);
+
+ if (regno >= 0)
+ return mark_chain_precision(env, regno);
+ return mark_stack_arg_precision(env, arg_idx_from_argno(argno));
+}
+
static int check_outgoing_stack_args(struct bpf_verifier_env *env, struct bpf_func_state *caller,
int nargs, const char *callee_name, const struct btf *btf,
const struct btf_param *args)
@@ -7168,7 +7177,7 @@ static int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg
int size, err = 0;
if (bpf_register_is_null(reg))
- return 0;
+ return mark_arg_precision(env, argno);
if (known_memory)
*known_memory = true;
--
2.55.0
next prev parent reply other threads:[~2026-09-05 0:06 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-05 0:05 [PATCH bpf 00/10] bpf: add missing precision propagation after bpf_register_is_null calls Eduard Zingerman
2026-09-05 0:05 ` [PATCH bpf 01/10] bpf: mark a NULL call argument precise Eduard Zingerman
2026-09-05 0:21 ` sashiko-bot
2026-09-05 0:05 ` [PATCH bpf 02/10] selftests/bpf: precision of a NULL helper argument Eduard Zingerman
2026-09-05 0:05 ` Eduard Zingerman [this message]
2026-09-05 0:23 ` [PATCH bpf 03/10] bpf: mark a NULL memory argument of a call precise sashiko-bot
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 0:05 ` [PATCH bpf 04/10] selftests/bpf: precision of a NULL global subprogram memory argument Eduard Zingerman
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 0:05 ` [PATCH bpf 05/10] bpf: mark a NULL kfunc argument precise Eduard Zingerman
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 0:05 ` [PATCH bpf 06/10] selftests/bpf: precision of a NULL kfunc argument Eduard Zingerman
2026-09-05 0:05 ` [PATCH bpf 07/10] bpf: mark a NULL BTF_ID argument of a global subprogram precise Eduard Zingerman
2026-09-05 0:19 ` sashiko-bot
2026-09-05 0:05 ` [PATCH bpf 08/10] selftests/bpf: precision of a NULL global subprogram BTF_ID argument Eduard Zingerman
2026-09-05 0:06 ` [PATCH bpf 09/10] bpf: propagate mark_chain_precision() errors out of loop_flag_is_zero() Eduard Zingerman
2026-09-05 0:06 ` [PATCH bpf 10/10] bpf: use mark_arg_precision() in check_mem_size_reg() Eduard Zingerman
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 1:20 ` [PATCH bpf 00/10] bpf: add missing precision propagation after bpf_register_is_null calls patchwork-bot+netdevbpf
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