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 01/10] bpf: mark a NULL call argument precise
Date: Fri, 4 Sep 2026 17:05:52 -0700 [thread overview]
Message-ID: <20260904-register-is-null-precise-fixes-v1-1-0f5a360ff15d@gmail.com> (raw)
In-Reply-To: <20260904-register-is-null-precise-fixes-v1-0-0f5a360ff15d@gmail.com>
check_func_arg() 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.
check_helper_call() enforces second parameter of the
bpf_get_local_storage() to be zero, w/o marking the underlying scalar
register precise. Hence a checkpoint created on such a path would
prune against arbitrary scalar value.
Grouping these two into one patch, as they share the same fixes tag.
Fixes: b5dc0163d8fd ("bpf: precise scalar_value tracking")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
kernel/bpf/verifier.c | 9 ++++++++-
.../testing/selftests/bpf/progs/verifier_subprog_precision.c | 12 ++++++------
2 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9c6ad157a61e..ca362a7ea58c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8752,11 +8752,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
return err;
}
- if (bpf_register_is_null(reg) && type_may_be_null(arg_type))
+ if (bpf_register_is_null(reg) && type_may_be_null(arg_type)) {
/* A NULL register has a SCALAR_VALUE type, so skip
* type checking.
*/
+ err = mark_chain_precision(env, regno);
+ if (err)
+ return err;
goto skip_type_check;
+ }
/* arg_btf_id and arg_size are in a union. */
if (base_type(arg_type) == ARG_PTR_TO_BTF_ID ||
@@ -10906,6 +10910,9 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
verbose(env, "get_local_storage() doesn't support non-zero flags\n");
return -EINVAL;
}
+ err = mark_chain_precision(env, BPF_REG_2);
+ if (err)
+ return err;
break;
case BPF_FUNC_for_each_map_elem:
err = push_callback_call(env, insn, insn_idx, meta.subprogno,
diff --git a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
index e174a905c562..dc0c7034c04f 100644
--- a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
+++ b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
@@ -287,9 +287,9 @@ __msg("17: (b7) r0 = 0")
__msg("18: (95) exit")
__msg("returning from callee:")
__msg("to caller at 9:")
-__msg("frame 0: propagating r1,r4")
+__msg("frame 0: propagating r1,r3,r4")
__msg("mark_precise: frame0: last_idx 9 first_idx 9 subseq_idx -1")
-__msg("mark_precise: frame0: regs=r1,r4 stack= before 18: (95) exit")
+__msg("mark_precise: frame0: regs=r1,r3,r4 stack= before 18: (95) exit")
__msg("from 18 to 9: safe")
__naked int callback_result_precise(void)
{
@@ -419,9 +419,9 @@ __msg("to caller at 9:")
/* r1, r4 are always precise for bpf_loop(),
* r6 was marked before backtracking to callback body.
*/
-__msg("frame 0: propagating r1,r4,r6")
+__msg("frame 0: propagating r1,r3,r4,r6")
__msg("mark_precise: frame0: last_idx 9 first_idx 9 subseq_idx -1")
-__msg("mark_precise: frame0: regs=r1,r4,r6 stack= before 16: (95) exit")
+__msg("mark_precise: frame0: regs=r1,r3,r4,r6 stack= before 16: (95) exit")
__msg("mark_precise: frame1: regs= stack= before 15: (b7) r0 = 0")
__msg("mark_precise: frame1: regs= stack= before 9: (85) call bpf_loop")
__msg("mark_precise: frame0: parent state regs= stack=:")
@@ -575,9 +575,9 @@ __msg("to caller at 10:")
/* r1, r4 are always precise for bpf_loop(),
* fp-8 was marked before backtracking to callback body.
*/
-__msg("frame 0: propagating r1,r4,fp-8")
+__msg("frame 0: propagating r1,r3,r4,fp-8")
__msg("mark_precise: frame0: last_idx 10 first_idx 10 subseq_idx -1")
-__msg("mark_precise: frame0: regs=r1,r4 stack=-8 before 18: (95) exit")
+__msg("mark_precise: frame0: regs=r1,r3,r4 stack=-8 before 18: (95) exit")
__msg("mark_precise: frame1: regs= stack= before 17: (b7) r0 = 0")
__msg("mark_precise: frame1: regs= stack= before 10: (85) call bpf_loop#181")
__msg("mark_precise: frame0: parent state regs= stack=:")
--
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 ` Eduard Zingerman [this message]
2026-09-05 0:21 ` [PATCH bpf 01/10] bpf: mark a NULL call argument precise 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 ` [PATCH bpf 03/10] bpf: mark a NULL memory argument of a call precise Eduard Zingerman
2026-09-05 0:23 ` 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260904-register-is-null-precise-fixes-v1-1-0f5a360ff15d@gmail.com \
--to=eddyz87@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=kernel-team@fb.com \
--cc=martin.lau@linux.dev \
--cc=memxor@gmail.com \
--cc=yonghong.song@linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.