From: "Emil Tsalapatis" <emil@etsalapatis.com>
To: "Amery Hung" <ameryhung@gmail.com>,
"Alexei Starovoitov" <alexei.starovoitov@gmail.com>
Cc: "Emil Tsalapatis" <emil@etsalapatis.com>, <bpf@vger.kernel.org>,
<ast@kernel.org>, <andrii@kernel.org>, <eddyz87@gmail.com>,
<memxor@gmail.com>, <daniel@iogearbox.net>,
<netdev@vger.kernel.org>
Subject: Re: [PATCH bpf v2 09/11] bpf: Track whether dynptr type is known
Date: Tue, 22 Sep 2026 20:28:09 +0000 [thread overview]
Message-ID: <DLM4N2XSQ4LE.23XSEE8I96EK9@etsalapatis.com> (raw)
In-Reply-To: <CAMB2axPbLQhGq-LRLzW4p27YVMowcv0XLdF6gNrLn8U3mG_fJA@mail.gmail.com>
On Tue Sep 22, 2026 at 8:23 PM UTC, Amery Hung wrote:
> On Tue, Sep 22, 2026 at 11:49 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
>>
>> On Tue Sep 22, 2026 at 5:20 PM UTC, Emil Tsalapatis wrote:
>> > The TYPE_LOCAL dynptr type is used for two different
>> > kinds of dynptrs in the codebase: Those that are created
>> > locally and backed with a memory region, and those that
>> > are passed as arguments to a global subprog, whose type
>> > is not known at verification time. The two kinds require
>> > different handling in certain scenarios, e.g., packet
>> > pointer invalidation. However, there is no current way
>> > to distinguish them.
>> >
>> > Add a new field, type_unknown, to bpf_reg_state's dynptr-
>> > specific state. The field designates whether the dynptr
>> > type reported is accurate, or a placeholder for "type
>> > unknown". Adding an extra field to bpf_reg_state avoids
>> > unnecessarily splitting TYPE_LOCAL into two types, since
>> > they would behave identically in most cases.
>> >
>> > The change is currently non-functional. The new field is
>> > first used in the next commit.
>> >
>> > Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
>> > ---
>> > include/linux/bpf_verifier.h | 2 ++
>> > kernel/bpf/states.c | 1 +
>> > kernel/bpf/verifier.c | 27 ++++++++++++++++++---------
>> > 3 files changed, 21 insertions(+), 9 deletions(-)
>> >
>> > diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
>> > index be0ccad15..f57730d1d 100644
>> > --- a/include/linux/bpf_verifier.h
>> > +++ b/include/linux/bpf_verifier.h
>> > @@ -71,6 +71,7 @@ struct bpf_reg_state {
>> > /* For dynptr stack slots */
>> > struct {
>> > enum bpf_dynptr_type type;
>> > + bool type_unknown;
>>
>> why extra bool? Can it be another value in enum?
>
> Second this. Could be a BPF_DYNPTR_TYPE_UNKNOWN or BPF_DYNPTR_TYPE_ANY.
Sounds good, let's go with that. The reasoning behind the extra bool was to
avoid having to add TYPE_UNKNOWN everywhere as an extra case statement, because
the two enums would have identical behavior except for the check added in the
next patch.
>
>>
>>
next prev parent reply other threads:[~2026-09-22 20:28 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-22 17:20 [PATCH bpf v2 00/11] skb/arena bugfixes Emil Tsalapatis
2026-09-22 17:20 ` [PATCH bpf v2 01/11] bpf: Fix bounds check for skb-backed dynptrs Emil Tsalapatis
2026-09-22 17:27 ` sashiko-bot
2026-09-22 20:15 ` Amery Hung
2026-09-22 17:20 ` [PATCH bpf v2 02/11] selftests/bpf: Test dynptr slices past end of skb Emil Tsalapatis
2026-09-22 17:28 ` sashiko-bot
2026-09-22 20:16 ` Amery Hung
2026-09-22 17:20 ` [PATCH bpf v2 03/11] bpf: Fix bpf_sock context code generation Emil Tsalapatis
2026-09-22 17:20 ` [PATCH bpf v2 04/11] selftests/bpf: Add selftests for rx_queue_mapping context access Emil Tsalapatis
2026-09-22 17:36 ` sashiko-bot
2026-09-22 17:20 ` [PATCH bpf v2 05/11] bpf: Reject pkt arguments in mutating subprogs Emil Tsalapatis
2026-09-22 20:32 ` Amery Hung
2026-09-22 17:20 ` [PATCH bpf v2 06/11] selftests/bpf: Test rejection of pkt args to " Emil Tsalapatis
2026-09-22 17:20 ` [PATCH bpf v2 07/11] bpf: Prevent variable arena/non-arena register contents Emil Tsalapatis
2026-09-22 17:20 ` [PATCH bpf v2 08/11] selftests/bpf: Test for mixed arena/nonarena code paths Emil Tsalapatis
2026-09-22 17:20 ` [PATCH bpf v2 09/11] bpf: Track whether dynptr type is known Emil Tsalapatis
2026-09-22 18:46 ` Alexei Starovoitov
2026-09-22 20:23 ` Amery Hung
2026-09-22 20:28 ` Emil Tsalapatis [this message]
2026-09-22 17:20 ` [PATCH bpf v2 10/11] bpf: Track skb memory invalidation by packet-backed dynptrs Emil Tsalapatis
2026-09-22 20:06 ` Amery Hung
2026-09-22 20:29 ` Emil Tsalapatis
2026-09-22 17:20 ` [PATCH bpf v2 11/11] selftests/bpf: Test dynptr slice invalidation on skb clobber Emil Tsalapatis
2026-09-22 19:40 ` [PATCH bpf v2 00/11] skb/arena bugfixes patchwork-bot+netdevbpf
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