From: Eduard Zingerman <eddyz87@gmail.com>
To: Brahmajit Das <listout@listout.xyz>
Cc: syzbot+d36d5ae81e1b0a53ef58@syzkaller.appspotmail.com,
andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, haoluo@google.com,
john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org,
linux-kernel@vger.kernel.org, martin.lau@linux.dev,
sdf@fomichev.me, song@kernel.org,
syzkaller-bugs@googlegroups.com, yonghong.song@linux.dev,
kafai.wan@linux.dev
Subject: Re: [PATCH v3 1/2] bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer
Date: Wed, 01 Oct 2025 11:54:01 -0700 [thread overview]
Message-ID: <3b9a4aae9265fd8cc9a7c9576b8b1c54cd2933d1.camel@gmail.com> (raw)
In-Reply-To: <zq2pmlsmmduelzniwez7hnwygx5vl2byrvtvjfabpjtvrwjcxl@eej2larvujkk>
On Thu, 2025-10-02 at 00:19 +0530, Brahmajit Das wrote:
> On 01.10.2025 11:29, Eduard Zingerman wrote:
> > On Wed, 2025-10-01 at 15:26 +0530, Brahmajit Das wrote:
> > > In check_alu_op(), the verifier currently calls check_reg_arg() and
> > > adjust_scalar_min_max_vals() unconditionally for BPF_NEG operations.
> > > However, if the destination register holds a pointer, these scalar
> > > adjustments are unnecessary and potentially incorrect.
> > >
> > > This patch adds a check to skip the adjustment logic when the destination
> > > register contains a pointer.
> > >
> > > Reported-by: syzbot+d36d5ae81e1b0a53ef58@syzkaller.appspotmail.com
> > > Closes: https://syzkaller.appspot.com/bug?extid=d36d5ae81e1b0a53ef58
> > > Fixes: aced132599b3 ("bpf: Add range tracking for BPF_NEG")
> > > Suggested-by: KaFai Wan <kafai.wan@linux.dev>
> > > Signed-off-by: Brahmajit Das <listout@listout.xyz>
> > > ---
> >
> > Acked-by: Eduard Zingerman <eddyz87@gmail.com>
> >
> Thanks
> >
> > Nit: I'd made this a bit simpler: `regs[insn->dst_reg].type == SCALAR_VALUE`,
> > instead of __is_pointer_value() call.
> >
> > > err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
> > > err = err ?: adjust_scalar_min_max_vals(env, insn,
> > > ®s[insn->dst_reg],
> Do I need to send a v4?
As you see fit.
If you agree with my suggestion, please send v4,
leaving it as-is also fine by me.
next prev parent reply other threads:[~2025-10-01 18:54 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-23 9:02 [syzbot] [bpf?] general protection fault in print_reg_state syzbot
2025-09-23 16:41 ` [PATCH 1/1] bpf: fix NULL pointer dereference in print_reg_state() Brahmajit Das
2025-10-01 19:17 ` [PATCH v4 0/2] bpf: Fix verifier crash on BPF_NEG with pointer register Brahmajit Das
2025-10-01 19:17 ` [PATCH v4 1/2] bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer Brahmajit Das
2025-10-01 19:32 ` Eduard Zingerman
2025-10-01 19:17 ` [PATCH v4 2/2] selftests/bpf: Add test for BPF_NEG alu on CONST_PTR_TO_MAP Brahmajit Das
2025-10-01 19:33 ` Eduard Zingerman
2025-10-01 21:10 ` [PATCH v4 0/2] bpf: Fix verifier crash on BPF_NEG with pointer register patchwork-bot+netdevbpf
2025-09-23 16:43 ` [PATCH 1/1] bpf: fix NULL pointer dereference in print_reg_state() Brahmajit Das
2025-09-23 18:52 ` Alexei Starovoitov
2025-09-23 17:10 ` Forwarded: [PATCH] " syzbot
2025-09-23 17:47 ` [PATCH v2] " Brahmajit Das
2025-09-24 7:32 ` Alexei Starovoitov
2025-09-24 9:09 ` Brahmajit Das
2025-09-24 15:40 ` Brahmajit Das
2025-09-24 17:28 ` Alexei Starovoitov
2025-09-24 17:38 ` KaFai Wan
2025-09-24 18:28 ` Brahmajit Das
2025-09-25 15:31 ` KaFai Wan
2025-09-26 1:04 ` Brahmajit Das
2025-09-26 1:56 ` Brahmajit Das
2025-09-26 10:36 ` KaFai Wan
2025-09-30 18:21 ` Brahmajit Das
2025-10-01 5:08 ` KaFai Wan
2025-09-29 18:23 ` [syzbot] [bpf?] general protection fault in print_reg_state syzbot
2025-10-01 9:56 ` [PATCH v3 0/2] bpf: Fix verifier crash on BPF_NEG with pointer register Brahmajit Das
2025-10-01 9:56 ` [PATCH v3 1/2] bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer Brahmajit Das
2025-10-01 16:55 ` Alexei Starovoitov
2025-10-01 18:29 ` Eduard Zingerman
2025-10-01 18:49 ` Brahmajit Das
2025-10-01 18:54 ` Eduard Zingerman [this message]
2025-10-01 9:56 ` [PATCH v3 2/2] selftests/bpf: Add test for BPF_NEG alu on CONST_PTR_TO_MAP Brahmajit Das
2025-10-01 18:37 ` Eduard Zingerman
2025-10-01 18:40 ` [PATCH v3 0/2] bpf: Fix verifier crash on BPF_NEG with pointer register Eduard Zingerman
2025-10-01 19:28 ` [PATCH v4 " Brahmajit Das
2025-10-01 19:28 ` [PATCH v4 1/2] bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer Brahmajit Das
2025-10-01 21:10 ` patchwork-bot+netdevbpf
2025-10-01 19:28 ` [PATCH v4 2/2] selftests/bpf: Add test for BPF_NEG alu on CONST_PTR_TO_MAP Brahmajit Das
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