linux-kernel - Re: [PATCH v4 1/2] bpf: Skip scalar adjustment for BPF

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Message-ID: <8f72a29f419377ac9e3ddd7ae56bc1e0826058c6.camel@gmail.com>
Date: Wed, 01 Oct 2025 12:32:11 -0700
From: Eduard Zingerman <eddyz87@...il.com>
To: Brahmajit Das <listout@...tout.xyz>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 daniel@...earbox.net, 	haoluo@...gle.com, john.fastabend@...il.com,
 jolsa@...nel.org, kpsingh@...nel.org, 	linux-kernel@...r.kernel.org,
 martin.lau@...ux.dev, sdf@...ichev.me, 	song@...nel.org,
 syzbot+d36d5ae81e1b0a53ef58@...kaller.appspotmail.com, 
	syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev, KaFai Wan	
 <kafai.wan@...ux.dev>
Subject: Re: [PATCH v4 1/2] bpf: Skip scalar adjustment for BPF_NEG if dst
 is a pointer

On Thu, 2025-10-02 at 00:47 +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@...kaller.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@...ux.dev>
> Suggested-by: Eduard Zingerman <eddyz87@...il.com>
> Signed-off-by: Brahmajit Das <listout@...tout.xyz>
> ---

Acked-by: Eduard Zingerman <eddyz87@...il.com>

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