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Tue, 25 Mar 2025 13:22:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.42]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id F3ADF195609D; Tue, 25 Mar 2025 13:22:10 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 25 Mar 2025 14:21:41 +0100 (CET) Date: Tue, 25 Mar 2025 14:21:36 +0100 From: Oleg Nesterov To: Mateusz Guzik Cc: syzbot , brauner@kernel.org, kees@kernel.org, viro@zeniv.linux.org.uk, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH] exec: fix the racy usage of fs_struct->in_exec Message-ID: <20250325132136.GB7904@redhat.com> References: <67dc67f0.050a0220.25ae54.001f.GAE@google.com> <20250324160003.GA8878@redhat.com> <20250324182722.GA29185@redhat.com> <20250325100936.GC29185@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Rspamd-Queue-Id: 7D28E140007 X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: 6emd539xbwwmkqrnpf4cx6pxj8gfc4rm X-HE-Tag: 1742908945-159515 X-HE-Meta: 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 +SHvFpVv xijVGOheTHJQAjmuA74HISLdcZzZ0g6oFkC+CJeZrLOcZjEWqEimOU9k63ch0vTnYRJ4y5mlgPUwoZTnesap14ySxA7f2WOOoX5faSJs/f/qNGRZNiyz5HEJO0w8V0CHVTcveZ4uQFvF3I0LEqPoGAxw59kvcDbKjfm7V+q4+fdKsETYxiRLu1YWtpNVs1OkF3Mo/4F6BWWSujd8JwHNNRZmm98Q4jjJvuUme3hiVnQlyPC7cmjPzo8sZ6mlRRw/Xyh4bNaSt43YNt8NX9IEb+Qa0lVpwTEzPAUaDjii7QVD29eUzOZZjh0yVMujRx2KPTU0tVUAI2c+7DRZqOgkVHDb1GFcnrjrMAQO59nxg0CCneSM9DFhQN5txJmozBieIxH72b/nhTsvYf+d67v5m2Yu5EKL9Mi4zhAHr X-Bogosity: Ham, tests=bogofilter, spamicity=0.001788, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/25, Mateusz Guzik wrote: > > On Tue, Mar 25, 2025 at 11:10 AM Oleg Nesterov wrote: > > > > On 03/24, Mateusz Guzik wrote: > > > > > > On Mon, Mar 24, 2025 at 7:28 PM Oleg Nesterov wrote: > > > > > > > > So to me it would be better to have the trivial fix for stable, > > > > exactly because it is trivially backportable. Then cleanup/simplify > > > > this logic on top of it. > > > > > > So I got myself a crap testcase with a CLONE_FS'ed task which can > > > execve and sanity-checked that suid is indeed not honored as expected. > > > > So you mean my patch can't fix the problem? > > No, I think the patch works. > > I am saying the current scheme is avoidably hard to reason about. Ah, OK, thanks. Then I still think it makes more sense to do the cleanups you propose on top of this fix. But I leave this to you and other fs/ maintainers. Oleg.