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Mon, 23 Feb 2026 07:16:49 -0800 (PST) Date: Mon, 23 Feb 2026 16:16:44 +0100 From: =?utf-8?Q?G=C3=BCnther?= Noack To: Ding Yihan Cc: =?utf-8?Q?G=C3=BCnther?= Noack , syzbot , =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , linux-security-module@vger.kernel.org, Jann Horn , Paul Moore Subject: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback Message-ID: References: <69995a88.050a0220.340abe.0d25.GAE@google.com> <00A9E53EDC82309F+7b1dfc69-95f8-4ffc-a67c-967de0e2dfee@uniontech.com> <20260221.5d8a306bcaf1@gnoack.org> <20260221.3ff0e30e4010@gnoack.org> <20260223.52c45aed20f8@gnoack.org> <32095877A7CB47CB+bb9e1be8-59c2-46d9-b1ef-f22d2d8c386e@uniontech.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <32095877A7CB47CB+bb9e1be8-59c2-46d9-b1ef-f22d2d8c386e@uniontech.com> Hello! On Mon, Feb 23, 2026 at 07:29:56PM +0800, Ding Yihan wrote: > Thank you for the detailed analysis and the clear breakdown. > Apologies for the delayed response. I spent the last couple of days > thoroughly reading through the previous mailing list discussions. I > was trying hard to see if there was any viable pure lockless design > that could solve this concurrency issue while preserving the original > architecture. >  > However, after looking at the complexities you outlined, I completely > agree with your conclusion: serializing the TSYNC operations is indeed > the most robust and reasonable path forward to prevent the deadlock. >  > Regarding the lock choice, since 'cred_guard_mutex' is explicitly > marked as deprecated for new code in the kernel,maybe we can use its > modern replacement: 'exec_update_lock' (using down_write_trylock / > up_write on current->signal). This aligns with the current subsystem > standards and was also briefly touched upon by Jann in the older > discussions. >  > I fully understand the requirement for the two-part patch series: > 1. Cleaning up the cancellation logic and comments. > 2. Introducing the serialization lock for TSYNC. >  > I will take some time to draft and test this patch series properly. > I also plan to discuss this with my kernel colleagues here at > UnionTech to see if they have any additional suggestions on the > implementation details before I submit it. >  > I will send out the v1 patch series to the list as soon as it is > ready. Thanks again for your guidance and the great discussion! Thank you, Ding, this is much appreciated! I agree, the `exec_update_lock` might be the better solution; I also need to familiarize myself more with it to double-check. —Günther