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[82.192.244.13]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435e10e474csm27831563f8f.2.2026.01.31.01.39.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Jan 2026 01:39:43 -0800 (PST) Sender: Salvatore Bonaccorso Received: by eldamar.lan (Postfix, from userid 1000) id E6ADABE2EE7; Sat, 31 Jan 2026 10:39:42 +0100 (CET) Date: Sat, 31 Jan 2026 10:39:42 +0100 From: Salvatore Bonaccorso To: Peter Zijlstra Cc: mingo@kernel.org, oleg@redhat.com, linux-kernel@vger.kernel.org, debian-kernel@lists.debian.org, Kees Cook Subject: Re: [PATCH] seqlock: Allow UBSAN to fail optimizing Message-ID: Mail-Followup-To: Peter Zijlstra , mingo@kernel.org, oleg@redhat.com, linux-kernel@vger.kernel.org, debian-kernel@lists.debian.org, Kees Cook References: <20260129110733.GA166857@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260129110733.GA166857@noisy.programming.kicks-ass.net> Hi Peter, [Adding Kees as well] On Thu, Jan 29, 2026 at 12:07:33PM +0100, Peter Zijlstra wrote: > > Very similar to commit: > > b94d45b6bbb4 ("seqlock: Allow KASAN to fail optimizing") > > mark UBSAN as failing to optimize and not suitable for release builds. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-kbuild-all/202601290910.uwScjRjc-lkp@intel.com/ > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123873 > Signed-off-by: Peter Zijlstra (Intel) > --- > > Debian folks, can you please remove CONFIG_UBSAN=y from your builds, > this is, per GCC devs, not a feature suitable for production! > > diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h > index c00063dffba3..436f05bf5dd7 100644 > --- a/include/linux/seqlock.h > +++ b/include/linux/seqlock.h > @@ -1259,14 +1259,14 @@ static __always_inline void __scoped_seqlock_cleanup(struct ss_tmp *sst) > > extern void __scoped_seqlock_invalid_target(void); > > -#if (defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 90000) || defined(CONFIG_KASAN) > +#if (defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 90000) || defined(CONFIG_KASAN) || defined(CONFIG_UBSAN) > /* > * For some reason some GCC-8 architectures (nios2, alpha) have trouble > * determining that the ss_done state is impossible in __scoped_seqlock_next() > * below. > * > - * Similarly KASAN is known to confuse compilers enough to break this. But we > - * don't care about code quality for KASAN builds anyway. > + * Similarly *SAN is known to confuse compilers enough to break this. But we > + * don't care about code quality for *SAN builds anyway. > */ > static inline void __scoped_seqlock_bug(void) { } > #else Kees, Peter approached the Debian kernel list above to drop CONFIG_UBSAN again, which, so I think we need to revert your 6cfadabfe015 ("Enable UBSAN_BOUNDS and UBSAN_SHIFT"): https://salsa.debian.org/kernel-team/linux/-/commit/6cfadabfe015fa0d659fc8e3efd495cbcae3e44e I have make a MR for our packaging for the change in https://salsa.debian.org/kernel-team/linux/-/merge_requests/1804 Regards, Salvatore