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(Postfix) with ESMTP id 1CBBF2004D; Tue, 12 Mar 2024 23:52:35 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BAC8420040; Tue, 12 Mar 2024 23:52:34 +0000 (GMT) Received: from heavy (unknown [9.171.20.188]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 12 Mar 2024 23:52:34 +0000 (GMT) Date: Wed, 13 Mar 2024 00:52:33 +0100 From: Ilya Leoshkevich To: Changbin Du , elver@google.com Cc: Alexander Potapenko , Andrew Morton , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [BUG] kmsan: instrumentation recursion problems Message-ID: References: <20240308043448.masllzeqwht45d4j@M910t> <20240311093036.44txy57hvhevybsu@M910t> <20240311110223.nzsplk6a6lzxmzqi@M910t> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240311110223.nzsplk6a6lzxmzqi@M910t> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: XMoEI2_KLVggDytKVnGT_gt9PRMt-t9n X-Proofpoint-ORIG-GUID: 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 vWGT1R2b YZZJukZdnHnoAnu+dPZu5DVgVOpzxlZje9w175IydK4pzc2yGNHnA2d8VrOSViYwL8iGSbXdKRIhqCrH40YCicFQ8dJtsOCR/za2nQ9UhBFvjrkaBUx2pwqkl2PfXoVGZZiF5re8oikWCbHDU672KjakS8rivtMWpVqxp/rvyX/xrgrZil3VEMUCnR1CCCiv3wzMRfpwPJA8WrBSCNGrwoflY2mz9H66X3CTnB391wPTX8TiHhup8slKnmvvEUNbyeoPmE+hNeTMpc/0lfz4llmL7qBoqGuE1Ngmb X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Mon, Mar 11, 2024 at 07:02:23PM +0800, Changbin Du wrote: > On Mon, Mar 11, 2024 at 05:30:36PM +0800, Changbin Du wrote: > > On Fri, Mar 08, 2024 at 10:39:15AM +0100, Marco Elver wrote: > > > On Fri, 8 Mar 2024 at 05:36, 'Changbin Du' via kasan-dev > > > wrote: > > > > > > > > Hey, folks, > > > > I found two instrumentation recursion issues on mainline kernel. > > > > > > > > 1. recur on preempt count. > > > > __msan_metadata_ptr_for_load_4() -> kmsan_virt_addr_valid() -> preempt_disable() -> __msan_metadata_ptr_for_load_4() > > > > > > > > 2. recur in lockdep and rcu > > > > __msan_metadata_ptr_for_load_4() -> kmsan_virt_addr_valid() -> pfn_valid() -> rcu_read_lock_sched() -> lock_acquire() -> rcu_is_watching() -> __msan_metadata_ptr_for_load_8() > > > > > > > > > > > > Here is an unofficial fix, I don't know if it will generate false reports. > > > > > > > > $ git show > > > > commit 7f0120b621c1cbb667822b0f7eb89f3c25868509 (HEAD -> master) > > > > Author: Changbin Du > > > > Date: Fri Mar 8 20:21:48 2024 +0800 > > > > > > > > kmsan: fix instrumentation recursions > > > > > > > > Signed-off-by: Changbin Du > > > > > > > > diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile > > > > index 0db4093d17b8..ea925731fa40 100644 > > > > --- a/kernel/locking/Makefile > > > > +++ b/kernel/locking/Makefile > > > > @@ -7,6 +7,7 @@ obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o > > > > > > > > # Avoid recursion lockdep -> sanitizer -> ... -> lockdep. > > > > KCSAN_SANITIZE_lockdep.o := n > > > > +KMSAN_SANITIZE_lockdep.o := n > > > > > > This does not result in false positives? > > > > This does result lots of false positives. > > > I saw a lot of reports but seems not related to this. > > > > [ 2.742743][ T0] BUG: KMSAN: uninit-value in unwind_next_frame+0x3729/0x48a0 > > [ 2.744404][ T0] unwind_next_frame+0x3729/0x48a0 > > [ 2.745623][ T0] arch_stack_walk+0x1d9/0x2a0 > > [ 2.746838][ T0] stack_trace_save+0xb8/0x100 > > [ 2.747928][ T0] set_track_prepare+0x88/0x120 > > [ 2.749095][ T0] __alloc_object+0x602/0xbe0 > > [ 2.750200][ T0] __create_object+0x3f/0x4e0 > > [ 2.751332][ T0] pcpu_alloc+0x1e18/0x2b00 > > [ 2.752401][ T0] mm_init+0x688/0xb20 > > [ 2.753436][ T0] mm_alloc+0xf4/0x180 > > [ 2.754510][ T0] poking_init+0x50/0x500 > > [ 2.755594][ T0] start_kernel+0x3b0/0xbf0 > > [ 2.756724][ T0] __pfx_reserve_bios_regions+0x0/0x10 > > [ 2.758073][ T0] x86_64_start_kernel+0x92/0xa0 > > [ 2.759320][ T0] secondary_startup_64_no_verify+0x176/0x17b > > > Above reports are triggered by KMEMLEAK and KFENCE. > > Now with below fix, I was able to run kmsan kernel with: > CONFIG_DEBUG_KMEMLEAK=n > CONFIG_KFENCE=n > CONFIG_LOCKDEP=n > > KMEMLEAK and KFENCE generate too many false positives in unwinding code. > LOCKDEP still introduces instrumenting recursions. FWIW I see the same issue on s390, and the best I could come up with so far was also disabling lockdep. For KFENCE I have the following [1] though, maybe this will be helpful to you as well? [1] https://patchwork.kernel.org/project/linux-mm/patch/20231213233605.661251-17-iii@linux.ibm.com/ [...]