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To: Eric Biggers Cc: Marco Elver , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668692827; a=rsa-sha256; cv=none; b=33lKDDVaihTiRA/Z4lYfv1okSWg5p89w7VkTXRv1/pvc8W/bwOD+VWz+sjMoFoQLQf9Fto maudsaDCCajLzAyeN1VNl+7C2MFRT3kxMRv79wgjsWu3ruiZFOwUB5YA6BJdwBWVKVm+KP 0CNVZJ4hY/2OoLLwNRTK3BaUDSdJC0o= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b="c8vO+LU/"; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf30.hostedemail.com: domain of glider@google.com designates 209.85.219.172 as permitted sender) smtp.mailfrom=glider@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668692827; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=NBgn5FfavxoeQ10DPy6H31rWSKaucrVJq2p8zFcWxKg=; b=T0AqyuwdlDUNTs8jUwthAjrlXDTzQ+oQKjTV/V4oYF2MhYh76LgqT4QipXKHy0va+P6k9J 4tEASsxjqUL2FJ2AmXbQpl4mvYCA313bCRcYO15Oy9E/hDsAuitvl8TUZfbI2RUNu8XZac moi+ZLpD3bPR8diYiU/MX4c9F+JggGw= X-Stat-Signature: rbs6ef8caqy9igtq4uiyzd6otxe3h3o8 X-Rspamd-Queue-Id: E40CD8000E Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b="c8vO+LU/"; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf30.hostedemail.com: domain of glider@google.com designates 209.85.219.172 as permitted sender) smtp.mailfrom=glider@google.com X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1668692827-908272 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Nov 16, 2022 at 9:12 PM Eric Biggers wrote: > > Hi, > > I'm trying v6.1-rc5 with CONFIG_KMSAN, but the kernel continuously spams > "BUG: KMSAN: uninit-value in __init_waitqueue_head". > > I tracked it down to lockdep (CONFIG_PROVE_LOCKING=3Dy). The problem goe= s away if > I disable that. > > I don't see any obvious use of uninitialized memory in __init_waitqueue_h= ead(). > > The compiler I'm using is tip-of-tree clang (LLVM commit 4155be339ba80fef= ). > > Is this a known issue? > > - Eric Thanks for flagging this! The reason behind that is that under lockdep we're accessing the contents of wq_head->lock->dep_map, which KMSAN considers uninitialized. The initialization of dep_map happens inside kernel/locking/lockdep.c, for which KMSAN is deliberately disabled, because lockep used to deadlock in the past. As far as I can tell, removing `KMSAN_SANITIZE_lockdep.o :=3D n` does not actually break anything now (although the kernel becomes quite slow with both lockdep and KMSAN). Let me experiment a bit and send a patch. If this won't work out, we'll need an explicit call to kmsan_unpoison_memory() somewhere in lockdep_init_map_type() to suppress these reports. -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Stra=C3=9Fe, 33 80636 M=C3=BCnchen Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg