From nobody Wed Feb 11 09:19:15 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59C3612DD88 for ; Tue, 30 Jul 2024 11:44:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722339876; cv=none; b=pcfR5TtYFWrR5ZQ/jN77Rp9wiXCujZEGzZLyX6AwNJSMXhmTY3XZegrbfTZtUR1y4Knyu8lPt42BBYhVQXMueAwdYtbJ3t8XGRFmL8GCNdSJohtWFbNxQ2BFCIvSMmCxlyPliJMIsoQejtLf19N51dCuyhRCehSinQM/rhR16pI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722339876; c=relaxed/simple; bh=J6l5W49n9iB+uwt8CQ5AwWNy3Kxlt/FstVprC/06sNs=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=PeCLtNz1M9O6dvU4OEvnJS1JOTR8Zjeu6OyJ7CYS0cmIvpA9kXGOcKx7VV0vk2Vva5r6CAB2ERXwj99J7YrrDoT0ozfYz4HgNNWwO2UL8S9CYISRQtKVx/Vi9mE1cFVlS+e5EHUabhBqwLncgozZHUwVuN4PQk/olxNiJJs75e0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=p7/icNJO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="p7/icNJO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA5FDC32782; Tue, 30 Jul 2024 11:44:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722339875; bh=J6l5W49n9iB+uwt8CQ5AwWNy3Kxlt/FstVprC/06sNs=; h=From:To:Cc:Subject:Date:From; b=p7/icNJOorkHw2oyyid0QdM7u2sShTPcn/oid4wg/yX7l3KOB7qv9gIYedc6s3OEA 5frJ+dO+wtno+AtyLQgO23wT3ofFWtEU2GJ8wHErrr5RL7Y1+TNqvNPGBIkSEt4Xv5 SGbFH1AtHRKhJtXRAtYlkIYD0ZWeO/96aiuV36rYU6lnUGWd372xSjizDALcr7k8ry qOx5VqVxlMgb7QE03nskbeQMf4MWaTIeq9U2e4Y3xIY7bgCYDE+PnMkHTsSXFW7Q1h GlCZU/MBKBqC/puNpPHR6i1+r4plFC9OlHRYHJBi+C+akm57DkU8DPgNO0kHbOK6L5 4M7yVBA5kvPeg== From: Will Deacon To: linux-kernel@vger.kernel.org Cc: Will Deacon , Tejun Heo , Lai Jiangshan Subject: [PATCH] workqueue: Fix UBSAN 'subtraction overflow' error in shift_and_mask() Date: Tue, 30 Jul 2024 12:44:31 +0100 Message-Id: <20240730114431.1119-1-will@kernel.org> X-Mailer: git-send-email 2.20.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" UBSAN reports the following 'subtraction overflow' error when booting in a virtual machine on Android: | Internal error: UBSAN: integer subtraction overflow: 00000000f2005515 [#= 1] PREEMPT SMP | Modules linked in: | CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.10.0-00006-g3cbe9e5abd46-dir= ty #4 | Hardware name: linux,dummy-virt (DT) | pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=3D--) | pc : cancel_delayed_work+0x34/0x44 | lr : cancel_delayed_work+0x2c/0x44 | sp : ffff80008002ba60 | x29: ffff80008002ba60 x28: 0000000000000000 x27: 0000000000000000 | x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 | x23: 0000000000000000 x22: 0000000000000000 x21: ffff1f65014cd3c0 | x20: ffffc0e84c9d0da0 x19: ffffc0e84cab3558 x18: ffff800080009058 | x17: 00000000247ee1f8 x16: 00000000247ee1f8 x15: 00000000bdcb279d | x14: 0000000000000001 x13: 0000000000000075 x12: 00000a0000000000 | x11: ffff1f6501499018 x10: 00984901651fffff x9 : ffff5e7cc35af000 | x8 : 0000000000000001 x7 : 3d4d455453595342 x6 : 000000004e514553 | x5 : ffff1f6501499265 x4 : ffff1f650ff60b10 x3 : 0000000000000620 | x2 : ffff80008002ba78 x1 : 0000000000000000 x0 : 0000000000000000 | Call trace: | cancel_delayed_work+0x34/0x44 | deferred_probe_extend_timeout+0x20/0x70 | driver_register+0xa8/0x110 | __platform_driver_register+0x28/0x3c | syscon_init+0x24/0x38 | do_one_initcall+0xe4/0x338 | do_initcall_level+0xac/0x178 | do_initcalls+0x5c/0xa0 | do_basic_setup+0x20/0x30 | kernel_init_freeable+0x8c/0xf8 | kernel_init+0x28/0x1b4 | ret_from_fork+0x10/0x20 | Code: f9000fbf 97fffa2f 39400268 37100048 (d42aa2a0) | ---[ end trace 0000000000000000 ]--- | Kernel panic - not syncing: UBSAN: integer subtraction overflow: Fatal e= xception This is due to shift_and_mask() using a signed immediate to construct the mask and being called with a shift of 31 (WORK_OFFQ_POOL_SHIFT) so that it ends up decrementing from INT_MIN. Use an unsigned constant '1U' to generate the mask in shift_and_mask(). Cc: Tejun Heo Cc: Lai Jiangshan Fixes: 1211f3b21c2a ("workqueue: Preserve OFFQ bits in cancel[_sync] paths") Signed-off-by: Will Deacon --- kernel/workqueue.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 1745ca788ede..b35f8ce80bc7 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -897,7 +897,7 @@ static struct worker_pool *get_work_pool(struct work_st= ruct *work) =20 static unsigned long shift_and_mask(unsigned long v, u32 shift, u32 bits) { - return (v >> shift) & ((1 << bits) - 1); + return (v >> shift) & ((1U << bits) - 1); } =20 static void work_offqd_unpack(struct work_offq_data *offqd, unsigned long = data) --=20 2.46.0.rc1.232.g9752f9e123-goog