From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 83506405C3F; Fri, 4 Sep 2026 06:05:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501901; cv=none; b=TN/Hw6nqNlCKCHxVpUQKvm5T6DLiEBnLvj+qg1QIhYxMbDdxMnhffZkQLvJvIvfENCbVzKt27HcdUHIzwDYTwMkkYpPmgLm9KiOvQcELpymNAWgUy+cBHYQxEGF7l4B6PUpdZo/FA6SvmIGqAbBwWfmuHflF8bh5Ld+4xeuGAHM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501901; c=relaxed/simple; bh=tSqQ1eJBu1U4xQ4auJLd8/PKYzEcsfirjMedk5rTbDU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FNdjb71HDZlf9QD560NDppWQfuBNjkCt0GET15oAwqSEaXSXj9FnEFLiUz1/2VTBWR5uUtLcb4IkgXMI5Vi3q/5lbr7Nt7OyVW2uMEKfHUdFwwaLvk2GJkCniqLRtMYLK1j8VZtt+O1y8xKP+lYdWqF9PeMD0odGSbce6/I/3DA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kndeJ/o8; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kndeJ/o8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D99071F00A3D; Fri, 4 Sep 2026 06:04:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788501900; bh=mpgLxLf4/AbXFyGnwM0d77oQHAfJ1RjWju/aPR76gGk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kndeJ/o8nFtZXMcgRztdqTYUgjnRNcGwdAEC5UjG/42HRbbvcjQw3sdqDc8PWBh6q csb2NfjqJ4YInxQdAmY2f2IM1fGD0EMHj1yahCM9oBuPUXvYf4VBQUA6PYKUSMuFRl Cqj0LrBfTrEdSvYDOai67A+y6lOLC8RDzF5a9v8w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yang Erkun , Yu Kuai , Sasha Levin Subject: [PATCH 6.12 002/403] md: make rdev_addable usable for rcu mode Date: Fri, 4 Sep 2026 06:56:45 +0200 Message-ID: <20260904045734.863346883@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045734.806166532@linuxfoundation.org> References: <20260904045734.806166532@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yang Erkun [ Upstream commit 13017b427118f4311471ee47df74872372ca8482 ] Our testcase trigger panic: BUG: kernel NULL pointer dereference, address: 00000000000000e0 ... Oops: Oops: 0000 [#1] SMP NOPTI CPU: 2 UID: 0 PID: 85 Comm: kworker/2:1 Not tainted 6.16.0+ #94 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Workqueue: md_misc md_start_sync RIP: 0010:rdev_addable+0x4d/0xf0 ... Call Trace: md_start_sync+0x329/0x480 process_one_work+0x226/0x6d0 worker_thread+0x19e/0x340 kthread+0x10f/0x250 ret_from_fork+0x14d/0x180 ret_from_fork_asm+0x1a/0x30 Modules linked in: raid10 CR2: 00000000000000e0 ---[ end trace 0000000000000000 ]--- RIP: 0010:rdev_addable+0x4d/0xf0 md_spares_need_change in md_start_sync will call rdev_addable which protected by rcu_read_lock/rcu_read_unlock. This rcu context will help protect rdev won't be released, but rdev->mddev will be set to NULL before we call synchronize_rcu in md_kick_rdev_from_array. Fix this by using READ_ONCE and check does rdev->mddev still alive. Fixes: bc08041b32ab ("md: suspend array in md_start_sync() if array need reconfiguration") Fixes: 570b9147deb6 ("md: use RCU lock to protect traversal in md_spares_need_change()") Signed-off-by: Yang Erkun Link: https://lore.kernel.org/linux-raid/20250731114530.776670-1-yangerkun@huawei.com Signed-off-by: Yu Kuai Signed-off-by: Sasha Levin --- drivers/md/md.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 1aff3e541ceb5..60a07d7264d83 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -9373,6 +9373,12 @@ static bool rdev_is_spare(struct md_rdev *rdev) static bool rdev_addable(struct md_rdev *rdev) { + struct mddev *mddev; + + mddev = READ_ONCE(rdev->mddev); + if (!mddev) + return false; + /* rdev is already used, don't add it again. */ if (test_bit(Candidate, &rdev->flags) || rdev->raid_disk >= 0 || test_bit(Faulty, &rdev->flags)) @@ -9383,7 +9389,7 @@ static bool rdev_addable(struct md_rdev *rdev) return true; /* Allow to add if array is read-write. */ - if (md_is_rdwr(rdev->mddev)) + if (md_is_rdwr(mddev)) return true; /* -- 2.53.0