From mboxrd@z Thu Jan 1 00:00:00 1970 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 9FF3E23AB86; Thu, 3 Jul 2025 14:48:35 +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=1751554115; cv=none; b=KLRr0zFzn9ALqiExBZoHC/jqdy+NxOxxXYU4eRaE9Il8wgaGPAA5NHTfSnaVyUL/zyxMmvgidVY4o0RTTRfe0SIXVeIIQuzOXWPXwMBcHnuCGvwCkfpGlpKmtpjkY1kMaH6u4ztaB154c/isKgUUp5MRiYuotQkrBXzzJfIlc5Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751554115; c=relaxed/simple; bh=/2VszAu5ZyiUZHhQHcMmbgRKe6RUzOvzWWZusXBh4PQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XfpWIcE2aDXCrT4cvoQ80fGjWvChIG6IxEChvNNfQN01ztQQ94eUNpPkFm+TKWS/F9mSC1kF0inF5k4sKkQuWVj4JbOfztPm8weQu2X2mhPtsB1h21ghYgoCY506s3VIMvu1NlOoU7vTMWu5VKNG5i/4pQckAteN9rKP168GPms= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kqEuMOy5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kqEuMOy5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FFE0C4CEE3; Thu, 3 Jul 2025 14:48:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1751554115; bh=/2VszAu5ZyiUZHhQHcMmbgRKe6RUzOvzWWZusXBh4PQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kqEuMOy5tPQMRqfjNoC0QTazZWKs/M1prDV/7xzfGhMSajsGhzYu0PS8W9kUjI8Zs 3Mml+T1wCvtZSq4sTn9IqZC9MBt+2optlHdrs4UWYWs/cpaCgK2Wfq0ZP4G/En28gm YYEwn27v0tvqTA7vgq7AVHXvvL3/VJecyq+lIQFM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Kuai , Ming Lei , Jens Axboe , ErKun Yang , John Garry , Thomas Gleinxer , "zhangyi (F)" , Andrew Morton Subject: [PATCH 6.12 085/218] lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly() Date: Thu, 3 Jul 2025 16:40:33 +0200 Message-ID: <20250703143959.340566195@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250703143955.956569535@linuxfoundation.org> References: <20250703143955.956569535@linuxfoundation.org> User-Agent: quilt/0.68 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: Yu Kuai commit df831e97739405ecbaddb85516bc7d4d1c933d6b upstream. While testing null_blk with configfs, echo 0 > poll_queues will trigger following panic: BUG: kernel NULL pointer dereference, address: 0000000000000010 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 27 UID: 0 PID: 920 Comm: bash Not tainted 6.15.0-02023-gadbdb95c8696-dirty #1238 PREEMPT(undef) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:__bitmap_or+0x48/0x70 Call Trace: __group_cpus_evenly+0x822/0x8c0 group_cpus_evenly+0x2d9/0x490 blk_mq_map_queues+0x1e/0x110 null_map_queues+0xc9/0x170 [null_blk] blk_mq_update_queue_map+0xdb/0x160 blk_mq_update_nr_hw_queues+0x22b/0x560 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk] nullb_device_poll_queues_store+0xa4/0x130 [null_blk] configfs_write_iter+0x109/0x1d0 vfs_write+0x26e/0x6f0 ksys_write+0x79/0x180 __x64_sys_write+0x1d/0x30 x64_sys_call+0x45c4/0x45f0 do_syscall_64+0xa5/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e Root cause is that numgrps is set to 0, and ZERO_SIZE_PTR is returned from kcalloc(), and later ZERO_SIZE_PTR will be deferenced. Fix the problem by checking numgrps first in group_cpus_evenly(), and return NULL directly if numgrps is zero. [yukuai3@huawei.com: also fix the non-SMP version] Link: https://lkml.kernel.org/r/20250620010958.1265984-1-yukuai1@huaweicloud.com Link: https://lkml.kernel.org/r/20250619132655.3318883-1-yukuai1@huaweicloud.com Fixes: 6a6dcae8f486 ("blk-mq: Build default queue map via group_cpus_evenly()") Signed-off-by: Yu Kuai Reviewed-by: Ming Lei Reviewed-by: Jens Axboe Cc: ErKun Yang Cc: John Garry Cc: Thomas Gleinxer Cc: "zhangyi (F)" Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- lib/group_cpus.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/lib/group_cpus.c +++ b/lib/group_cpus.c @@ -352,6 +352,9 @@ struct cpumask *group_cpus_evenly(unsign int ret = -ENOMEM; struct cpumask *masks = NULL; + if (numgrps == 0) + return NULL; + if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL)) return NULL; @@ -426,8 +429,12 @@ struct cpumask *group_cpus_evenly(unsign #else /* CONFIG_SMP */ struct cpumask *group_cpus_evenly(unsigned int numgrps) { - struct cpumask *masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL); + struct cpumask *masks; + if (numgrps == 0) + return NULL; + + masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL); if (!masks) return NULL;