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 079852F235E; Thu, 3 Jul 2025 15:13:59 +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=1751555639; cv=none; b=hcegztRgdoDh1m92Q1okZO1UTLmIWAi2Jd93b8BNxyq20NfSOE1+NrJ254lGrEh2ifdVGCinGVWelTm9VrsGjQDhlslFoY7/kutCgwDuqkkzdUUbE9VRdp0qHCbzU7J+xb+9E2a0KnQOY6hpSzSXuXNX/canEeRu07AfJ9M6COw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751555639; c=relaxed/simple; bh=raF2Q6BfDGIlraJEgMgRPRV25WDmD0u7VVkdblm92xc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uPppWdC+2dg9yS/KpbN9EU12qjfevydv3o3ThDLS19QPKucqdDt61tm9hwGajxGc0I/CC6KI6DMSrjmVcMGhyQgRyPNPBRlWRfAWod6Em6dDqZElmll21xHvXG62A+8G1TY9+gHbYpbw3d10FDeoWWN4lGHfBJlfHhDzESZPrgw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=w32T5q4H; 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="w32T5q4H" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EF24C4CEEE; Thu, 3 Jul 2025 15:13:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1751555638; bh=raF2Q6BfDGIlraJEgMgRPRV25WDmD0u7VVkdblm92xc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w32T5q4HLQmdOnhVslP9Gm7utGgWcWK/bJUYPhMDjP7LWmdMjo6YSn0OGKBo5NGfC L+kXwFeh04oBBJBdiX/bR4mVEbuEsat85B2lIw0QLZTEtfHqUyVfPlC0obvsnInXdw IDJEj/QqSDe/ReqfuQBzsCzldndGCyI3issNJnN4= 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 6.6 076/139] lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly() Date: Thu, 3 Jul 2025 16:42:19 +0200 Message-ID: <20250703143944.139816089@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250703143941.182414597@linuxfoundation.org> References: <20250703143941.182414597@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-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(-) diff --git a/lib/group_cpus.c b/lib/group_cpus.c index ee272c4cefcc..18d43a406114 100644 --- a/lib/group_cpus.c +++ b/lib/group_cpus.c @@ -352,6 +352,9 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps) 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(unsigned int numgrps) #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; -- 2.50.0