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 96EF54EFFA9; Thu, 17 Sep 2026 16:05:29 +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=1789661130; cv=none; b=YYmRDxYHbfKrFv9rWGBXJKMDdobIGquhLrUEBJhvhMjl/htZMjlsGO5VcrHWN5P93QJykQCjt8MxI7nZa6frapJUnb8xzPZAKrbGyXHMi8CricL690Q3J2a1cWmF0JLYnZ/QItjv5HXG9BXZc8r78FIxyRAV5dsFpTFHb1yGFjA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789661130; c=relaxed/simple; bh=iGpV/xFqxKpCFGAEb/V1y/rRx74gJTOvgEA04H8Ibkg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QrFiIAacgwikyLK3M+eFTicSKqQvBjvrd9crBC9L8XwNk1Ca+BC0xmv2SkHPGqkUBVDiwddaoxuWlw3StW6/4H4aDBjZs5RHWR1kzSTf83s6JpU+0YkHff63whDyNpe1kE9I23dPD7x/9zZ2EjluDiRLCtB2dJLsQljFEmFFoCs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=N1JuZUlo; 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="N1JuZUlo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FC5B1F000FF; Thu, 17 Sep 2026 16:05:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789661129; bh=s8qJd4o4S7x8iIclb6xXwPUwL3cDjQ5fM+2RASND+8Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=N1JuZUloifm7E9Dz+BBO5Ey16IekfvimPm+xpmFJ3/MtwRCiMgrv2o49RcHG9K7/E ew2OEzvZemT4cuKUNGGovoYQAW1lIHsFE8RaqcXWkeSnugZWy8DXIQxhHEaHJoj8Mb CUB6xx+UunxeFJlfh+3swaqkgecf1apNmW8rqdLw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Shawn Lin , Ulf Hansson , Sasha Levin Subject: [PATCH 6.18 0093/1250] mmc: core: Add validation for host-provided max_segs Date: Thu, 17 Sep 2026 15:58:08 +0100 Message-ID: <20260917151554.507400732@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151551.901433442@linuxfoundation.org> References: <20260917151551.901433442@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Shawn Lin [ Upstream commit 3e0483e93a8be320f70a1ff68d835f7f015af311 ] The max_segs field is of type unsigned short, and if a host driver sets an excessively large value, it may be truncated to zero. This can cause mmc_alloc_sg() to call kmalloc_objs() with a zero size allocation request, which leads to undefined behavior. Under the SLUB allocator, kmalloc(0) returns a special pointer (ZERO_SIZE_PTR). The subsequent 'if (sg)' check will evaluate to true, and sg_init_table() will then attempt to access invalid memory, resulting in a crash: dwmmc_rockchip 2a310000.mmc: Successfully tuned phase to 133 mmc1: new UHS-I speed SDR104 SDHC card at address aaaa Unable to handle kernel paging request at virtual address 0000001ffffffff0 Mem abort info: ESR = 0x0000000096000004 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x04: level 0 translation fault Data abort info: ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 4k pages, 48-bit VAs, pgdp=0000000102c88000 [0000001ffffffff0] pgd=0000000000000000, p4d=0000000000000000 Internal error: Oops: 0000000096000004 [#1] SMP Modules linked in: CPU: 2 UID: 0 PID: 102 Comm: kworker/2:1 Not tainted 7.0.0-rc6-next-20260331-00013-g4d93c25963c5-dirty #80 PREEMPT Hardware name: Rockchip RK3576 EVB V10 Board (DT) Workqueue: events_freezable mmc_rescan pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : sg_init_table+0x2c/0x50 lr : sg_init_table+0x24/0x50 sp : ffff8000837db710 x29: ffff8000837db710 x28: 000000000000c000 x27: 0000000000000300 x26: 0000000000000000 x25: 0000000000000040 x24: ffff0000c46a0000 x23: 0000000000000000 x22: ffff0000c0c73c00 x21: 0000000000000010 x20: 0000000000000010 x19: 0000000000000000 x18: 000000000000002c x17: 0000000000000000 x16: 0000000000000001 x15: 0000000000000000 x14: 0000000000000400 x13: ffff8000837dc000 x12: 0000000000000000 x11: ffff0000c0c73ca0 x10: 0000000000000040 x9 : 459ec1f0abbdbb00 x8 : 0000001fffffffe0 x7 : 0000000000000000 x6 : 000000000000003f x5 : 0000000000035579 x4 : 0000000000000901 x3 : 0000000000000000 x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000010 Call trace: sg_init_table+0x2c/0x50 (P) mmc_mq_init_request+0x64/0x90 blk_mq_alloc_map_and_rqs+0x3ac/0x480 blk_mq_alloc_set_map_and_rqs+0x98/0x1e0 blk_mq_alloc_tag_set+0x1c0/0x290 mmc_init_queue+0x120/0x370 mmc_blk_alloc_req+0x150/0x420 To prevent this, add a validation check in mmc_mq_init_request() to detect when sg_len (derived from max_segs) is zero. If sg_len is zero, we return an error and print an error message, allowing host driver developers to identify and fix incorrect max_segs configuration. This is a defensive measure that ensures the MMC core fails gracefully when host drivers provide invalid max_segs values, rather than crashing with a page fault. Signed-off-by: Shawn Lin Signed-off-by: Ulf Hansson Signed-off-by: Sasha Levin --- drivers/mmc/core/queue.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c index eb1053d8cae72..eb25a0825adcf 100644 --- a/drivers/mmc/core/queue.c +++ b/drivers/mmc/core/queue.c @@ -214,8 +214,14 @@ static int mmc_mq_init_request(struct blk_mq_tag_set *set, struct request *req, struct mmc_queue *mq = set->driver_data; struct mmc_card *card = mq->card; struct mmc_host *host = card->host; + u16 sg_len = mmc_get_max_segments(host); - mq_rq->sg = mmc_alloc_sg(mmc_get_max_segments(host), GFP_KERNEL); + if (!sg_len) { + dev_err(mmc_dev(host), "Wrong max_segs assigned\n"); + return -EINVAL; + } + + mq_rq->sg = mmc_alloc_sg(sg_len, GFP_KERNEL); if (!mq_rq->sg) return -ENOMEM; -- 2.53.0