From patchwork Fri Nov 8 10:01:47 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Liu Shixin X-Patchwork-Id: 13867862 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) (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 015744431; Fri, 8 Nov 2024 10:03:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.255 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731060235; cv=none; b=rwn7zNub7DbVy2k+D+TsCXgDovoUqQC7rrew1wcoysOS+DBeTtRh8ojRMODFilUBV+Zc7p9kbY+DMVEM1fEnlpTXZyo7n1Db9G6eV7EcjgY7X8hdT6jcw3nqJoDPiM3vIdewsVD6vKnIjLFAadTQsaLEM7TzutstDzb6O2gT+hI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731060235; c=relaxed/simple; bh=l5DnvzL4sy5C2lpQdy/WOoP4Io2r2vU4GWYByRNWdbw=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=Tw8SaDTVc9oztkLMYQGr44KSW0PUonNvQC2TbbfdcK/5YG0E3U3CHmosGOj4l+9KRSbR0RmB5OSVvbAxLZBnLN46AenB+ISoqMUcKnPzPbye8Vt+IjyPkEcTEYTXZ4B4pMEFqrR4DMEtiWk06xDnVsQZ7MDTskLH20a7rMbh9iM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.255 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.194]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4XlDx23Xptz1T9vC; Fri, 8 Nov 2024 18:01:26 +0800 (CST) Received: from kwepemg200013.china.huawei.com (unknown [7.202.181.64]) by mail.maildlp.com (Postfix) with ESMTPS id 0AC6A1400DC; Fri, 8 Nov 2024 18:03:49 +0800 (CST) Received: from huawei.com (10.175.113.32) by kwepemg200013.china.huawei.com (7.202.181.64) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Fri, 8 Nov 2024 18:03:48 +0800 From: Liu Shixin To: Minchan Kim , Sergey Senozhatsky , Jens Axboe , Andrew Morton CC: , , Liu Shixin Subject: [PATCH] zram: fix NULL pointer in comp_algorithm_show() Date: Fri, 8 Nov 2024 18:01:47 +0800 Message-ID: <20241108100147.3776123-1-liushixin2@huawei.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemg200013.china.huawei.com (7.202.181.64) LTP reported a NULL pointer dereference as followed: CPU: 7 UID: 0 PID: 5995 Comm: cat Kdump: loaded Not tainted 6.12.0-rc6+ #3 Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : __pi_strcmp+0x24/0x140 lr : zcomp_available_show+0x60/0x100 [zram] sp : ffff800088b93b90 x29: ffff800088b93b90 x28: 0000000000000001 x27: 0000000000400cc0 x26: 0000000000000ffe x25: ffff80007b3e2388 x24: 0000000000000000 x23: ffff80007b3e2390 x22: ffff0004041a9000 x21: ffff80007b3e2900 x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: ffff80007b3e2900 x9 : ffff80007b3cb280 x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000 x5 : 0000000000000040 x4 : 0000000000000000 x3 : 00656c722d6f7a6c x2 : 0000000000000000 x1 : ffff80007b3e2900 x0 : 0000000000000000 Call trace: __pi_strcmp+0x24/0x140 comp_algorithm_show+0x40/0x70 [zram] dev_attr_show+0x28/0x80 sysfs_kf_seq_show+0x90/0x140 kernfs_seq_show+0x34/0x48 seq_read_iter+0x1d4/0x4e8 kernfs_fop_read_iter+0x40/0x58 new_sync_read+0x9c/0x168 vfs_read+0x1a8/0x1f8 ksys_read+0x74/0x108 __arm64_sys_read+0x24/0x38 invoke_syscall+0x50/0x120 el0_svc_common.constprop.0+0xc8/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x38/0x138 el0t_64_sync_handler+0xc0/0xc8 el0t_64_sync+0x188/0x190 The zram->comp_algs[ZRAM_PRIMARY_COMP] can be NULL in zram_add() if comp_algorithm_set() has not been called. User can access the zram device by sysfs after device_add_disk(), so there is a time window to trigger the NULL pointer dereference. Move it ahead device_add_disk() to make sure when user can access the zram device, it is ready. comp_algorithm_set() is protected by zram->init_lock in other places and no such problem. Fixes: 7ac07a26dea7 ("zram: preparation for multi-zcomp support") Signed-off-by: Liu Shixin Reviewed-by: Sergey Senozhatsky --- drivers/block/zram/zram_drv.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index ad9c9bc3ccfc..5223a03cb10e 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -2381,6 +2381,8 @@ static int zram_add(void) zram->disk->fops = &zram_devops; zram->disk->private_data = zram; snprintf(zram->disk->disk_name, 16, "zram%d", device_id); + zram_comp_params_reset(zram); + comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor); /* Actual capacity set using sysfs (/sys/block/zram/disksize */ set_capacity(zram->disk, 0); @@ -2388,9 +2390,6 @@ static int zram_add(void) if (ret) goto out_cleanup_disk; - zram_comp_params_reset(zram); - comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor); - zram_debugfs_register(zram); pr_info("Added device: %s\n", zram->disk->disk_name); return device_id;