Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 23 Nov 2002 07:15:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 23 Nov 2002 07:15:14 -0500 Received: from angband.namesys.com ([212.16.7.85]:10631 "HELO angband.namesys.com") by vger.kernel.org with SMTP id ; Sat, 23 Nov 2002 07:15:13 -0500 Date: Sat, 23 Nov 2002 15:22:23 +0300 From: Oleg Drokin To: mochel@osdl.org, linux-kernel@vger.kernel.org Subject: Problem in using kobjects for block devices and partitions Message-ID: <20021123152223.A17314@namesys.com> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline User-Agent: Mutt/1.3.22.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2716 Lines: 70 Hello! Problem code is in register_disk, and though it was included at the end of November, but problems started to appear very recently. At the beginning of register_disk() we see this snippet: s = strchr(disk->kobj.name, '/'); if (s) *s = '!'; kobject_register(&disk->kobj); disk_sysfs_symlinks(disk); And now kobject_register() frees disk structure if registration was unsuccesful, so doing anything else with this structure is not very nice thing. This is especially observable if you turn on SLAB poisoning, then it will die during disk_sysfs_symlinks (actually two levels deeper). I think here we should at least check return value of kobject_register and print something useful. This won't help much against crashing since accessing /proc/partition afterwards will still kill the box (in case of SLAB poisoning, otherwise some other unpredictable stuff will happen). It seems that making register_disk() to return error back to caller does not makes much sence either, since struct gendisk is already destroyed and we cannot get it off the lists that easily. May be it was just a bad decision to destroy whole structure of underlying object when kobject creation have failed? Anyway at least below patch is a good thing to easy problem diagnostics when kobject_register() fails during registering block devices (e.g. because some of them have same base name). Bye, Oleg ===== fs/partitions/check.c 1.88 vs edited ===== --- 1.88/fs/partitions/check.c Thu Nov 21 06:08:39 2002 +++ edited/fs/partitions/check.c Sat Nov 23 15:17:28 2002 @@ -400,13 +400,23 @@ struct block_device *bdev; char *s; int j; + int error; + /* In case of error disk structure will be freed, so we cannot + dereference it. Let's save some useful info so that we can + print meaningful error message. */ + int minor=disk->first_minor, major=disk->major; strncpy(disk->kobj.name,disk->disk_name,KOBJ_NAME_LEN); /* ewww... some of these buggers have / in name... */ s = strchr(disk->kobj.name, '/'); if (s) *s = '!'; - kobject_register(&disk->kobj); + + error = kobject_register(&disk->kobj); + if ( error ) { + printk(KERN_ERR "%s: Failed to create kernel object for disk major %d, first minor %d. Reason: %d\n", __FUNCTION__, major, minor, error ); + return; + } disk_sysfs_symlinks(disk); if (disk->flags & GENHD_FL_CD) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/