Dan Williams 3a198886ab sysfs: handle 'parent deleted before child added' ... In scsi at least two cases of the parent device being deleted before the child is added have been observed. 1/ scsi is performing async scans and the device is removed prior to the async can thread running (can happen with an in-opportune / unlikely unplug during initial scan). 2/ libsas discovery event running after the parent port has been torn down (this is a bug in libsas). Result in crash signatures like: BUG: unable to handle kernel NULL pointer dereference at 0000000000000098 IP: [<ffffffff8115e100>] sysfs_create_dir+0x32/0xb6 ... Process scsi_scan_8 (pid: 5417, threadinfo ffff88080bd16000, task ffff880801b8a0b0) Stack: 00000000fffffffe ffff880813470628 ffff88080bd17cd0 ffff88080614b7e8 ffff88080b45c108 00000000fffffffe ffff88080bd17d20 ffffffff8125e4a8 ffff88080bd17cf0 ffffffff81075149 ffff88080bd17d30 ffff88080614b7e8 Call Trace: [<ffffffff8125e4a8>] kobject_add_internal+0x120/0x1e3 [<ffffffff81075149>] ? trace_hardirqs_on+0xd/0xf [<ffffffff8125e641>] kobject_add_varg+0x41/0x50 [<ffffffff8125e70b>] kobject_add+0x64/0x66 [<ffffffff8131122b>] device_add+0x12d/0x63a In this scenario the parent is still valid (because we have a reference), but it has been device_del()'d which means its kobj->sd pointer is NULL'd via: device_del()->kobject_del()->sysfs_remove_dir() ...and then sysfs_create_dir() (without this fix) goes ahead and de-references parent_sd via sysfs_ns_type(): return (sd->s_flags & SYSFS_NS_TYPE_MASK) >> SYSFS_NS_TYPE_SHIFT; This scenario is being fixed in scsi/libsas, but if other subsystems present the same ordering the system need not immediately crash. Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: James Bottomley <JBottomley@parallels.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2012-04-10 14:48:51 -07:00
..
bin.c
dir.c	sysfs: handle 'parent deleted before child added'	2012-04-10 14:48:51 -07:00
file.c	sysfs: Complain bitterly about attempts to remove files from nonexistent directories.	2012-01-24 12:12:32 -08:00
group.c	sysfs: Prevent crash on unset sysfs group attributes	2012-04-10 14:48:51 -07:00
inode.c	Revert "sysfs: Kill nlink counting."	2012-03-08 13:03:10 -08:00
Kconfig
Makefile
mount.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2012-03-21 13:36:41 -07:00
symlink.c
sysfs.h	Revert "sysfs: Kill nlink counting."	2012-03-08 13:03:10 -08:00