This is a note to let you know that I've just added the patch titled ubi: block: Fix locking for idr_alloc/idr_remove to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ubi-block-fix-locking-for-idr_alloc-idr_remove.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 7f29ae9f977bcdc3654e68bc36d170223c52fd48 Mon Sep 17 00:00:00 2001 From: Bradley Bolen <bradleybolen@xxxxxxxxx> Date: Thu, 18 Jan 2018 08:55:20 -0500 Subject: ubi: block: Fix locking for idr_alloc/idr_remove From: Bradley Bolen <bradleybolen@xxxxxxxxx> commit 7f29ae9f977bcdc3654e68bc36d170223c52fd48 upstream. This fixes a race with idr_alloc where gd->first_minor can be set to the same value for two simultaneous calls to ubiblock_create. Each instance calls device_add_disk with the same first_minor. device_add_disk calls bdi_register_owner which generates several warnings. WARNING: CPU: 1 PID: 179 at kernel-source/fs/sysfs/dir.c:31 sysfs_warn_dup+0x68/0x88 sysfs: cannot create duplicate filename '/devices/virtual/bdi/252:2' WARNING: CPU: 1 PID: 179 at kernel-source/lib/kobject.c:240 kobject_add_internal+0x1ec/0x2f8 kobject_add_internal failed for 252:2 with -EEXIST, don't try to register things with the same name in the same directory WARNING: CPU: 1 PID: 179 at kernel-source/fs/sysfs/dir.c:31 sysfs_warn_dup+0x68/0x88 sysfs: cannot create duplicate filename '/dev/block/252:2' However, device_add_disk does not error out when bdi_register_owner returns an error. Control continues until reaching blk_register_queue. It then BUGs. kernel BUG at kernel-source/fs/sysfs/group.c:113! [<c01e26cc>] (internal_create_group) from [<c01e2950>] (sysfs_create_group+0x20/0x24) [<c01e2950>] (sysfs_create_group) from [<c00e3d38>] (blk_trace_init_sysfs+0x18/0x20) [<c00e3d38>] (blk_trace_init_sysfs) from [<c02bdfbc>] (blk_register_queue+0xd8/0x154) [<c02bdfbc>] (blk_register_queue) from [<c02cec84>] (device_add_disk+0x194/0x44c) [<c02cec84>] (device_add_disk) from [<c0436ec8>] (ubiblock_create+0x284/0x2e0) [<c0436ec8>] (ubiblock_create) from [<c0427bb8>] (vol_cdev_ioctl+0x450/0x554) [<c0427bb8>] (vol_cdev_ioctl) from [<c0189110>] (vfs_ioctl+0x30/0x44) [<c0189110>] (vfs_ioctl) from [<c01892e0>] (do_vfs_ioctl+0xa0/0x790) [<c01892e0>] (do_vfs_ioctl) from [<c0189a14>] (SyS_ioctl+0x44/0x68) [<c0189a14>] (SyS_ioctl) from [<c0010640>] (ret_fast_syscall+0x0/0x34) Locking idr_alloc/idr_remove removes the race and keeps gd->first_minor unique. Fixes: 2bf50d42f3a4 ("UBI: block: Dynamically allocate minor numbers") Signed-off-by: Bradley Bolen <bradleybolen@xxxxxxxxx> Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> Signed-off-by: Richard Weinberger <richard@xxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/mtd/ubi/block.c | 42 ++++++++++++++++++++++++++---------------- 1 file changed, 26 insertions(+), 16 deletions(-) --- a/drivers/mtd/ubi/block.c +++ b/drivers/mtd/ubi/block.c @@ -99,6 +99,8 @@ struct ubiblock { /* Linked list of all ubiblock instances */ static LIST_HEAD(ubiblock_devices); +static DEFINE_IDR(ubiblock_minor_idr); +/* Protects ubiblock_devices and ubiblock_minor_idr */ static DEFINE_MUTEX(devices_mutex); static int ubiblock_major; @@ -354,8 +356,6 @@ static struct blk_mq_ops ubiblock_mq_ops .map_queue = blk_mq_map_queue, }; -static DEFINE_IDR(ubiblock_minor_idr); - int ubiblock_create(struct ubi_volume_info *vi) { struct ubiblock *dev; @@ -368,14 +368,15 @@ int ubiblock_create(struct ubi_volume_in /* Check that the volume isn't already handled */ mutex_lock(&devices_mutex); if (find_dev_nolock(vi->ubi_num, vi->vol_id)) { - mutex_unlock(&devices_mutex); - return -EEXIST; + ret = -EEXIST; + goto out_unlock; } - mutex_unlock(&devices_mutex); dev = kzalloc(sizeof(struct ubiblock), GFP_KERNEL); - if (!dev) - return -ENOMEM; + if (!dev) { + ret = -ENOMEM; + goto out_unlock; + } mutex_init(&dev->dev_mutex); @@ -440,14 +441,13 @@ int ubiblock_create(struct ubi_volume_in goto out_free_queue; } - mutex_lock(&devices_mutex); list_add_tail(&dev->list, &ubiblock_devices); - mutex_unlock(&devices_mutex); /* Must be the last step: anyone can call file ops from now on */ add_disk(dev->gd); dev_info(disk_to_dev(dev->gd), "created from ubi%d:%d(%s)", dev->ubi_num, dev->vol_id, vi->name); + mutex_unlock(&devices_mutex); return 0; out_free_queue: @@ -460,6 +460,8 @@ out_put_disk: put_disk(dev->gd); out_free_dev: kfree(dev); +out_unlock: + mutex_unlock(&devices_mutex); return ret; } @@ -481,30 +483,36 @@ static void ubiblock_cleanup(struct ubib int ubiblock_remove(struct ubi_volume_info *vi) { struct ubiblock *dev; + int ret; mutex_lock(&devices_mutex); dev = find_dev_nolock(vi->ubi_num, vi->vol_id); if (!dev) { - mutex_unlock(&devices_mutex); - return -ENODEV; + ret = -ENODEV; + goto out_unlock; } /* Found a device, let's lock it so we can check if it's busy */ mutex_lock(&dev->dev_mutex); if (dev->refcnt > 0) { - mutex_unlock(&dev->dev_mutex); - mutex_unlock(&devices_mutex); - return -EBUSY; + ret = -EBUSY; + goto out_unlock_dev; } /* Remove from device list */ list_del(&dev->list); - mutex_unlock(&devices_mutex); - ubiblock_cleanup(dev); mutex_unlock(&dev->dev_mutex); + mutex_unlock(&devices_mutex); + kfree(dev); return 0; + +out_unlock_dev: + mutex_unlock(&dev->dev_mutex); +out_unlock: + mutex_unlock(&devices_mutex); + return ret; } static int ubiblock_resize(struct ubi_volume_info *vi) @@ -633,6 +641,7 @@ static void ubiblock_remove_all(void) struct ubiblock *next; struct ubiblock *dev; + mutex_lock(&devices_mutex); list_for_each_entry_safe(dev, next, &ubiblock_devices, list) { /* The module is being forcefully removed */ WARN_ON(dev->desc); @@ -641,6 +650,7 @@ static void ubiblock_remove_all(void) ubiblock_cleanup(dev); kfree(dev); } + mutex_unlock(&devices_mutex); } int __init ubiblock_init(void) Patches currently in stable-queue which might be from bradleybolen@xxxxxxxxx are queue-4.4/ubi-block-fix-locking-for-idr_alloc-idr_remove.patch