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 4.15-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-4.15 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;
@@ -351,8 +353,6 @@ static const struct blk_mq_ops ubiblock_
.init_request = ubiblock_init_request,
};
-static DEFINE_IDR(ubiblock_minor_idr);
-
int ubiblock_create(struct ubi_volume_info *vi)
{
struct ubiblock *dev;
@@ -365,14 +365,15 @@ 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);
@@ -437,14 +438,13 @@ 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:
@@ -457,6 +457,8 @@ out_put_disk:
put_disk(dev->gd);
out_free_dev:
kfree(dev);
+out_unlock:
+ mutex_unlock(&devices_mutex);
return ret;
}
@@ -478,30 +480,36 @@ 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)
@@ -630,6 +638,7 @@ 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);
@@ -638,6 +647,7 @@ 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-4.15/ubi-block-fix-locking-for-idr_alloc-idr_remove.patch