linux-stable.git/drivers/target/target_core_device.c, branch linux-4.18.y

scsi: target: Avoid that EXTENDED COPY commands trigger lock inversion

2018-10-03T23:59:08+00:00

[ Upstream commit 36d4cb460bcbe2a1323732a6e4bb9dd783284368 ]

The approach for adding a device to the devices_idr data structure and for
removing it is as follows:

* &dev->dev_group.cg_item is initialized before a device is added to
  devices_idr.

* If the reference count of a device drops to zero then
  target_free_device() removes the device from devices_idr.

* All devices_idr manipulations are protected by device_mutex.

This means that increasing the reference count of a device is sufficient to
prevent removal from devices_idr and also that it is safe access
dev_group.cg_item for any device that is referenced by devices_idr. Use
this to modify target_find_device() and target_for_each_device() such that
these functions no longer introduce a dependency between device_mutex and
the configfs root inode mutex.

Note: it is safe to pass a NULL pointer to config_item_put() and also to
config_item_get_unless_zero().

This patch prevents that lockdep reports the following complaint:

======================================================
WARNING: possible circular locking dependency detected
4.12.0-rc1-dbg+ #1 Not tainted
------------------------------------------------------
rmdir/12053 is trying to acquire lock:
 (device_mutex#2){+.+.+.}, at: []
target_free_device+0xae/0xf0 [target_core_mod]

but task is already holding lock:
 (&sb->s_type->i_mutex_key#14){++++++}, at: []
vfs_rmdir+0x50/0x140

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&sb->s_type->i_mutex_key#14){++++++}:
       lock_acquire+0x59/0x80
       down_write+0x36/0x70
       configfs_depend_item+0x3a/0xb0 [configfs]
       target_depend_item+0x13/0x20 [target_core_mod]
       target_xcopy_locate_se_dev_e4_iter+0x87/0x100 [target_core_mod]
       target_devices_idr_iter+0x16/0x20 [target_core_mod]
       idr_for_each+0x39/0xc0
       target_for_each_device+0x36/0x50 [target_core_mod]
       target_xcopy_locate_se_dev_e4+0x28/0x80 [target_core_mod]
       target_xcopy_do_work+0x2e9/0xdd0 [target_core_mod]
       process_one_work+0x1ca/0x3f0
       worker_thread+0x49/0x3b0
       kthread+0x109/0x140
       ret_from_fork+0x31/0x40

-> #0 (device_mutex#2){+.+.+.}:
       __lock_acquire+0x101f/0x11d0
       lock_acquire+0x59/0x80
       __mutex_lock+0x7e/0x950
       mutex_lock_nested+0x16/0x20
       target_free_device+0xae/0xf0 [target_core_mod]
       target_core_dev_release+0x10/0x20 [target_core_mod]
       config_item_put+0x6e/0xb0 [configfs]
       configfs_rmdir+0x1a6/0x300 [configfs]
       vfs_rmdir+0xb7/0x140
       do_rmdir+0x1f4/0x200
       SyS_rmdir+0x11/0x20
       entry_SYSCALL_64_fastpath+0x23/0xc2

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#14);
                               lock(device_mutex#2);
                               lock(&sb->s_type->i_mutex_key#14);
  lock(device_mutex#2);

 *** DEADLOCK ***

3 locks held by rmdir/12053:
 #0:  (sb_writers#10){.+.+.+}, at: []
mnt_want_write+0x1f/0x50
 #1:  (&sb->s_type->i_mutex_key#14/1){+.+.+.}, at: []
do_rmdir+0x15e/0x200
 #2:  (&sb->s_type->i_mutex_key#14){++++++}, at: []
vfs_rmdir+0x50/0x140

stack backtrace:
CPU: 3 PID: 12053 Comm: rmdir Not tainted 4.12.0-rc1-dbg+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.0.0-prebuilt.qemu-project.org 04/01/2014
Call Trace:
 dump_stack+0x86/0xcf
 print_circular_bug+0x1c7/0x220
 __lock_acquire+0x101f/0x11d0
 lock_acquire+0x59/0x80
 __mutex_lock+0x7e/0x950
 mutex_lock_nested+0x16/0x20
 target_free_device+0xae/0xf0 [target_core_mod]
 target_core_dev_release+0x10/0x20 [target_core_mod]
 config_item_put+0x6e/0xb0 [configfs]
 configfs_rmdir+0x1a6/0x300 [configfs]
 vfs_rmdir+0xb7/0x140
 do_rmdir+0x1f4/0x200
 SyS_rmdir+0x11/0x20
 entry_SYSCALL_64_fastpath+0x23/0xc2

Signed-off-by: Bart Van Assche 
[Rebased to handle conflict withe target_find_device removal]
Signed-off-by: Mike Christie 

Signed-off-by: Martin K. Petersen 

Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

target: fix destroy device in target_configure_device

2018-01-18T09:21:11+00:00

After dev->transport->configure_device succeeds, target_configure_device
exits abnormally, dev_flags has not set DF_CONFIGURED yet, does not call
destroy_device function in free_device.

Signed-off-by: tangwenji 
Acked-by: Mike Christie 
Signed-off-by: Nicholas Bellinger

target: Fix cmd size for PR-OUT in passthrough_parse_cdb

2017-07-10T03:58:49+00:00

The cmd size should be 4bytes form byte5 to byte8 when CDB opcode
is PERSISTENT_RESERVE_OUT in SPC3 and SPC4

(Also fix up the same in spc_parse_cdb - MNC)

Signed-off-by: Tang Wenji 
Signed-off-by: Nicholas Bellinger

target: Use macro for WRITE_VERIFY_32 operation codes

2017-07-07T06:11:49+00:00

Add WRITE_VERIFY_32 definition to scsi prototypes and use this macro
definition isntead of the hard coded value.

(Drop WRITE_VERIFY_16 that's already part of another patch - nab)

Signed-off-by: Damien Le Moal 
Signed-off-by: Nicholas Bellinger

target: make device_mutex and device_list static

2017-07-07T06:11:44+00:00

Variables device_mutex and device_list static are local to the source,
so make them static.

Cleans up sparse warnings:
"symbol 'device_list' was not declared. Should it be static?"
"symbol 'device_mutex' was not declared. Should it be static?"

Signed-off-by: Colin Ian King 
Signed-off-by: Nicholas Bellinger

target: remove g_device_list

2017-07-07T06:11:41+00:00

g_device_list is no longer needed because we now use the idr code
for lookups and seaches.

Signed-off-by: Mike Christie 
Reviewed-by: Bart Van Assche 
Signed-off-by: Nicholas Bellinger

target: add helper to iterate over devices

2017-07-07T06:11:39+00:00

This adds a wrapper around idr_for_each so the xcopy code can loop over
the devices in the next patch.

Signed-off-by: Mike Christie 
Reviewed-by: Bart Van Assche 
Signed-off-by: Nicholas Bellinger

target: add helper to find se_device by dev_index

2017-07-07T06:11:38+00:00

This adds a helper to find a se_device by dev_index. It will
be used in the next patches so tcmu's netlink interface can
execute commands on specific devices.

Signed-off-by: Mike Christie 
Reviewed-by: Bart Van Assche 
Signed-off-by: Nicholas Bellinger

target: use idr for se_device dev index

2017-07-07T06:11:37+00:00

In the next patches we will add tcmu netlink support that allows
userspace to send commands to target_core_user. To execute operations
on a se_device/tcmu_dev we need to be able to look up a dev by any old
id. This patch replaces the se_device->dev_index with a idr created
id.

The next patches will also remove the g_device_list and replace it with
the idr.

Signed-off-by: Mike Christie 
Signed-off-by: Nicholas Bellinger

target: break up free_device callback

2017-07-07T06:11:37+00:00

With this patch free_device is now used to free what is allocated in the
alloc_device callback and destroy_device tears down the resources that are
setup in the configure_device callback.

This patch will be needed in the next patch where tcmu needs
to be able to look up the device in the destroy callback.

Signed-off-by: Mike Christie 
Reviewed-by: Bart Van Assche 
Signed-off-by: Nicholas Bellinger