Re: [PATCH] scsi: target: Fix data corruption under concurrent target configuration

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ping :)

On 22/05/2023 13:27, Grzegorz Uriasz wrote:
Subject:
Re: [PATCH] scsi: target: Fix data corruption under concurrent target configuration
From:
Grzegorz Uriasz <gorbak25@xxxxxxxxx>
Date:
22/05/2023, 13:27

To:
Dmitry Bogdanov <d.bogdanov@xxxxxxxxx>
CC:
"Martin K. Petersen" <martin.petersen@xxxxxxxxxx>, linux-scsi@xxxxxxxxxxxxxxx, target-devel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, dutkahugo@xxxxxxxxx


Hi Dmitry,
I've added a debug printk call to see whether the devices are enabled concurrently:
---
 drivers/target/target_core_device.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 5054b647dd0b..f594ee86a986 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -910,6 +910,8 @@ int target_configure_device(struct se_device *dev)
         return -EEXIST;
     }

+    pr_err("Configuring %p device", dev);
+
     /*
      * Add early so modules like tcmu can use during its
      * configuration.
--
2.40.0

It turns out that even when the flags are set atomically it seems that there is either no mutex protecting the setup or concurrent kzalloc calls returned the same address:

[ 3179.785908] kobject: 'maps' (000000000fdf10fd): calling ktype release
[ 3179.785910] kobject: (000000000fdf10fd): dynamic_kobj_release
[ 3179.785912] kobject: 'maps': free name
[ 3179.785953] tcmu nl cmd 2/0 completion could not find device with dev id 87.
[ 3179.786015] kobject: 'uio8' (000000001b25d2de): kobject_uevent_env
[ 3179.786315] kobject: 'uio8' (000000001b25d2de): fill_kobj_path: path = '/devices/tcm_user/uio/uio8' [ 3179.786315] tcmu nl cmd 2/0 completion could not find device with dev id 87. [ 3179.786322] tcmu nl cmd 2/0 completion could not find device with dev id 87. [ 3179.786557] kobject: 'uio8' (000000001b25d2de): kobject_cleanup, parent 0000000000000000
[ 3179.786902] kobject: 'uio8' (000000001b25d2de): calling ktype release
[ 3179.786904] kobject: 'uio8': free name
[ 3179.786906] tcmu nl cmd 2/0 completion could not find device with dev id 87. [ 3179.787226] tcmu nl cmd 2/0 completion could not find device with dev id 87. [ 3179.809906] kobject: 'map0' (000000003fa04166): kobject_cleanup, parent 00000000e5849eec [ 3179.809914] kobject: 'map0' (000000003fa04166): auto cleanup kobject_del [ 3179.809930] tcmu nl cmd 2/0 completion could not find device with dev id 89.
[ 3179.809936] kobject: 'map0' (000000003fa04166): calling ktype release
[ 3179.810216] kobject: 'map0': free name
[ 3179.810218] tcmu nl cmd 2/0 completion could not find device with dev id 89. [ 3179.810219] kobject: 'maps' (00000000e5849eec): kobject_cleanup, parent 00000000345aab09 [ 3179.810226] tcmu nl cmd 2/0 completion could not find device with dev id 89. [ 3179.810535] kobject: 'maps' (00000000e5849eec): auto cleanup kobject_del [ 3179.810890] tcmu nl cmd 2/0 completion could not find device with dev id 89.
[ 3179.810890] kobject: 'maps' (00000000e5849eec): calling ktype release
[ 3179.811171] kobject: (00000000e5849eec): dynamic_kobj_release
[ 3179.811174] kobject: 'maps': free name
[ 3179.811195] tcmu nl cmd 2/0 completion could not find device with dev id 89.
[ 3179.811292] kobject: 'uio9' (00000000345aab09): kobject_uevent_env
[ 3179.811546] kobject: 'uio9' (00000000345aab09): fill_kobj_path: path = '/devices/tcm_user/uio/uio9' [ 3179.811576] kobject: 'uio9' (00000000345aab09): kobject_cleanup, parent 0000000000000000
[ 3179.811578] kobject: 'uio9' (00000000345aab09): calling ktype release
[ 3179.811581] kobject: 'uio9': free name
[ 3179.829730] kobject: '0' (00000000981718a9): kobject_cleanup, parent 0000000000000000
[ 3179.829736] kobject: '0' (00000000981718a9): calling ktype release
[ 3179.829740] kobject: '0': free name
[ 3179.829743] kobject: 'cpu0' (00000000155d52b3): kobject_cleanup, parent 0000000000000000
[ 3179.829744] kobject: 'cpu0' (00000000155d52b3): calling ktype release
[ 3179.829746] kobject: 'cpu0': free name
[ 3179.829751] kobject: 'cpu1' (0000000050648bc7): kobject_cleanup, parent 0000000000000000
[ 3179.829753] kobject: 'cpu1' (0000000050648bc7): calling ktype release
[ 3179.829754] kobject: 'cpu1': free name
[ 3179.829755] kobject: 'cpu2' (00000000f0e72c5c): kobject_cleanup, parent 0000000000000000
[ 3179.829757] kobject: 'cpu2' (00000000f0e72c5c): calling ktype release
[ 3179.829758] kobject: 'cpu2': free name
[ 3179.829759] kobject: 'cpu3' (000000000b256e81): kobject_cleanup, parent 0000000000000000
[ 3179.829760] kobject: 'cpu3' (000000000b256e81): calling ktype release
[ 3179.829761] kobject: 'cpu3': free name
[ 3179.829762] kobject: 'cpu4' (000000008d489b4f): kobject_cleanup, parent 0000000000000000
[ 3179.829764] kobject: 'cpu4' (000000008d489b4f): calling ktype release
[ 3179.829765] kobject: 'cpu4': free name
[ 3179.829766] kobject: 'cpu5' (00000000f2e35ad0): kobject_cleanup, parent 0000000000000000
[ 3179.829767] kobject: 'cpu5' (00000000f2e35ad0): calling ktype release
[ 3179.829768] kobject: 'cpu5': free name
[ 3179.829769] kobject: 'cpu6' (00000000ecbd8737): kobject_cleanup, parent 0000000000000000
[ 3179.829771] kobject: 'cpu6' (00000000ecbd8737): calling ktype release
[ 3179.829772] kobject: 'cpu6': free name
[ 3179.829773] kobject: 'cpu7' (00000000813ca063): kobject_cleanup, parent 0000000000000000
[ 3179.829774] kobject: 'cpu7' (00000000813ca063): calling ktype release
[ 3179.829775] kobject: 'cpu7': free name
[ 3179.829776] kobject: 'mq' (0000000062154d34): kobject_cleanup, parent 0000000000000000
[ 3179.829778] kobject: 'mq' (0000000062154d34): calling ktype release
[ 3179.829781] kobject: 'mq': free name
[ 3179.937204] tcmu daemon: command reply support 1.
[ 3180.242175] Configuring 0000000048576d33 device
[ 3180.242191] Configuring 00000000a24b9f12 device
[ 3180.243085] Configuring 0000000048576d33 device
[ 3180.243097] Configuring 0000000048576d33 device
[ 3180.243195] kobject: 'uio8' (00000000d48cde09): kobject_add_internal: parent: 'uio', set: 'devices'
[ 3180.243293] kobject: 'uio8' (00000000d48cde09): kobject_uevent_env
[ 3180.243325] kobject: 'uio9' (0000000025c5cb20): kobject_add_internal: parent: 'uio', set: 'devices'
[ 3180.243388] kobject: 'uio9' (0000000025c5cb20): kobject_uevent_env
[ 3180.243392] kobject: 'uio9' (0000000025c5cb20): fill_kobj_path: path = '/devices/tcm_user/uio/uio9' [ 3180.243419] kobject: 'maps' (000000007f057cf5): kobject_add_internal: parent: 'uio9', set: '<NULL>' [ 3180.243424] kobject: 'map0' (00000000f663b250): kobject_add_internal: parent: 'maps', set: '<NULL>'
[ 3180.243432] kobject: 'map0' (00000000f663b250): kobject_uevent_env
[ 3180.243433] kobject: 'map0' (00000000f663b250): kobject_uevent_env: filter function caused the event to drop!
[ 3180.243565] Configuring 0000000048576d33 device
[ 3180.243598] tcmu nl cmd 1/-2 completion could not find device with dev id 91. [ 3180.243606] tcmu nl cmd 1/-2 completion could not find device with dev id 91. [ 3180.243618] kobject: 'uio8' (00000000d48cde09): fill_kobj_path: path = '/devices/tcm_user/uio/uio8' [ 3180.243622] tcmu nl cmd 1/-2 completion could not find device with dev id 91. [ 3180.243640] kobject: 'maps' (00000000592a7aac): kobject_add_internal: parent: 'uio8', set: '<NULL>' [ 3180.243646] kobject: 'map0' (0000000009bdede6): kobject_add_internal: parent: 'maps', set: '<NULL>'
[ 3180.243656] kobject: 'map0' (0000000009bdede6): kobject_uevent_env
[ 3180.243658] kobject: 'map0' (0000000009bdede6): kobject_uevent_env: filter function caused the event to drop!
[ 3180.243726] se_dev->se_dev_ptr already set for storage object
[ 3180.243731] se_dev->se_dev_ptr already set for storage object
[ 3180.243735] se_dev->se_dev_ptr already set for storage object
[ 3180.243738] se_dev->se_dev_ptr already set for storage object
[ 3180.243742] se_dev->se_dev_ptr already set for storage object
[ 3180.243746] se_dev->se_dev_ptr already set for storage object
[ 3180.243749] se_dev->se_dev_ptr already set for storage object
[ 3180.243760] se_dev->se_dev_ptr already set for storage object
[ 3180.243763] se_dev->se_dev_ptr already set for storage object
[ 3180.243767] se_dev->se_dev_ptr already set for storage object
[ 3180.243777] se_dev->se_dev_ptr already set for storage object
[ 3180.243780] se_dev->se_dev_ptr already set for storage object
[ 3180.243784] se_dev->se_dev_ptr already set for storage object
[ 3180.243788] se_dev->se_dev_ptr already set for storage object
[ 3180.244302] kobject: 'uio10' (000000001e7fdf06): kobject_add_internal: parent: 'uio', set: 'devices' [ 3180.244472] tcmu nl cmd 1/-2 completion could not find device with dev id 93. [ 3180.244628] kobject: 'uio11' (00000000a5f1af78): kobject_add_internal: parent: 'uio', set: 'devices'
[ 3180.244738] kobject: 'uio11' (00000000a5f1af78): kobject_uevent_env
[ 3180.244746] kobject: 'uio10' (000000001e7fdf06): kobject_uevent_env
[ 3180.244753] kobject: 'uio10' (000000001e7fdf06): fill_kobj_path: path = '/devices/tcm_user/uio/uio10' [ 3180.244781] kobject: 'maps' (00000000def336c9): kobject_add_internal: parent: 'uio10', set: '<NULL>' [ 3180.244787] kobject: 'map0' (0000000026045935): kobject_add_internal: parent: 'maps', set: '<NULL>'
[ 3180.244797] kobject: 'map0' (0000000026045935): kobject_uevent_env
[ 3180.244798] kobject: 'map0' (0000000026045935): kobject_uevent_env: filter function caused the event to drop! [ 3180.244820] kobject: 'uio12' (00000000768952da): kobject_add_internal: parent: 'uio', set: 'devices' [ 3180.244837] list_add double add: new=ffff888017480000, prev=ffffffff82e35ba0, next=ffff888017480000. [ 3180.244855] tcmu nl cmd 1/-2 completion could not find device with dev id 93.
[ 3180.244883] kobject: 'uio12' (00000000768952da): kobject_uevent_env
[ 3180.244888] kobject: 'uio12' (00000000768952da): fill_kobj_path: path = '/devices/tcm_user/uio/uio12'
[ 3180.244894] ------------[ cut here ]------------
[ 3180.244897] kernel BUG at lib/list_debug.c:33!
[ 3180.244901] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
[ 3180.244902] kobject: 'maps' (000000008b3ebaee): kobject_add_internal: parent: 'uio12', set: '<NULL>' [ 3180.244903] CPU: 5 PID: 240588 Comm: node Not tainted 6.4.0-rc2hocus-00247-g02bf964976ef-dirty #11 1a56ed25763fc52a0220ba3bab2f1b70cacabece [ 3180.244905] kobject: 'map0' (0000000012d7aa89): kobject_add_internal: parent: 'maps', set: '<NULL>'
[ 3180.244908] kobject: 'map0' (0000000012d7aa89): kobject_uevent_env
[ 3180.244909] kobject: 'map0' (0000000012d7aa89): kobject_uevent_env: filter function caused the event to drop!
[ 3180.244906] RIP: 0010:__list_add_valid+0x94/0xa0
[ 3180.244917] Code: d1 48 89 c6 4c 89 c2 48 c7 c7 38 e1 4b 82 e8 63 25 b3 ff 0f 0b 48 89 f2 48 89 c1 48 89 fe 48 c7 c7 90 e1 4b 82 e8 4c 25 b3 ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90
[ 3180.244918] RSP: 0018:ffffc90002e7fd68 EFLAGS: 00010246
[ 3180.244919] RAX: 0000000000000058 RBX: ffff888017480018 RCX: 0000000000000000 [ 3180.244919] RDX: 0000000000000000 RSI: ffffffff824440d9 RDI: 00000000ffffffff [ 3180.244920] RBP: ffffc90002e7fd68 R08: 0000000000000001 R09: 0000000000000001 [ 3180.244921] R10: 000000001b629664 R11: 0000000000000005 R12: 0000000000000000 [ 3180.244921] R13: ffff888017480000 R14: ffff888017480000 R15: ffff888017480010 [ 3180.244924] FS:  00007f26e5a526c0(0000) GS:ffff88841fc80000(0000) knlGS:0000000000000000
[ 3180.244924] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3180.244925] CR2: 00007f0104208440 CR3: 000000032af22000 CR4: 00000000003506a0
[ 3180.244926] Call Trace:
[ 3180.244926]  <TASK>
[ 3180.244927]  tcmu_configure_device+0x29f/0x3a0
[ 3180.244933]  target_configure_device+0x8c/0x2f0
[ 3180.244936]  target_dev_enable_store+0x32/0x60
[ 3180.244940]  configfs_write_iter+0xd5/0x140
[ 3180.244944]  vfs_write+0x1ed/0x4f0
[ 3180.244948]  ksys_write+0x70/0xf0
[ 3180.244949]  __x64_sys_write+0x18/0x20
[ 3180.244950]  do_syscall_64+0x3e/0x90
[ 3180.244956]  entry_SYSCALL_64_after_hwframe+0x72/0xdc
[ 3180.244962] RIP: 0033:0x7f26e875611f
[ 3180.244963] Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 39 d5 f8 ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 8c d5 f8 ff 48 [ 3180.244963] RSP: 002b:00007f26e5a51cf0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 [ 3180.244966] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f26e875611f [ 3180.244966] RDX: 0000000000000001 RSI: 00007f26be6549f0 RDI: 0000000000000030 [ 3180.244967] RBP: 00007f26e5a51e20 R08: 0000000000000000 R09: 00000000ffffffff [ 3180.244967] R10: 0000000000000000 R11: 0000000000000293 R12: 00007f26e5a525c0 [ 3180.244968] R13: 00007f26e5cab8a8 R14: 0000000000000001 R15: 0000000000000400
[ 3180.244968]  </TASK>
[ 3180.244969] ---[ end trace 0000000000000000 ]---
[ 3180.244970] RIP: 0010:__list_add_valid+0x94/0xa0
[ 3180.244971] Code: d1 48 89 c6 4c 89 c2 48 c7 c7 38 e1 4b 82 e8 63 25 b3 ff 0f 0b 48 89 f2 48 89 c1 48 89 fe 48 c7 c7 90 e1 4b 82 e8 4c 25 b3 ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90
[ 3180.244972] RSP: 0018:ffffc90002e7fd68 EFLAGS: 00010246
[ 3180.244973] RAX: 0000000000000058 RBX: ffff888017480018 RCX: 0000000000000000 [ 3180.244973] RDX: 0000000000000000 RSI: ffffffff824440d9 RDI: 00000000ffffffff [ 3180.244974] RBP: ffffc90002e7fd68 R08: 0000000000000001 R09: 0000000000000001 [ 3180.244974] R10: 000000001b629664 R11: 0000000000000005 R12: 0000000000000000 [ 3180.244975] R13: ffff888017480000 R14: ffff888017480000 R15: ffff888017480010 [ 3180.244977] FS:  00007f26e5a526c0(0000) GS:ffff88841fc80000(0000) knlGS:0000000000000000
[ 3180.244977] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3180.244978] CR2: 00007f0104208440 CR3: 000000032af22000 CR4: 00000000003506a0
[ 3180.245068] se_dev->se_dev_ptr already set for storage object
[ 3180.245087] kobject: 'uio11' (00000000a5f1af78): fill_kobj_path: path = '/devices/tcm_user/uio/uio11' [ 3180.245265] tcmu nl cmd 1/-2 completion could not find device with dev id 91. [ 3180.245491] kobject: 'maps' (000000009b2a87fb): kobject_add_internal: parent: 'uio11', set: '<NULL>' [ 3180.245749] tcmu nl cmd 1/-2 completion could not find device with dev id 94. [ 3180.245966] kobject: 'map0' (00000000d832f7b9): kobject_add_internal: parent: 'maps', set: '<NULL>' [ 3180.246150] tcmu nl cmd 1/-2 completion could not find device with dev id 94.
[ 3180.246349] kobject: 'map0' (00000000d832f7b9): kobject_uevent_env
[ 3180.246523] tcmu nl cmd 1/-2 completion could not find device with dev id 93. [ 3180.246691] kobject: 'map0' (00000000d832f7b9): kobject_uevent_env: filter function caused the event to drop! [ 3180.246878] tcmu nl cmd 1/0 completion could not find device with dev id 91. [ 3180.263756] tcmu nl cmd 1/-2 completion could not find device with dev id 93.

Best regards,
Grzegorz Uriasz

On 21/05/2023 13:28, Grzegorz Uriasz wrote:
Hi Dmitry,

Thank you for your feedback 😄

On 20/05/2023 10:46, Dmitry Bogdanov wrote:
Hi Grzegorz,

On Sat, May 20, 2023 at 02:26:14AM +0200, Grzegorz Uriasz wrote:
This fixes data corruptions arising from concurrent enabling of a target
devices. When multiple enable calls are made concurrently then it is
possible for the target device to be set up twice which results in a
kernel BUG.
Introduces a per target device mutex for serializing enable requests.
Device enable call is already secured by configfs per-file mutex. That
is actually per device. So Enable procedures are already not executed
simulteniously.
True, I've checked the code in configfs and indeed there is a per file/subsystem mutex.

Look like you wrongly identified the root cause of double list_add.


If you have an evidence that dev->dev_flags could have no DF_CONFIGURED
bit, then it meeans that it (dev_flags) is raced in other
configuration actions (udev_path, vpd_unit_serial, alias).
Bits in dev->dev_flags are written not atomically and if you writes to
enable, alias, udev_path,unit_serial files simulteniously, then some
bits could be lost.

IHMO the best solution is to make dev_flags changes be atomical.

I've tried that using the following patch:
---
 drivers/target/target_core_configfs.c | 12 ++++++------
 drivers/target/target_core_device.c   |  2 +-
 drivers/target/target_core_iblock.c   |  2 +-
 drivers/target/target_core_pscsi.c    |  4 ++--
 drivers/target/target_core_spc.c      |  8 ++++----
 drivers/target/target_core_tpg.c      |  2 +-
 include/target/target_core_backend.h  |  2 +-
 include/target/target_core_base.h     |  4 ++--
 8 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 74b67c346dfe..bdc06f654aa8 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -1621,7 +1621,7 @@ static ssize_t target_wwn_vpd_unit_serial_store(struct config_item *item,
      * it is doing 'the right thing' wrt a world wide unique
      * VPD Unit Serial Number that OS dependent multipath can depend on.
      */
-    if (dev->dev_flags & DF_FIRMWARE_VPD_UNIT_SERIAL) {
+    if (atomic_read(&dev->dev_flags) & DF_FIRMWARE_VPD_UNIT_SERIAL) {
         pr_err("Underlying SCSI device firmware provided VPD"
             " Unit Serial, ignoring request\n");
         return -EOPNOTSUPP;
@@ -1654,7 +1654,7 @@ static ssize_t target_wwn_vpd_unit_serial_store(struct config_item *item,
     snprintf(buf, INQUIRY_VPD_SERIAL_LEN, "%s", page);
     snprintf(dev->t10_wwn.unit_serial, INQUIRY_VPD_SERIAL_LEN,
             "%s", strstrip(buf));
-    dev->dev_flags |= DF_EMULATED_VPD_UNIT_SERIAL;
+    atomic_or(DF_EMULATED_VPD_UNIT_SERIAL, &dev->dev_flags);

     pr_debug("Target_Core_ConfigFS: Set emulated VPD Unit Serial:"
             " %s\n", dev->t10_wwn.unit_serial);
@@ -2263,7 +2263,7 @@ static ssize_t target_dev_alias_show(struct config_item *item, char *page)
 {
     struct se_device *dev = to_device(item);

-    if (!(dev->dev_flags & DF_USING_ALIAS))
+    if (!(atomic_read(&dev->dev_flags) & DF_USING_ALIAS))
         return 0;

     return snprintf(page, PAGE_SIZE, "%s\n", dev->dev_alias);
@@ -2289,7 +2289,7 @@ static ssize_t target_dev_alias_store(struct config_item *item,
     if (dev->dev_alias[read_bytes - 1] == '\n')
         dev->dev_alias[read_bytes - 1] = '\0';

-    dev->dev_flags |= DF_USING_ALIAS;
+    atomic_or(DF_USING_ALIAS, &dev->dev_flags);

     pr_debug("Target_Core_ConfigFS: %s/%s set alias: %s\n",
         config_item_name(&hba->hba_group.cg_item),
@@ -2303,7 +2303,7 @@ static ssize_t target_dev_udev_path_show(struct config_item *item, char *page)
 {
     struct se_device *dev = to_device(item);

-    if (!(dev->dev_flags & DF_USING_UDEV_PATH))
+    if (!(atomic_read(&dev->dev_flags) & DF_USING_UDEV_PATH))
         return 0;

     return snprintf(page, PAGE_SIZE, "%s\n", dev->udev_path);
@@ -2330,7 +2330,7 @@ static ssize_t target_dev_udev_path_store(struct config_item *item,
     if (dev->udev_path[read_bytes - 1] == '\n')
         dev->udev_path[read_bytes - 1] = '\0';

-    dev->dev_flags |= DF_USING_UDEV_PATH;
+    atomic_or(DF_USING_UDEV_PATH, &dev->dev_flags);

     pr_debug("Target_Core_ConfigFS: %s/%s set udev_path: %s\n",
         config_item_name(&hba->hba_group.cg_item),
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 90f3f4926172..5054b647dd0b 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -967,7 +967,7 @@ int target_configure_device(struct se_device *dev)
     hba->dev_count++;
     spin_unlock(&hba->device_lock);

-    dev->dev_flags |= DF_CONFIGURED;
+    atomic_or(DF_CONFIGURED, &dev->dev_flags);

     return 0;

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index cc838ffd1294..38d0d104661d 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -112,7 +112,7 @@ static int iblock_configure_device(struct se_device *dev)
     if (!ib_dev->ibd_readonly)
         mode |= FMODE_WRITE;
     else
-        dev->dev_flags |= DF_READ_ONLY;
+        atomic_or(DF_READ_ONLY, &dev->dev_flags);

     bd = blkdev_get_by_path(ib_dev->ibd_udev_path, mode, ib_dev);
     if (IS_ERR(bd)) {
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index e7425549e39c..36a1ac519f0b 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -201,7 +201,7 @@ pscsi_get_inquiry_vpd_serial(struct scsi_device *sdev, struct t10_wwn *wwn)

     snprintf(&wwn->unit_serial[0], INQUIRY_VPD_SERIAL_LEN, "%s", &buf[4]);

-    wwn->t10_dev->dev_flags |= DF_FIRMWARE_VPD_UNIT_SERIAL;
+    atomic_or(DF_FIRMWARE_VPD_UNIT_SERIAL, &wwn->t10_dev->dev_flags);

     kfree(buf);
     return 0;
@@ -450,7 +450,7 @@ static int pscsi_configure_device(struct se_device *dev)
          * For the newer PHV_VIRTUAL_HOST_ID struct scsi_device
          * reference, we enforce that udev_path has been set
          */
-        if (!(dev->dev_flags & DF_USING_UDEV_PATH)) {
+        if (!(atomic_read(&dev->dev_flags) & DF_USING_UDEV_PATH)) {
             pr_err("pSCSI: udev_path attribute has not"
                 " been set before ENABLE=1\n");
             return -EINVAL;
diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
index 89c0d56294cc..d380d08a2df0 100644
--- a/drivers/target/target_core_spc.c
+++ b/drivers/target/target_core_spc.c
@@ -159,7 +159,7 @@ spc_emulate_evpd_80(struct se_cmd *cmd, unsigned char *buf)
     struct se_device *dev = cmd->se_dev;
     u16 len;

-    if (dev->dev_flags & DF_EMULATED_VPD_UNIT_SERIAL) {
+    if (atomic_read(&dev->dev_flags) & DF_EMULATED_VPD_UNIT_SERIAL) {
         len = sprintf(&buf[4], "%s", dev->t10_wwn.unit_serial);
         len++; /* Extra Byte for NULL Terminator */
         buf[3] = len;
@@ -239,7 +239,7 @@ spc_emulate_evpd_83(struct se_cmd *cmd, unsigned char *buf)
      * /sys/kernel/config/target/core/$HBA/$DEV/wwn/vpd_unit_serial
      * value in order to return the NAA id.
      */
-    if (!(dev->dev_flags & DF_EMULATED_VPD_UNIT_SERIAL))
+    if (!(atomic_read(&dev->dev_flags) & DF_EMULATED_VPD_UNIT_SERIAL))
         goto check_t10_vend_desc;

     /* CODE SET == Binary */
@@ -267,7 +267,7 @@ spc_emulate_evpd_83(struct se_cmd *cmd, unsigned char *buf)
      */
     id_len = 8; /* For Vendor field */

-    if (dev->dev_flags & DF_EMULATED_VPD_UNIT_SERIAL)
+    if (atomic_read(&dev->dev_flags) & DF_EMULATED_VPD_UNIT_SERIAL)
         id_len += sprintf(&buf[off+12], "%s:%s", prod,
                 &dev->t10_wwn.unit_serial[0]);
     buf[off] = 0x2; /* ASCII */
@@ -720,7 +720,7 @@ spc_emulate_evpd_00(struct se_cmd *cmd, unsigned char *buf)
      * Registered Extended LUN WWN has been set via ConfigFS
      * during device creation/restart.
      */
-    if (cmd->se_dev->dev_flags & DF_EMULATED_VPD_UNIT_SERIAL) {
+    if (atomic_read(&cmd->se_dev->dev_flags) & DF_EMULATED_VPD_UNIT_SERIAL) {
         buf[3] = ARRAY_SIZE(evpd_handlers);
         for (p = 0; p < ARRAY_SIZE(evpd_handlers); ++p)
             buf[p + 4] = evpd_handlers[p].page;
diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index c0e429e5ef31..c88dc36db6de 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -656,7 +656,7 @@ int core_tpg_add_lun(
     list_add_tail(&lun->lun_dev_link, &dev->dev_sep_list);
     spin_unlock(&dev->se_port_lock);

-    if (dev->dev_flags & DF_READ_ONLY)
+    if (atomic_read(&dev->dev_flags) & DF_READ_ONLY)
         lun->lun_access_ro = true;
     else
         lun->lun_access_ro = lun_access_ro;
diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
index a3c193df25b3..27c70a69e088 100644
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h
@@ -122,7 +122,7 @@ bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,

 static inline bool target_dev_configured(struct se_device *se_dev)
 {
-    return !!(se_dev->dev_flags & DF_CONFIGURED);
+    return !!(atomic_read(&se_dev->dev_flags) & DF_CONFIGURED);
 }

 #endif /* TARGET_CORE_BACKEND_H */
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 5f8e96f1516f..5794b2360c47 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -792,8 +792,8 @@ struct se_device_queue {

 struct se_device {
     /* Used for SAM Task Attribute ordering */
-    u32            dev_cur_ordered_id;
-    u32            dev_flags;
+    u32         dev_cur_ordered_id;
+    atomic_t    dev_flags;
 #define DF_CONFIGURED                0x00000001
 #define DF_FIRMWARE_VPD_UNIT_SERIAL        0x00000002
 #define DF_EMULATED_VPD_UNIT_SERIAL        0x00000004



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