syzbot


KASAN: slab-use-after-free Read in sk_skb_reason_drop

Status: upstream: reported syz repro on 2024/06/24 15:26
Subsystems: bluetooth
[Documentation on labels]
Reported-by: syzbot+f115fcf7e49b2ebc902d@syzkaller.appspotmail.com
First crash: 112d, last: 57d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly bluetooth report (Jul 2024) 0 (1) 2024/07/11 07:31
[syzbot] [bluetooth?] KASAN: slab-use-after-free Read in sk_skb_reason_drop 2 (5) 2024/06/25 11:58
Last patch testing requests (5)
Created Duration User Patch Repo Result
2024/07/24 07:03 20m retest repro linux-next OK log
2024/07/24 05:56 37m retest repro net-next OK log
2024/07/24 05:56 21m retest repro net-next OK log
2024/06/25 10:40 26m hdanton@sina.com patch https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2ccbdf43d5e7 OK log
2024/06/25 01:30 22m eadavis@qq.com patch https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 84562f9953ec OK log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: slab-use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
BUG: KASAN: slab-use-after-free in refcount_read include/linux/refcount.h:136 [inline]
BUG: KASAN: slab-use-after-free in skb_unref include/linux/skbuff.h:1228 [inline]
BUG: KASAN: slab-use-after-free in __sk_skb_reason_drop net/core/skbuff.c:1196 [inline]
BUG: KASAN: slab-use-after-free in sk_skb_reason_drop+0x44/0x3d0 net/core/skbuff.c:1224
Read of size 4 at addr ffff888018384724 by task syz-executor.0/5194

CPU: 0 PID: 5194 Comm: syz-executor.0 Not tainted 6.10.0-rc4-syzkaller-00875-g568ebdaba637 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
 refcount_read include/linux/refcount.h:136 [inline]
 skb_unref include/linux/skbuff.h:1228 [inline]
 __sk_skb_reason_drop net/core/skbuff.c:1196 [inline]
 sk_skb_reason_drop+0x44/0x3d0 net/core/skbuff.c:1224
 kfree_skb_reason include/linux/skbuff.h:1260 [inline]
 kfree_skb include/linux/skbuff.h:1269 [inline]
 __hci_req_sync+0x631/0x950 net/bluetooth/hci_request.c:184
 hci_req_sync+0xa9/0xd0 net/bluetooth/hci_request.c:206
 hci_dev_cmd+0x4c5/0xa50 net/bluetooth/hci_core.c:787
 sock_do_ioctl+0x158/0x460 net/socket.c:1222
 sock_ioctl+0x629/0x8e0 net/socket.c:1341
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f54dc27ce0b
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007ffd610690f0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f54dc27ce0b
RDX: 00007ffd61069168 RSI: 00000000400448dd RDI: 0000000000000003
RBP: 000055555daad430 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001
 </TASK>

Allocated by task 4489:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:312 [inline]
 __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3941 [inline]
 slab_alloc_node mm/slub.c:4001 [inline]
 kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4008
 skb_clone+0x20c/0x390 net/core/skbuff.c:2054
 hci_send_cmd_sync net/bluetooth/hci_core.c:4123 [inline]
 hci_cmd_work+0x2a2/0x670 net/bluetooth/hci_core.c:4143
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 4489:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
 poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
 __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2196 [inline]
 slab_free mm/slub.c:4437 [inline]
 kmem_cache_free+0x145/0x350 mm/slub.c:4512
 kfree_skb_reason include/linux/skbuff.h:1260 [inline]
 kfree_skb include/linux/skbuff.h:1269 [inline]
 hci_req_sync_complete+0xe8/0x290 net/bluetooth/hci_request.c:109
 hci_event_packet+0xc75/0x1540 net/bluetooth/hci_event.c:7479
 hci_rx_work+0x3e8/0xca0 net/bluetooth/hci_core.c:4074
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

The buggy address belongs to the object at ffff888018384640
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 228 bytes inside of
 freed 240-byte region [ffff888018384640, ffff888018384730)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x18384
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffefff(slab)
raw: 00fff00000000000 ffff888018ae2780 ffffea000072f700 dead000000000004
raw: 0000000000000000 00000000000c000c 00000001ffffefff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 4546, tgid 4546 (udevadm), ts 31919585452, free_ts 31831647028
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1468
 prep_new_page mm/page_alloc.c:1476 [inline]
 get_page_from_freelist+0x2e43/0x2f00 mm/page_alloc.c:3420
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4678
 __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
 alloc_slab_page+0x5f/0x120 mm/slub.c:2265
 allocate_slab+0x5a/0x2f0 mm/slub.c:2428
 new_slab mm/slub.c:2481 [inline]
 ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3667
 __slab_alloc+0x58/0xa0 mm/slub.c:3757
 __slab_alloc_node mm/slub.c:3810 [inline]
 slab_alloc_node mm/slub.c:3989 [inline]
 kmem_cache_alloc_node_noprof+0x1fe/0x320 mm/slub.c:4044
 __alloc_skb+0x1c3/0x440 net/core/skbuff.c:656
 alloc_skb include/linux/skbuff.h:1320 [inline]
 alloc_uevent_skb+0x74/0x230 lib/kobject_uevent.c:289
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast+0x2fd/0x580 lib/kobject_uevent.c:410
 kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:593
 kobject_synth_uevent+0x4ef/0xae0 lib/kobject_uevent.c:207
 uevent_store+0x4b/0x70 drivers/base/bus.c:633
 kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xa72/0xc90 fs/read_write.c:590
page last free pid 4546 tgid 4546 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1088 [inline]
 free_unref_page+0xd22/0xea0 mm/page_alloc.c:2583
 rcu_do_batch kernel/rcu/tree.c:2535 [inline]
 rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2809
 handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
 __do_softirq kernel/softirq.c:588 [inline]
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:649
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

Memory state around the buggy address:
 ffff888018384600: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff888018384680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888018384700: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
                               ^
 ffff888018384780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888018384800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
==================================================================

Crashes (412):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/06/24 17:29 net-next 568ebdaba637 edc5149a .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/06/23 21:09 net-next 84562f9953ec edc5149a .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/06/24 08:16 linux-next f76698bd9a8c edc5149a .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/08/15 11:02 upstream 9d5906799f7d e4bacdaf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/05 08:00 net-next 7829b376f2a9 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/05 06:20 net-next 7829b376f2a9 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/05 03:35 net-next 7829b376f2a9 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/05 02:24 net-next 7829b376f2a9 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/05 00:40 net-next 7829b376f2a9 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 23:35 net-next 7829b376f2a9 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 22:09 net-next 7829b376f2a9 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 20:10 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 18:15 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 17:00 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 15:53 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 14:10 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 12:49 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 11:32 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 09:36 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 08:12 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 06:29 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 04:25 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 03:02 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 01:56 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 00:53 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 23:24 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 22:19 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 21:59 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 20:57 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 19:32 net-next cda91d5b911a f76a75f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 17:03 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 15:55 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 12:31 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 11:06 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 08:34 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 08:20 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 06:37 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 04:55 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 03:53 net-next ac26327635d6 1ecfa2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/03 02:50 net-next ac26327635d6 07f0a0a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/02 22:05 net-next 19e6ad2c7578 07f0a0a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/02 20:36 net-next 19e6ad2c7578 07f0a0a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/02 18:44 net-next 19e6ad2c7578 07f0a0a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/02 17:05 net-next 19e6ad2c7578 07f0a0a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/02 14:33 net-next 19e6ad2c7578 8373af66 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/02 13:28 net-next 19e6ad2c7578 07f0a0a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/02 12:23 net-next 19e6ad2c7578 8373af66 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/06/20 23:01 net-next a6ec08beec9e dac2aa43 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/09 21:59 linux-next 82d01fe6ee52 79d68ada .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in sk_skb_reason_drop
2024/07/04 19:33 net-next e19f67df9ccb 3f2748a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-net-next-test-gce KFENCE: use-after-free in sk_skb_reason_drop
* Struck through repros no longer work on HEAD.