Hello, When fuzzing the Linux kernel driver v6.0-rc4, the following crash was triggered. HEAD commit: 7e18e42e4b280c85b76967a9106a13ca61c16179 git tree: upstream kernel config: https://pastebin.com/raw/xtrgsXP3 C reproducer: https://pastebin.com/raw/72y5dCXx console output: https://pastebin.com/raw/MDQWXdya Basically, in the c reproducer, we use the gadget module to emulate attaching a USB device(vendor id: 0x2040, product id: 0xc000, with the net function) and executing some simple sequence of system calls. To reproduce this crash, we utilize a third-party library to emulate the attaching process: https://github.com/linux-usb-gadgets/libusbgx. Just clone this repository, install it, and compile the c reproducer with ``` gcc crash.c -lusbgx -lconfig -o crash ``` will do the trick. I would appreciate it if you have any idea how to solve this bug. The crash report is as follows: BUG: KASAN: use-after-free in dummy_timer+0x2aa4/0x33d0 drivers/usb/gadget/udc/dummy_hcd.c:1844 Read of size 4 at addr ffff88802a558274 by task syz-fuzzer/6413 CPU: 0 PID: 6413 Comm: syz-fuzzer Not tainted 6.0.0-rc4+ #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline] print_report.cold+0xe5/0x66d mm/kasan/report.c:433 kasan_report+0x8a/0x1b0 mm/kasan/report.c:495 dummy_timer+0x2aa4/0x33d0 drivers/usb/gadget/udc/dummy_hcd.c:1844 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x69c/0xad0 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb6/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d0/0x908 kernel/softirq.c:571 invoke_softirq kernel/softirq.c:445 [inline] __irq_exit_rcu kernel/softirq.c:650 [inline] irq_exit_rcu+0xf2/0x130 kernel/softirq.c:662 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1106 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649 RIP: 0010:tomoyo_check_path_acl security/tomoyo/file.c:260 [inline] RIP: 0010:tomoyo_check_path_acl+0xbe/0x150 security/tomoyo/file.c:252 Code: 31 ed d3 fb 83 e3 01 89 de e8 fe 85 c1 fd 85 db 75 13 e8 95 84 c1 fd 44 89 e8 48 83 c4 08 5b 5d 41 5c 41 5d c3 e8 82 84 c1 fd <48> 8d 7d 18 48 b8 00 00 00 00 00 fc ff df 49 8d 74 24 20 48 89 fa RSP: 0018:ffffc9000226f978 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff888041f9ba80 RDX: 0000000000000000 RSI: ffff888041f9ba80 RDI: 0000000000000002 RBP: ffffc9000226fad0 R08: ffffffff83b963ae R09: 0000000000000000 R10: 0000000000000005 R11: fffffbfff1d34742 R12: ffff8880484ab900 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 tomoyo_check_acl+0x13c/0x440 security/tomoyo/domain.c:175 tomoyo_path_permission security/tomoyo/file.c:586 [inline] tomoyo_path_permission+0x1ff/0x3a0 security/tomoyo/file.c:573 tomoyo_path_perm+0x2fc/0x420 security/tomoyo/file.c:838 security_inode_getattr+0xcf/0x140 security/security.c:1345 vfs_getattr+0x22/0x60 fs/stat.c:157 vfs_statx+0x170/0x360 fs/stat.c:232 vfs_fstatat+0x8c/0xb0 fs/stat.c:255 __do_sys_newfstatat+0x91/0x110 fs/stat.c:425 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x49d60a Code: e8 1b 98 fc ff 48 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 4c 8b 54 24 28 4c 8b 44 24 30 4c 8b 4c 24 38 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 40 ff ff ff ff 48 c7 44 24 48 RSP: 002b:000000c002c25d20 EFLAGS: 00000206 ORIG_RAX: 0000000000000106 RAX: ffffffffffffffda RBX: 000000c000022500 RCX: 000000000049d60a RDX: 000000c001a98928 RSI: 000000c0019e92b0 RDI: ffffffffffffff9c RBP: 000000c002c25db0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000100 R11: 0000000000000206 R12: 0000000000000000 R13: 0000000000000000 R14: 000000c002f6b860 R15: 000000000000012b </TASK> Allocated by task 2959: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 kasan_set_track mm/kasan/common.c:45 [inline] set_alloc_info mm/kasan/common.c:437 [inline] ____kasan_kmalloc mm/kasan/common.c:516 [inline] ____kasan_kmalloc mm/kasan/common.c:475 [inline] __kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:525 kasan_kmalloc include/linux/kasan.h:234 [inline] kmem_cache_alloc_trace+0x19b/0x380 mm/slub.c:3284 kmalloc include/linux/slab.h:600 [inline] kzalloc include/linux/slab.h:733 [inline] smsusb_init_device+0xb2/0xaf8 drivers/media/usb/siano/smsusb.c:395 smsusb_probe+0xd42/0xddf drivers/media/usb/siano/smsusb.c:566 usb_probe_interface+0x361/0x800 drivers/usb/core/driver.c:396 call_driver_probe drivers/base/dd.c:560 [inline] really_probe+0x249/0xa90 drivers/base/dd.c:639 __driver_probe_device+0x1df/0x4d0 drivers/base/dd.c:778 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:808 __device_attach_driver+0x1da/0x2d0 drivers/base/dd.c:936 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:427 __device_attach+0x283/0x480 drivers/base/dd.c:1008 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:487 device_add+0xc96/0x1da0 drivers/base/core.c:3517 usb_set_configuration+0x1014/0x1900 drivers/usb/core/message.c:2170 usb_generic_driver_probe+0x9d/0xe0 drivers/usb/core/generic.c:238 usb_probe_device+0xd4/0x2a0 drivers/usb/core/driver.c:293 call_driver_probe drivers/base/dd.c:560 [inline] really_probe+0x249/0xa90 drivers/base/dd.c:639 __driver_probe_device+0x1df/0x4d0 drivers/base/dd.c:778 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:808 __device_attach_driver+0x1da/0x2d0 drivers/base/dd.c:936 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:427 __device_attach+0x283/0x480 drivers/base/dd.c:1008 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:487 device_add+0xc96/0x1da0 drivers/base/core.c:3517 usb_new_device.cold+0x69d/0x10ef drivers/usb/core/hub.c:2573 hub_port_connect drivers/usb/core/hub.c:5353 [inline] hub_port_connect_change drivers/usb/core/hub.c:5497 [inline] port_event drivers/usb/core/hub.c:5653 [inline] hub_event+0x23bd/0x4260 drivers/usb/core/hub.c:5735 process_one_work+0x9c7/0x1650 kernel/workqueue.c:2289 worker_thread+0x623/0x1070 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 Freed by task 2959: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 kasan_set_track+0x21/0x30 mm/kasan/common.c:45 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370 ____kasan_slab_free mm/kasan/common.c:367 [inline] ____kasan_slab_free mm/kasan/common.c:329 [inline] __kasan_slab_free+0x11d/0x1b0 mm/kasan/common.c:375 kasan_slab_free include/linux/kasan.h:200 [inline] slab_free_hook mm/slub.c:1754 [inline] slab_free_freelist_hook mm/slub.c:1780 [inline] slab_free mm/slub.c:3534 [inline] kfree+0xe9/0x650 mm/slub.c:4562 smsusb_term_device+0xd1/0x160 drivers/media/usb/siano/smsusb.c:350 smsusb_init_device+0xa76/0xaf8 drivers/media/usb/siano/smsusb.c:487 smsusb_probe+0xd42/0xddf drivers/media/usb/siano/smsusb.c:566 usb_probe_interface+0x361/0x800 drivers/usb/core/driver.c:396 call_driver_probe drivers/base/dd.c:560 [inline] really_probe+0x249/0xa90 drivers/base/dd.c:639 __driver_probe_device+0x1df/0x4d0 drivers/base/dd.c:778 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:808 __device_attach_driver+0x1da/0x2d0 drivers/base/dd.c:936 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:427 __device_attach+0x283/0x480 drivers/base/dd.c:1008 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:487 device_add+0xc96/0x1da0 drivers/base/core.c:3517 usb_set_configuration+0x1014/0x1900 drivers/usb/core/message.c:2170 usb_generic_driver_probe+0x9d/0xe0 drivers/usb/core/generic.c:238 usb_probe_device+0xd4/0x2a0 drivers/usb/core/driver.c:293 call_driver_probe drivers/base/dd.c:560 [inline] really_probe+0x249/0xa90 drivers/base/dd.c:639 __driver_probe_device+0x1df/0x4d0 drivers/base/dd.c:778 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:808 __device_attach_driver+0x1da/0x2d0 drivers/base/dd.c:936 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:427 __device_attach+0x283/0x480 drivers/base/dd.c:1008 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:487 device_add+0xc96/0x1da0 drivers/base/core.c:3517 usb_new_device.cold+0x69d/0x10ef drivers/usb/core/hub.c:2573 hub_port_connect drivers/usb/core/hub.c:5353 [inline] hub_port_connect_change drivers/usb/core/hub.c:5497 [inline] port_event drivers/usb/core/hub.c:5653 [inline] hub_event+0x23bd/0x4260 drivers/usb/core/hub.c:5735 process_one_work+0x9c7/0x1650 kernel/workqueue.c:2289 worker_thread+0x623/0x1070 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 Last potentially related work creation: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 __kasan_record_aux_stack+0xbe/0xd0 mm/kasan/generic.c:348 insert_work+0x4a/0x390 kernel/workqueue.c:1358 __queue_work+0x4d4/0x1200 kernel/workqueue.c:1517 queue_work_on+0xee/0x110 kernel/workqueue.c:1545 queue_work include/linux/workqueue.h:503 [inline] schedule_work include/linux/workqueue.h:564 [inline] smsusb_onresponse+0x58f/0x780 drivers/media/usb/siano/smsusb.c:147 __usb_hcd_giveback_urb+0x2c2/0x5a0 drivers/usb/core/hcd.c:1671 usb_hcd_giveback_urb+0x380/0x430 drivers/usb/core/hcd.c:1754 dummy_timer+0x1263/0x33d0 drivers/usb/gadget/udc/dummy_hcd.c:1988 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x69c/0xad0 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb6/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d0/0x908 kernel/softirq.c:571 Second to last potentially related work creation: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 __kasan_record_aux_stack+0xbe/0xd0 mm/kasan/generic.c:348 insert_work+0x4a/0x390 kernel/workqueue.c:1358 __queue_work+0x4d4/0x1200 kernel/workqueue.c:1517 queue_work_on+0xee/0x110 kernel/workqueue.c:1545 queue_work include/linux/workqueue.h:503 [inline] schedule_work include/linux/workqueue.h:564 [inline] smsusb_onresponse+0x58f/0x780 drivers/media/usb/siano/smsusb.c:147 __usb_hcd_giveback_urb+0x2c2/0x5a0 drivers/usb/core/hcd.c:1671 usb_hcd_giveback_urb+0x380/0x430 drivers/usb/core/hcd.c:1754 dummy_timer+0x1263/0x33d0 drivers/usb/gadget/udc/dummy_hcd.c:1988 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x69c/0xad0 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb6/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d0/0x908 kernel/softirq.c:571 The buggy address belongs to the object at ffff88802a558000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 628 bytes inside of 4096-byte region [ffff88802a558000, ffff88802a559000) The buggy address belongs to the physical page: page:ffffea0000a95600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a558 head:ffffea0000a95600 order:3 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888011c42140 raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 150, tgid 150 (kworker/0:2), ts 346929849238, free_ts 346865690650 set_page_owner include/linux/page_owner.h:31 [inline] post_alloc_hook mm/page_alloc.c:2525 [inline] prep_new_page+0x2c6/0x350 mm/page_alloc.c:2532 get_page_from_freelist+0xae9/0x3a80 mm/page_alloc.c:4283 __alloc_pages+0x321/0x710 mm/page_alloc.c:5515 alloc_pages+0x117/0x2f0 mm/mempolicy.c:2270 alloc_slab_page mm/slub.c:1824 [inline] allocate_slab mm/slub.c:1969 [inline] new_slab+0x246/0x3a0 mm/slub.c:2029 ___slab_alloc+0xa50/0x1060 mm/slub.c:3031 __slab_alloc.isra.0+0x4d/0xa0 mm/slub.c:3118 slab_alloc_node mm/slub.c:3209 [inline] __kmalloc_node_track_caller+0x2ec/0x370 mm/slub.c:4955 kmalloc_reserve+0x32/0xd0 net/core/skbuff.c:358 __alloc_skb+0x11a/0x320 net/core/skbuff.c:430 alloc_skb include/linux/skbuff.h:1257 [inline] nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:742 [inline] nsim_dev_trap_report drivers/net/netdevsim/dev.c:799 [inline] nsim_dev_trap_report_work+0x2ba/0xc40 drivers/net/netdevsim/dev.c:844 process_one_work+0x9c7/0x1650 kernel/workqueue.c:2289 worker_thread+0x623/0x1070 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1449 [inline] free_pcp_prepare+0x5ab/0xd00 mm/page_alloc.c:1499 free_unref_page_prepare mm/page_alloc.c:3380 [inline] free_unref_page+0x19/0x410 mm/page_alloc.c:3476 __unfreeze_partials+0x3f3/0x410 mm/slub.c:2548 qlink_free mm/kasan/quarantine.c:168 [inline] qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187 kasan_quarantine_reduce+0x13d/0x180 mm/kasan/quarantine.c:294 __kasan_slab_alloc+0xa2/0xc0 mm/kasan/common.c:447 kasan_slab_alloc include/linux/kasan.h:224 [inline] slab_post_alloc_hook+0x4d/0x4f0 mm/slab.h:727 slab_alloc_node mm/slub.c:3243 [inline] slab_alloc mm/slub.c:3251 [inline] __kmem_cache_alloc_lru mm/slub.c:3258 [inline] kmem_cache_alloc+0x151/0x360 mm/slub.c:3268 getname_flags fs/namei.c:139 [inline] getname_flags+0xd2/0x5b0 fs/namei.c:129 vfs_fstatat+0x73/0xb0 fs/stat.c:254 vfs_stat include/linux/fs.h:3278 [inline] __do_sys_newstat+0x88/0x110 fs/stat.c:398 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Memory state around the buggy address: ffff88802a558100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88802a558180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88802a558200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88802a558280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88802a558300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ---------------- Code disassembly (best guess): 0: 31 ed xor %ebp,%ebp 2: d3 fb sar %cl,%ebx 4: 83 e3 01 and $0x1,%ebx 7: 89 de mov %ebx,%esi 9: e8 fe 85 c1 fd callq 0xfdc1860c e: 85 db test %ebx,%ebx 10: 75 13 jne 0x25 12: e8 95 84 c1 fd callq 0xfdc184ac 17: 44 89 e8 mov %r13d,%eax 1a: 48 83 c4 08 add $0x8,%rsp 1e: 5b pop %rbx 1f: 5d pop %rbp 20: 41 5c pop %r12 22: 41 5d pop %r13 24: c3 retq 25: e8 82 84 c1 fd callq 0xfdc184ac * 2a: 48 8d 7d 18 lea 0x18(%rbp),%rdi <-- trapping instruction 2e: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 35: fc ff df 38: 49 8d 74 24 20 lea 0x20(%r12),%rsi 3d: 48 89 fa mov %rdi,%rdx
