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/NeCr7cX0 console output: https://pastebin.com/raw/4uH5CL2k Basically, in the c reproducer, we use the gadget module to emulate attaching a USB device(vendor id: 0x5ac, product id: 0x30a) 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 f_hidg_read+0xa7a/0xe20 drivers/usb/gadget/function/f_hid.c:399 Read of size 1 at addr ffff888027a49012 by task syz-executor.2/7951 CPU: 1 PID: 7951 Comm: syz-executor.2 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: <TASK> __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 f_hidg_read+0xa7a/0xe20 drivers/usb/gadget/function/f_hid.c:399 vfs_read+0x257/0x940 fs/read_write.c:468 ksys_read+0x127/0x250 fs/read_write.c:607 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: 0033:0x7fe3038a80fd Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fe303f02bf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007fe30399c340 RCX: 00007fe3038a80fd RDX: 0000000000002020 RSI: 0000000020000a00 RDI: 0000000000000003 RBP: 00007fe30390b606 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe7356189f R14: 00007ffe73561a40 R15: 00007fe303f02d80 </TASK> Allocated by task 7828: 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] hidg_alloc+0x49/0x620 drivers/usb/gadget/function/f_hid.c:1271 usb_get_function+0x54/0xc0 drivers/usb/gadget/functions.c:61 config_usb_cfg_link+0x1bf/0x3b0 drivers/usb/gadget/configfs.c:461 configfs_symlink+0x542/0x1100 fs/configfs/symlink.c:202 vfs_symlink fs/namei.c:4378 [inline] vfs_symlink+0x579/0x8b0 fs/namei.c:4363 do_symlinkat+0x225/0x2a0 fs/namei.c:4407 __do_sys_symlink fs/namei.c:4429 [inline] __se_sys_symlink fs/namei.c:4427 [inline] __x64_sys_symlink+0x75/0x90 fs/namei.c:4427 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 Freed by task 7952: 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 hidg_free+0x9c/0x110 drivers/usb/gadget/function/f_hid.c:1249 usb_put_function+0x34/0x50 drivers/usb/gadget/functions.c:87 config_usb_cfg_unlink+0x281/0x360 drivers/usb/gadget/configfs.c:500 configfs_unlink+0x3e2/0x830 fs/configfs/symlink.c:250 vfs_unlink+0x343/0x940 fs/namei.c:4229 do_unlinkat+0x3d5/0x660 fs/namei.c:4297 __do_sys_unlink fs/namei.c:4345 [inline] __se_sys_unlink fs/namei.c:4343 [inline] __x64_sys_unlink+0x3e/0x50 fs/namei.c:4343 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 The buggy address belongs to the object at ffff888027a49000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 18 bytes inside of 1024-byte region [ffff888027a49000, ffff888027a49400) The buggy address belongs to the physical page: page:ffffea00009e9200 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888027a4d800 pfn:0x27a48 head:ffffea00009e9200 order:3 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 ffffea00009e5c08 ffffea0000ab0008 ffff888011c41dc0 raw: ffff888027a4d800 000000000010000d 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6450, tgid 6450 (syz-executor.0), ts 172570752202, free_ts 168197901202 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+0x2ed/0x360 mm/slub.c:4468 kmalloc_node include/linux/slab.h:623 [inline] kzalloc_node include/linux/slab.h:744 [inline] qdisc_alloc+0xb9/0xc30 net/sched/sch_generic.c:938 qdisc_create_dflt+0x71/0x4a0 net/sched/sch_generic.c:997 attach_one_default_qdisc.constprop.0+0xc4/0x1a0 net/sched/sch_generic.c:1152 netdev_for_each_tx_queue include/linux/netdevice.h:2437 [inline] attach_default_qdiscs net/sched/sch_generic.c:1170 [inline] dev_activate+0x5a7/0xa10 net/sched/sch_generic.c:1229 __dev_open+0x32d/0x460 net/core/dev.c:1441 __dev_change_flags+0x500/0x650 net/core/dev.c:8556 dev_change_flags+0x93/0x170 net/core/dev.c:8627 do_setlink+0xacc/0x3ca0 net/core/rtnetlink.c:2780 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 release_pages+0x386/0x16c0 mm/swap.c:978 tlb_batch_pages_flush mm/mmu_gather.c:58 [inline] tlb_flush_mmu_free mm/mmu_gather.c:255 [inline] tlb_flush_mmu+0xef/0x690 mm/mmu_gather.c:262 tlb_finish_mmu+0x93/0x3c0 mm/mmu_gather.c:353 unmap_region+0x27f/0x350 mm/mmap.c:2625 __do_munmap+0xafe/0x10c0 mm/mmap.c:2836 __vm_munmap+0xf7/0x230 mm/mmap.c:2859 __do_sys_munmap mm/mmap.c:2884 [inline] __se_sys_munmap mm/mmap.c:2881 [inline] __x64_sys_munmap+0x55/0x80 mm/mmap.c:2881 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: ffff888027a48f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888027a48f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888027a49000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888027a49080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888027a49100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
