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

Status: upstream: reported syz repro on 2026/08/01 12:04
Reported-by: syzbot+6e21a0f7fbd3594567a3@syzkaller.appspotmail.com
First crash: 2d14h, last: 2d04h
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in ep_open usb prio:normal 19 syz, C 19 5h22m 4d00h 0/29 upstream: reported C repro on 2026/07/31 01:28

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in __mutex_lock_common kernel/locking/mutex.c:582 [inline]
BUG: KASAN: slab-use-after-free in __mutex_lock+0xfc/0xc80 kernel/locking/mutex.c:747
Read of size 8 at addr ffff888023afa460 by task syz-executor/5890

CPU: 0 PID: 5890 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 __mutex_lock+0xfc/0xc80 kernel/locking/mutex.c:747
 ep_open+0x4e/0x270 drivers/usb/gadget/legacy/inode.c:819
 do_dentry_open+0x880/0x14b0 fs/open.c:929
 do_open fs/namei.c:3640 [inline]
 path_openat+0x284f/0x3270 fs/namei.c:3801
 do_filp_open+0x1f2/0x430 fs/namei.c:3828
 do_sys_openat2+0x134/0x1d0 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6938f5e84e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffdddeeb688 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000055557e0e0500 RCX: 00007f6938f5e84e
RDX: 0000000000000000 RSI: 00007ffdddeeb7f0 RDI: ffffffffffffff9c
RBP: 00007ffdddeeb7f0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffdddeec8e0
R13: 00007f693903445c R14: 000055557e0e04e8 R15: 0000000000000006
 </TASK>

Allocated by task 5932:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 activate_ep_files drivers/usb/gadget/legacy/inode.c:1596 [inline]
 gadgetfs_bind+0x25f/0x830 drivers/usb/gadget/legacy/inode.c:1687
 gadget_bind_driver+0x2b3/0x770 drivers/usb/gadget/udc/core.c:1651
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x247/0xae0 drivers/base/dd.c:717
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:879
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:909
 __driver_attach+0x444/0x6d0 drivers/base/dd.c:1295
 bus_for_each_dev+0x235/0x2b0 drivers/base/bus.c:370
 bus_add_driver+0x340/0x630 drivers/base/bus.c:723
 driver_register+0x23a/0x310 drivers/base/driver.c:246
 usb_gadget_register_driver_owner+0xf9/0x270 drivers/usb/gadget/udc/core.c:1730
 dev_config+0xe49/0x1260 drivers/usb/gadget/legacy/inode.c:1878
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 173:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 destroy_ep_files+0x280/0x340 drivers/usb/gadget/legacy/inode.c:1571
 gadgetfs_unbind+0x109/0x2b0 drivers/usb/gadget/legacy/inode.c:1650
 gadget_unbind_driver+0x1bf/0x3e0 drivers/usb/gadget/udc/core.c:1702
 device_remove drivers/base/dd.c:626 [inline]
 __device_release_driver drivers/base/dd.c:1351 [inline]
 device_release_driver_internal+0x408/0x6f0 drivers/base/dd.c:1374
 driver_detach+0x1f3/0x2d0 drivers/base/dd.c:1437
 bus_remove_driver+0x221/0x2f0 drivers/base/bus.c:792
 usb_gadget_unregister_driver+0x4e/0x70 drivers/usb/gadget/udc/core.c:1762
 dev_release+0x86/0x200 drivers/usb/gadget/legacy/inode.c:1194
 __fput+0x221/0x940 fs/file_table.c:418
 delayed_fput+0x58/0x80 fs/file_table.c:441
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff888023afa400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 96 bytes inside of
 freed 512-byte region [ffff888023afa400, ffff888023afa600)

The buggy address belongs to the physical page:
page:ffffea00008ebe00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x23af8
head:ffffea00008ebe00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c41c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5932, tgid 5931 (syz.0.17), ts 102512897312, free_ts 102501796454
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_slab_page+0x5d/0x180 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 activate_ep_files drivers/usb/gadget/legacy/inode.c:1596 [inline]
 gadgetfs_bind+0x25f/0x830 drivers/usb/gadget/legacy/inode.c:1687
 gadget_bind_driver+0x2b3/0x770 drivers/usb/gadget/udc/core.c:1651
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x247/0xae0 drivers/base/dd.c:717
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:879
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:909
 __driver_attach+0x444/0x6d0 drivers/base/dd.c:1295
 bus_for_each_dev+0x235/0x2b0 drivers/base/bus.c:370
 bus_add_driver+0x340/0x630 drivers/base/bus.c:723
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x319/0x400 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x17e/0x2c0 mm/slub.c:3519
 getname_flags+0xbb/0x500 fs/namei.c:140
 vfs_fstatat+0x111/0x1b0 fs/stat.c:298
 __do_sys_newfstatat fs/stat.c:463 [inline]
 __se_sys_newfstatat fs/stat.c:457 [inline]
 __x64_sys_newfstatat+0x149/0x1f0 fs/stat.c:457
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff888023afa300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888023afa380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888023afa400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff888023afa480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888023afa500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/01 21:39 linux-6.6.y a1153c0deb44 e611ffe1 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/08/01 12:04 linux-6.6.y a1153c0deb44 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
* Struck through repros no longer work on HEAD.