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

Status: upstream: reported C repro on 2026/08/01 12:04
Reported-by: syzbot+6e21a0f7fbd3594567a3@syzkaller.appspotmail.com
First crash: 55d, last: 18h00m
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in ep_open prio:normal usb 19 syz, C done 179 10h14m 56d 0/29 upstream: reported C repro on 2026/07/31 01:28
linux-6.1 KASAN: use-after-free Read in ep_open origin:upstream 19 syz, C 15 1d05h 41d 0/3 upstream: reported C repro on 2026/08/14 19:28
linux-5.15 KASAN: use-after-free Read in ep_open origin:upstream 19 syz, C 7 18d 33d 0/3 upstream: reported C repro on 2026/08/23 02:59

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 ffff8880301ed460 by task syz.0.146/6116

CPU: 1 PID: 6116 Comm: syz.0.146 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:3683 [inline]
 path_openat+0x284f/0x3270 fs/namei.c:3844
 do_filp_open+0x1f2/0x430 fs/namei.c:3871
 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: 0033:0x7fe60079e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc0a40ecc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fe600a25fa0 RCX: 00007fe60079e0d9
RDX: 0000000000000002 RSI: 0000200000000600 RDI: ffffffffffffff9c
RBP: 00007fe600835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe600a25fac R14: 00007fe600a25fa0 R15: 00007fe600a25fa0
 </TASK>

Allocated by task 6115:
 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 6115:
 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
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 kvfree_call_rcu+0xee/0x780 kernel/rcu/tree.c:3452
 ipv6_mc_destroy_dev+0x3bf/0x590 net/ipv6/mcast.c:2847
 addrconf_ifdown+0x13b8/0x18a0 net/ipv6/addrconf.c:3998
 addrconf_notify+0x6c6/0x1010 net/ipv6/addrconf.c:-1
 notifier_call_chain+0x18f/0x380 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2077 [inline]
 call_netdevice_notifiers net/core/dev.c:2091 [inline]
 unregister_netdevice_many_notify+0x1037/0x1910 net/core/dev.c:11124
 unregister_netdevice_many net/core/dev.c:11180 [inline]
 default_device_exit_batch+0x962/0xa00 net/core/dev.c:11746
 ops_exit_list net/core/net_namespace.c:178 [inline]
 cleanup_net+0x792/0xbb0 net/core/net_namespace.c:652
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 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

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 kvfree_call_rcu+0xee/0x780 kernel/rcu/tree.c:3452
 ep_eventpoll_release+0x48/0x60 fs/eventpoll.c:876
 __fput+0x221/0x940 fs/file_table.c:418
 __do_sys_close fs/open.c:1574 [inline]
 __se_sys_close+0x15c/0x1e0 fs/open.c:1559
 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

The buggy address belongs to the object at ffff8880301ed400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 96 bytes inside of
 freed 512-byte region [ffff8880301ed400, ffff8880301ed600)

The buggy address belongs to the physical page:
page:ffffea0000c07b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x301ec
head:ffffea0000c07b00 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 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4401, tgid 4401 (kworker/u4:7), ts 26017405914, free_ts 0
 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]
 alloc_bprm+0x56/0x9a0 fs/exec.c:1538
 kernel_execve+0x98/0x980 fs/exec.c:2023
 call_usermodehelper_exec_async+0x20b/0x350 kernel/umh.c:110
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880301ed300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880301ed380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880301ed400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff8880301ed480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880301ed500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (20):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/08 21:05 linux-6.6.y 6436c12a2ced 5d63f80b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
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
2026/09/24 20:08 linux-6.6.y 79643295eba1 3c3cdf19 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/17 10:47 linux-6.6.y 79643295eba1 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 18:52 linux-6.6.y 79643295eba1 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 11:21 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 11:05 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 09:42 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 09:28 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 09:27 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 09:27 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/14 09:21 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/13 15:27 linux-6.6.y 8b73de7da85f 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/09/02 11:44 linux-6.6.y a4a971135a2f 587f6b29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/08/23 04:34 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/08/23 04:33 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/08/23 04:29 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/08/23 04:24 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ep_open
2026/08/14 04:45 linux-6.6.y d27334b2888c b13552fe .config console log report info [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.