KASAN: use-after-free Read in ep_open

Status: upstream: reported C repro on 2026/08/14 19:28
Reported-by: syzbot+7264e75089561d6b35df@syzkaller.appspotmail.com
First crash: 4d10h, last: 3d01h
▶ ▼ Similar bugs (2)
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 done 45 5h16m 19d 0/29 upstream: reported C repro on 2026/07/31 01:28
linux-6.6 KASAN: slab-use-after-free Read in ep_open 19 syz, C 4 5d00h 17d 0/2 upstream: reported C repro on 2026/08/01 12:04

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __mutex_lock_common kernel/locking/mutex.c:582 [inline]
BUG: KASAN: use-after-free in __mutex_lock+0xf4/0xae0 kernel/locking/mutex.c:747
Read of size 8 at addr ffff888077560460 by task syz.3.310/4780

CPU: 1 PID: 4780 Comm: syz.3.310 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 __mutex_lock+0xf4/0xae0 kernel/locking/mutex.c:747
 ep_open+0x4a/0x260 drivers/usb/gadget/legacy/inode.c:819
 do_dentry_open+0x7dd/0x10b0 fs/open.c:882
 do_open fs/namei.c:3634 [inline]
 path_openat+0x2674/0x2f10 fs/namei.c:3791
 do_filp_open+0x1ee/0x420 fs/namei.c:3818
 do_sys_openat2+0x14b/0x4f0 fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1347
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f820b79e0d9
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:00007ffd7ca989c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f820ba25fa0 RCX: 00007f820b79e0d9
RDX: 0000000000000002 RSI: 0000200000000600 RDI: ffffffffffffff9c
RBP: 00007f820b835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f820ba25fac R14: 00007f820ba25fa0 R15: 00007f820ba25fa0
 </TASK>

Allocated by task 4776:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 activate_ep_files drivers/usb/gadget/legacy/inode.c:1596 [inline]
 gadgetfs_bind+0x25b/0x820 drivers/usb/gadget/legacy/inode.c:1687
 gadget_bind_driver+0x2af/0x760 drivers/usb/gadget/udc/core.c:1651
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x24a/0xb40 drivers/base/dd.c:638
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:804
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:834
 __driver_attach+0x43d/0x6c0 drivers/base/dd.c:1220
 bus_for_each_dev+0x182/0x1f0 drivers/base/bus.c:303
 bus_add_driver+0x324/0x5d0 drivers/base/bus.c:620
 driver_register+0x32d/0x430 drivers/base/driver.c:246
 usb_gadget_register_driver_owner+0xf5/0x260 drivers/usb/gadget/udc/core.c:1730
 dev_config+0xe45/0x1260 drivers/usb/gadget/legacy/inode.c:1878
 vfs_write+0x2dc/0x9a0 fs/read_write.c:582
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 4776:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xb6/0x200 mm/slub.c:3700
 destroy_ep_files+0x280/0x340 drivers/usb/gadget/legacy/inode.c:1571
 gadgetfs_unbind+0x105/0x2a0 drivers/usb/gadget/legacy/inode.c:1650
 gadget_unbind_driver+0x1bb/0x3d0 drivers/usb/gadget/udc/core.c:1702
 device_remove drivers/base/dd.c:547 [inline]
 __device_release_driver drivers/base/dd.c:1279 [inline]
 device_release_driver_internal+0x47d/0x7c0 drivers/base/dd.c:1305
 driver_detach+0x1ef/0x2d0 drivers/base/dd.c:1368
 bus_remove_driver+0x11c/0x230 drivers/base/bus.c:679
 usb_gadget_unregister_driver+0x4a/0x70 drivers/usb/gadget/udc/core.c:1762
 dev_release+0x82/0x1f0 drivers/usb/gadget/legacy/inode.c:1194
 __fput+0x20a/0x8b0 fs/file_table.c:320
 task_work_run+0x1d0/0x260 kernel/task_work.c:203
 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:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888077560400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 96 bytes inside of
 512-byte region [ffff888077560400, ffff888077560600)

The buggy address belongs to the physical page:
page:ffffea0001dd5800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x77560
head:ffffea0001dd5800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888017441c80
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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4395, tgid 4395 (syz-executor), ts 91073498086, free_ts 88791479158
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560
 prep_new_page mm/page_alloc.c:2567 [inline]
 get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658
 alloc_slab_page+0x5d/0x180 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:1997
 ___slab_alloc+0xbc5/0x1240 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc_node_track_caller+0xa0/0x240 mm/slab_common.c:956
 kmalloc_reserve net/core/skbuff.c:446 [inline]
 __alloc_skb+0x226/0x7d0 net/core/skbuff.c:515
 alloc_skb include/linux/skbuff.h:1303 [inline]
 alloc_uevent_skb+0x7d/0x230 lib/kobject_uevent.c:290
 uevent_net_broadcast_tagged lib/kobject_uevent.c:351 [inline]
 kobject_uevent_net_broadcast+0x17e/0x530 lib/kobject_uevent.c:412
 kobject_uevent_env+0x555/0x890 lib/kobject_uevent.c:608
 rx_queue_add_kobject net/core/net-sysfs.c:1072 [inline]
 net_rx_queue_update_kobjects+0x244/0x4d0 net/core/net-sysfs.c:1112
 register_queue_kobjects net/core/net-sysfs.c:1772 [inline]
 netdev_register_kobject+0x231/0x320 net/core/net-sysfs.c:2017
 register_netdevice+0x133a/0x1b80 net/core/dev.c:10243
 vxcan_newlink+0x553/0x670 drivers/net/can/vxcan.c:244
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1487 [inline]
 free_pcp_prepare mm/page_alloc.c:1537 [inline]
 free_unref_page_prepare+0x8e5/0x9e0 mm/page_alloc.c:3414
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3509
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 kmem_cache_alloc_node+0x1ad/0x310 mm/slub.c:3404
 __alloc_skb+0xf9/0x7d0 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1303 [inline]
 netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
 netlink_sendmsg+0x654/0xbd0 net/netlink/af_netlink.c:1852
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 __sys_sendto+0x497/0x650 net/socket.c:2153
 __do_sys_sendto net/socket.c:2165 [inline]
 __se_sys_sendto net/socket.c:2161 [inline]
 __x64_sys_sendto+0xda/0xf0 net/socket.c:2161
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff888077560300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888077560380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888077560400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff888077560480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888077560500: 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
2026/08/16 03:53 linux-6.1.y e4f7d8be268e 746171ee .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in ep_open
2026/08/14 19:28 linux-6.1.y e4f7d8be268e 6f9b3e89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in ep_open
* Struck through repros no longer work on HEAD.