KASAN: use-after-free Read in tty_open

Status: premoderation: reported syz repro on 2026/09/20 09:30
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+53028cb3a8c7e5c6ed80@syzkaller.appspotmail.com
First crash: 49d, last: 49d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/10/25 lts (merge base) f3df4a783bce syz [report] KASAN: use-after-free Read in tty_open
2026/10/25 upstream (ToT) 330517c63aa9 syz [report] KASAN: slab-use-after-free Read in tty_open
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in tty_open serial 19 syz, C done done 8 2419d 2531d 15/29 fixed on 2020/05/10 10:41
android-5-10 KASAN: use-after-free Read in tty_open 19 syz, C 1 54d 80d 0/2 upstream: reported C repro on 2026/08/20 01:24
linux-4.14 KASAN: use-after-free Read in tty_open 19 syz, C done 5 2430d 2532d 1/1 fixed on 2020/04/13 10:52
android-5-15 KASAN: use-after-free Read in tty_open origin:upstream 19 syz 1 87d 87d 0/2 premoderation: reported syz repro on 2026/08/13 02:17
linux-4.19 KASAN: use-after-free Read in tty_open 19 syz, C done 2 2426d 2532d 1/1 fixed on 2020/04/17 06:51
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/10/11 18:41 11m retest repro android14-6.1 report job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: use-after-free in tty_port_kopened include/linux/tty_port.h:228 [inline]
BUG: KASAN: use-after-free in tty_open_by_driver drivers/tty/tty_io.c:2060 [inline]
BUG: KASAN: use-after-free in tty_open+0x82d/0x1040 drivers/tty/tty_io.c:2128
Read of size 8 at addr ffff888113e1e110 by task syz.2.19/412

CPU: 0 PID: 412 Comm: syz.2.19 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 tty_port_kopened include/linux/tty_port.h:228 [inline]
 tty_open_by_driver drivers/tty/tty_io.c:2060 [inline]
 tty_open+0x82d/0x1040 drivers/tty/tty_io.c:2128
 chrdev_open+0x593/0x600 fs/char_dev.c:414
 do_dentry_open+0x885/0x11f0 fs/open.c:884
 vfs_open+0x73/0x80 fs/open.c:1017
 do_open fs/namei.c:3633 [inline]
 path_openat+0x2699/0x2f30 fs/namei.c:3790
 do_filp_open+0x1ee/0x420 fs/namei.c:3817
 do_sys_openat2+0x15e/0x820 fs/open.c:1343
 do_sys_open fs/open.c:1359 [inline]
 __do_sys_openat fs/open.c:1375 [inline]
 __se_sys_openat fs/open.c:1370 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1370
 x64_sys_call+0x783/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:258
 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: 0033:0x7f13f459e159
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:00007f13f5435028 EFLAGS: 00000246
 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f13f4825fa0 RCX: 00007f13f459e159
RDX: 0000000000000002 RSI: 0000200000000800 RDI: ffffffffffffff9c
RBP: 00007f13f463506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f13f4826038 R14: 00007f13f4825fa0 R15: 00007ffe0d3f2ea8
 </TASK>

Allocated by task 408:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:380 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 kmalloc_trace+0x40/0xb0 mm/slab_common.c:1033
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 gs_port_alloc drivers/usb/gadget/function/u_serial.c:1166 [inline]
 gserial_alloc_line_no_console+0x238/0x700 drivers/usb/gadget/function/u_serial.c:1246
 gserial_alloc_line+0x15/0x20 drivers/usb/gadget/function/u_serial.c:1280
 acm_alloc_instance+0x86/0xe0 drivers/usb/gadget/function/f_acm.c:845
 try_get_usb_function_instance drivers/usb/gadget/functions.c:28 [inline]
 usb_get_function_instance+0xf3/0x310 drivers/usb/gadget/functions.c:44
 function_make+0x118/0x360 drivers/usb/gadget/configfs.c:652
 configfs_mkdir+0x518/0x9e0 fs/configfs/dir.c:1329
 vfs_mkdir+0x39c/0x580 fs/namei.c:4113
 do_mkdirat+0x174/0x4d0 fs/namei.c:4138
 __do_sys_mkdirat fs/namei.c:4153 [inline]
 __se_sys_mkdirat fs/namei.c:4151 [inline]
 __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4151
 x64_sys_call+0x73d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:259
 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 408:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:250
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1750 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
 slab_free mm/slub.c:3712 [inline]
 __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728
 kfree+0x6f/0xf0 mm/slab_common.c:990
 gserial_free_port+0x240/0x2d0 drivers/usb/gadget/function/u_serial.c:1210
 gserial_free_line+0x9b/0x1a0 drivers/usb/gadget/function/u_serial.c:1227
 acm_free_instance+0x39/0x60 drivers/usb/gadget/function/f_acm.c:832
 usb_put_function_instance+0x9b/0xc0 drivers/usb/gadget/functions.c:77
 acm_attr_release+0x15/0x20 drivers/usb/gadget/function/f_acm.c:781
 config_item_cleanup fs/configfs/item.c:128 [inline]
 config_item_release fs/configfs/item.c:137 [inline]
 kref_put include/linux/kref.h:65 [inline]
 config_item_put+0x166/0x210 fs/configfs/item.c:149
 configfs_rmdir+0x8c9/0x980 fs/configfs/dir.c:1540
 vfs_rmdir+0x381/0x4f0 fs/namei.c:4198
 do_rmdir+0x261/0x6b0 fs/namei.c:4259
 __do_sys_rmdir fs/namei.c:4278 [inline]
 __se_sys_rmdir fs/namei.c:4276 [inline]
 __x64_sys_rmdir+0x49/0x50 fs/namei.c:4276
 x64_sys_call+0x68e/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:85
 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

The buggy address belongs to the object at ffff888113e1e000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 272 bytes inside of
 1024-byte region [ffff888113e1e000, ffff888113e1e400)

The buggy address belongs to the physical page:
page:ffffea00044f8600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x113e18
head:ffffea00044f8600 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00044f0600 dead000000000002 ffff888100043080
raw: 0000000000000000 0000000000100010 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 302, tgid 302 (sshd-session), ts 27611555710, free_ts 27566324145
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2680
 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587
 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1967 [inline]
 new_slab+0x98/0x3e0 mm/slub.c:2020
 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177
 __slab_alloc+0x5e/0xa0 mm/slub.c:3263
 slab_alloc_node mm/slub.c:3348 [inline]
 __kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423
 __do_kmalloc_node mm/slab_common.c:937 [inline]
 __kmalloc_node_track_caller+0xa1/0x1e0 mm/slab_common.c:958
 kmalloc_reserve net/core/skbuff.c:449 [inline]
 __alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
 alloc_skb_fclone include/linux/skbuff.h:1372 [inline]
 tcp_stream_alloc_skb+0x47/0x360 net/ipv4/tcp.c:871
 tcp_sendmsg_locked+0xcb7/0x39f0 net/ipv4/tcp.c:1334
 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1492
 inet_sendmsg+0xb6/0xd0 net/ipv4/af_inet.c:841
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 sock_write_iter+0x2ea/0x3f0 net/socket.c:1134
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1581 [inline]
 free_pcp_prepare mm/page_alloc.c:1655 [inline]
 free_unref_page_prepare+0x81b/0x820 mm/page_alloc.c:3622
 free_unref_page+0x93/0x530 mm/page_alloc.c:3720
 free_the_page mm/page_alloc.c:863 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:6021
 __free_slab+0xc7/0x1a0 mm/slub.c:2044
 free_slab mm/slub.c:2059 [inline]
 discard_slab mm/slub.c:2065 [inline]
 __unfreeze_partials+0x15a/0x190 mm/slub.c:2614
 put_cpu_partial+0xa9/0x100 mm/slub.c:2690
 __slab_free+0x1c4/0x280 mm/slub.c:3589
 do_slab_free mm/slub.c:3666 [inline]
 ___cache_free+0xbf/0xd0 mm/slub.c:3722
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0xc6/0x140 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x24/0x80 mm/kasan/common.c:311
 kasan_slab_alloc include/linux/kasan.h:202 [inline]
 slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768
 slab_alloc_node mm/slub.c:3382 [inline]
 slab_alloc mm/slub.c:3392 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3399 [inline]
 kmem_cache_alloc+0x166/0x320 mm/slub.c:3408
 getname_flags+0xba/0x510 fs/namei.c:139
 getname+0x19/0x20 fs/namei.c:218
 do_sys_openat2+0xeb/0x820 fs/open.c:1337

Memory state around the buggy address:
 ffff888113e1e000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888113e1e080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888113e1e100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888113e1e180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888113e1e200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/20 09:30 android14-6.1 8cef8b5b11b7 853b104b .config strace log report syz / log [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in tty_open
* Struck through repros no longer work on HEAD.