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KASAN: slab-out-of-bounds Write in do_con_write (3)

Status: upstream: reported on 2026/02/26 08:31
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+8e9c1abac3ceb45abffe@syzkaller.appspotmail.com
First crash: 118d, last: 6h08m
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[syzbot] Monthly serial report (May 2026) 0 (1) 2026/05/02 20:32
[syzbot] Monthly serial report (Apr 2026) 0 (1) 2026/04/01 13:14
[syzbot] Monthly serial report (Mar 2026) 0 (1) 2026/03/03 08:07
[syzbot] [serial?] KASAN: slab-out-of-bounds Write in do_con_write (3) 0 (1) 2026/02/26 08:31
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Write in do_con_write (2) serial 21 6 238d 242d 0/29 auto-obsoleted due to no activity on 2025/12/19 08:09
upstream KASAN: slab-out-of-bounds Write in do_con_write serial 21 4 374d 452d 0/29 auto-obsoleted due to no activity on 2025/08/04 16:13

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in vc_con_write_normal drivers/tty/vt/vt.c:3237 [inline]
BUG: KASAN: slab-out-of-bounds in do_con_write+0x3a8d/0x4a10 drivers/tty/vt/vt.c:3328
Write of size 2 at addr ffff8880560d9a60 by task syz.0.585/8376

CPU: 0 UID: 0 PID: 8376 Comm: syz.0.585 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
 vc_con_write_normal drivers/tty/vt/vt.c:3237 [inline]
 do_con_write+0x3a8d/0x4a10 drivers/tty/vt/vt.c:3328
 con_write+0x23/0xb0 drivers/tty/vt/vt.c:3660
 process_output_block drivers/tty/n_tty.c:557 [inline]
 n_tty_write+0x431/0x11c0 drivers/tty/n_tty.c:2366
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write.isra.0+0x4d2/0x890 drivers/tty/tty_io.c:1081
 tty_write drivers/tty/tty_io.c:1102 [inline]
 redirected_tty_write drivers/tty/tty_io.c:1125 [inline]
 redirected_tty_write+0xd4/0x120 drivers/tty/tty_io.c:1105
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f075019cdd9
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:00007f0750fc4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f0750415fa0 RCX: 00007f075019cdd9
RDX: 000000000000fdef RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007f0750232d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0750416038 R14: 00007f0750415fa0 R15: 00007ffe8bf93bf8
 </TASK>

Allocated by task 4992:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5295 [inline]
 __kmalloc_noprof+0x301/0x850 mm/slub.c:5307
 kmalloc_noprof include/linux/slab.h:954 [inline]
 tomoyo_realpath_from_path+0xb6/0x690 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x276/0x460 security/tomoyo/file.c:827
 security_inode_getattr+0x116/0x280 security/security.c:1895
 vfs_getattr fs/stat.c:259 [inline]
 vfs_fstat+0x4b/0xe0 fs/stat.c:281
 __do_sys_newfstat+0x8b/0x110 fs/stat.c:551
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 4992:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6250 [inline]
 kfree+0x223/0x6c0 mm/slub.c:6565
 tomoyo_realpath_from_path+0x19c/0x690 security/tomoyo/realpath.c:286
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x276/0x460 security/tomoyo/file.c:827
 security_inode_getattr+0x116/0x280 security/security.c:1895
 vfs_getattr fs/stat.c:259 [inline]
 vfs_fstat+0x4b/0xe0 fs/stat.c:281
 __do_sys_newfstat+0x8b/0x110 fs/stat.c:551
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880560d8000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 2656 bytes to the right of
 allocated 4096-byte region [ffff8880560d8000, ffff8880560d9000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x560d8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813fe2f140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe2f140 dead000000000100 dead000000000122
head: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 36, tgid 36 (kworker/u8:2), ts 169630731316, free_ts 169561923157
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7255
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __do_kmalloc_node mm/slub.c:5294 [inline]
 __kmalloc_node_track_caller_noprof+0x694/0x850 mm/slub.c:5407
 kmalloc_reserve+0xe8/0x350 net/core/skbuff.c:635
 __alloc_skb+0x185/0x710 net/core/skbuff.c:713
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:819 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
 nsim_dev_trap_report_work+0x2af/0xd20 drivers/net/netdevsim/dev.c:922
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
 process_scheduled_works kernel/workqueue.c:3385 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 0 tgid 0 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
 __folio_put+0x3b4/0x5f0 mm/swap.c:112
 folio_put include/linux/mm.h:2090 [inline]
 put_page include/linux/mm.h:2159 [inline]
 put_netmem include/net/netmem.h:409 [inline]
 skb_page_unref include/linux/skbuff_ref.h:43 [inline]
 __skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
 skb_release_data+0x649/0x8e0 net/core/skbuff.c:1108
 skb_release_all net/core/skbuff.c:1189 [inline]
 __kfree_skb+0x4f/0x70 net/core/skbuff.c:1203
 tcp_wmem_free_skb include/net/tcp.h:336 [inline]
 tcp_rtx_queue_unlink_and_free include/net/tcp.h:2343 [inline]
 tcp_clean_rtx_queue net/ipv4/tcp_input.c:3698 [inline]
 tcp_ack+0x2086/0x7670 net/ipv4/tcp_input.c:4370
 tcp_rcv_established+0x7f6/0x3910 net/ipv4/tcp_input.c:6645
 tcp_v4_do_rcv+0xbb8/0x1200 net/ipv4/tcp_ipv4.c:1852
 tcp_v4_rcv+0x2e26/0x4720 net/ipv4/tcp_ipv4.c:2246
 ip_protocol_deliver_rcu+0xba/0x4d0 net/ipv4/ip_input.c:207
 ip_local_deliver_finish+0x3f2/0x6e0 net/ipv4/ip_input.c:241
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 ip_local_deliver+0x19a/0x1f0 net/ipv4/ip_input.c:262
 dst_input include/net/dst.h:480 [inline]
 ip_sublist_rcv_finish net/ipv4/ip_input.c:623 [inline]
 ip_list_rcv_finish+0xa14/0xce0 net/ipv4/ip_input.c:675
 ip_sublist_rcv net/ipv4/ip_input.c:683 [inline]
 ip_list_rcv+0x338/0x450 net/ipv4/ip_input.c:717
 __netif_receive_skb_list_ptype net/core/dev.c:6245 [inline]
 __netif_receive_skb_list_core+0x74c/0x940 net/core/dev.c:6292
 __netif_receive_skb_list net/core/dev.c:6344 [inline]
 netif_receive_skb_list_internal+0x722/0xd40 net/core/dev.c:6435
 gro_normal_list include/net/gro.h:523 [inline]
 gro_normal_list include/net/gro.h:519 [inline]
 gro_flush_normal include/net/gro.h:531 [inline]
 napi_complete_done+0x221/0x940 net/core/dev.c:6803

Memory state around the buggy address:
 ffff8880560d9900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880560d9980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880560d9a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                       ^
 ffff8880560d9a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880560d9b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/06 05:29 upstream 9207d47f966b 26da2c66 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/05/04 01:24 upstream f377d0025eb0 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/04/30 07:36 upstream 57b8e2d666a3 005438fc .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/03/20 18:49 upstream 0e4f8f1a3d08 85bf2a64 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/03/20 02:20 upstream a1d9d8e83378 2f245add .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/03/14 12:07 upstream 1c9982b49613 ee8d34d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/03/14 07:58 upstream 1c9982b49613 ee8d34d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/02/26 08:30 upstream d9d32e5bd5a4 e0f78d93 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/02/14 07:12 upstream 770aaedb461a 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/02/08 03:49 upstream e7aa57247700 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/01/30 20:27 upstream 4d310797262f ea6dba22 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
2026/01/07 21:49 upstream f0b9d8eb98df d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Write in do_con_write
* Struck through repros no longer work on HEAD.