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KASAN: slab-out-of-bounds Write in do_con_write (2)

Status: upstream: reported on 2025/09/06 07:00
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+1046ca04f5ba70aa8206@syzkaller.appspotmail.com
First crash: 22d, last: 13h11m
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [serial?] KASAN: slab-out-of-bounds Write in do_con_write (2) 0 (1) 2025/09/06 07:00
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Write in do_con_write serial 23 4 137d 215d 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:3086 [inline]
BUG: KASAN: slab-out-of-bounds in do_con_write+0x3839/0x8280 drivers/tty/vt/vt.c:3178
Write of size 2 at addr ffff88802ace3f96 by task syz.0.2736/20837

CPU: 0 UID: 0 PID: 20837 Comm: syz.0.2736 Tainted: G     U              syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 vc_con_write_normal drivers/tty/vt/vt.c:3086 [inline]
 do_con_write+0x3839/0x8280 drivers/tty/vt/vt.c:3178
 con_write+0x23/0xb0 drivers/tty/vt/vt.c:3516
 process_output_block drivers/tty/n_tty.c:561 [inline]
 n_tty_write+0x41c/0x11e0 drivers/tty/n_tty.c:2377
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write.constprop.0+0x504/0x9b0 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+0xd4/0x150 drivers/tty/tty_io.c:1105
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x7d0/0x11d0 fs/read_write.c:686
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f964a98eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9648bf6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f964abd6090 RCX: 00007f964a98eba9
RDX: 000000000000005b RSI: 00002000000005c0 RDI: 000000000000000a
RBP: 00007f964aa11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f964abd6128 R14: 00007f964abd6090 R15: 00007ffc633f4028
 </TASK>

Allocated by task 20746:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4376 [inline]
 __kmalloc_noprof+0x223/0x510 mm/slub.c:4388
 kmalloc_noprof include/linux/slab.h:909 [inline]
 tomoyo_realpath_from_path+0xc2/0x6e0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x2ab/0x3c0 security/tomoyo/file.c:771
 tomoyo_file_open+0x6b/0x90 security/tomoyo/tomoyo.c:334
 security_file_open+0x84/0x1e0 security/security.c:3144
 do_dentry_open+0x596/0x1530 fs/open.c:942
 vfs_open+0x82/0x3f0 fs/open.c:1095
 do_open fs/namei.c:3887 [inline]
 path_openat+0x1de4/0x2cb0 fs/namei.c:4046
 do_filp_open+0x20b/0x470 fs/namei.c:4073
 do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1461
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 20746:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x60/0x70 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2422 [inline]
 slab_free mm/slub.c:4695 [inline]
 kfree+0x2b4/0x4d0 mm/slub.c:4894
 tomoyo_realpath_from_path+0x19f/0x6e0 security/tomoyo/realpath.c:286
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x2ab/0x3c0 security/tomoyo/file.c:771
 tomoyo_file_open+0x6b/0x90 security/tomoyo/tomoyo.c:334
 security_file_open+0x84/0x1e0 security/security.c:3144
 do_dentry_open+0x596/0x1530 fs/open.c:942
 vfs_open+0x82/0x3f0 fs/open.c:1095
 do_open fs/namei.c:3887 [inline]
 path_openat+0x1de4/0x2cb0 fs/namei.c:4046
 do_filp_open+0x20b/0x470 fs/namei.c:4073
 do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1461
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802ace2000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 3990 bytes to the right of
 allocated 4096-byte region [ffff88802ace2000, ffff88802ace3000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2ace0
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 ffff88801b842140 ffffea0001dc7a00 dead000000000002
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b842140 ffffea0001dc7a00 dead000000000002
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000ab3801 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 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 19760, tgid 19744 (syz.2.2547), ts 969303718236, free_ts 969259291139
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x132b/0x38e0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:5148
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2492 [inline]
 allocate_slab mm/slub.c:2660 [inline]
 new_slab+0x247/0x330 mm/slub.c:2714
 ___slab_alloc+0xcf2/0x1750 mm/slub.c:3901
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3992
 __slab_alloc_node mm/slub.c:4067 [inline]
 slab_alloc_node mm/slub.c:4228 [inline]
 __do_kmalloc_node mm/slub.c:4375 [inline]
 __kmalloc_noprof+0x2f2/0x510 mm/slub.c:4388
 kmalloc_noprof include/linux/slab.h:909 [inline]
 tomoyo_realpath_from_path+0xc2/0x6e0 security/tomoyo/realpath.c:251
 tomoyo_get_exe+0x63/0xa0 security/tomoyo/util.c:978
 tomoyo_manager security/tomoyo/common.c:943 [inline]
 tomoyo_write_control+0x689/0x1430 security/tomoyo/common.c:2823
 vfs_write+0x29d/0x11d0 fs/read_write.c:684
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 19763 tgid 19762 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0x7d5/0x10f0 mm/page_alloc.c:2895
 __folio_put+0x329/0x450 mm/swap.c:112
 folio_put include/linux/mm.h:1360 [inline]
 put_page include/linux/mm.h:1429 [inline]
 put_netmem net/core/skbuff.c:7370 [inline]
 skb_page_unref include/linux/skbuff_ref.h:43 [inline]
 __skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
 skb_release_data+0x81a/0x9e0 net/core/skbuff.c:1080
 skb_release_all net/core/skbuff.c:1151 [inline]
 __kfree_skb net/core/skbuff.c:1165 [inline]
 kfree_skb_napi_cache net/core/skbuff.c:7162 [inline]
 skb_attempt_defer_free+0x44e/0x620 net/core/skbuff.c:7189
 tcp_eat_recv_skb net/ipv4/tcp.c:1562 [inline]
 tcp_recvmsg_locked+0x1248/0x2870 net/ipv4/tcp.c:2859
 tcp_recvmsg+0x12f/0x680 net/ipv4/tcp.c:2905
 inet_recvmsg+0x12a/0x6a0 net/ipv4/af_inet.c:883
 sock_recvmsg_nosec net/socket.c:1065 [inline]
 sock_recvmsg+0x1b2/0x250 net/socket.c:1087
 __sys_recvfrom+0x203/0x310 net/socket.c:2278
 __do_sys_recvfrom net/socket.c:2293 [inline]
 __se_sys_recvfrom net/socket.c:2289 [inline]
 __x64_sys_recvfrom+0xe0/0x1c0 net/socket.c:2289
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88802ace3e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802ace3f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802ace3f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                         ^
 ffff88802ace4000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88802ace4080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/10 08:09 upstream 9dd1835ecda5 fdeaa69b .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
2025/09/06 06:59 upstream c8ed9b5c02a5 d291dd2d .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
2025/09/02 15:31 upstream b320789d6883 96a211bc .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
2025/08/28 11:24 upstream 07d9df80082b bee60a83 .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
2025/08/27 04:43 upstream fab1beda7597 e12e5ba4 .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
2025/08/19 16:54 upstream be48bcf004f9 523f460e .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.