[syzbot] [serial?] KASAN: slab-out-of-bounds Write in do_con_write

From: syzbot
Date: Fri Feb 07 2025 - 08:31:35 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 2014c95afece Linux 6.14-rc1
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13dd5724580000
kernel config: https://syzkaller.appspot.com/x/.config?x=90331d51f9d6fa1c
dashboard link: https://syzkaller.appspot.com/bug?extid=8da8533727fc2b735c3e
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e059c9dab7dc/disk-2014c95a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0bce0f9fa4d8/vmlinux-2014c95a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6576d9f586f6/bzImage-2014c95a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8da8533727fc2b735c3e@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-out-of-bounds in vc_con_write_normal drivers/tty/vt/vt.c:3010 [inline]
BUG: KASAN: slab-out-of-bounds in do_con_write+0x33f8/0x7d00 drivers/tty/vt/vt.c:3096
Write of size 2 at addr ffff88807b055fc2 by task syz.3.678/8391

CPU: 1 UID: 0 PID: 8391 Comm: syz.3.678 Not tainted 6.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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+0xc3/0x620 mm/kasan/report.c:489
kasan_report+0xd9/0x110 mm/kasan/report.c:602
vc_con_write_normal drivers/tty/vt/vt.c:3010 [inline]
do_con_write+0x33f8/0x7d00 drivers/tty/vt/vt.c:3096
con_write+0x23/0xb0 drivers/tty/vt/vt.c:3432
process_output_block drivers/tty/n_tty.c:574 [inline]
n_tty_write+0x419/0x1140 drivers/tty/n_tty.c:2389
iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
file_tty_write.constprop.0+0x506/0x9a0 drivers/tty/tty_io.c:1090
tty_write drivers/tty/tty_io.c:1111 [inline]
redirected_tty_write drivers/tty/tty_io.c:1134 [inline]
redirected_tty_write+0xcc/0x140 drivers/tty/tty_io.c:1114
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0x5ae/0x1150 fs/read_write.c:679
ksys_write+0x12b/0x250 fs/read_write.c:731
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f452738cda9
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:00007f45251f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f45275a5fa0 RCX: 00007f452738cda9
RDX: 000000000000002b RSI: 0000000020000840 RDI: 0000000000000002
RBP: 00007f452740e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f45275a5fa0 R15: 00007ffda091f458
</TASK>

Allocated by task 6754:
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:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4294 [inline]
__kmalloc_noprof+0x21a/0x4f0 mm/slub.c:4306
kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]
vc_do_resize+0x1da/0x10f0 drivers/tty/vt/vt.c:1174
vc_resize include/linux/vt_kern.h:49 [inline]
vgacon_init+0x37c/0x440 drivers/video/console/vgacon.c:392
visual_init+0x31d/0x620 drivers/tty/vt/vt.c:1011
do_bind_con_driver.isra.0+0x57a/0xbf0 drivers/tty/vt/vt.c:3831
do_unbind_con_driver+0x571/0x6d0 drivers/tty/vt/vt.c:3940
vt_unbind drivers/tty/vt/vt.c:4026 [inline]
store_bind+0x421/0x760 drivers/tty/vt/vt.c:4061
dev_attr_store+0x55/0x80 drivers/base/core.c:2439
sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139
kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0x5ae/0x1150 fs/read_write.c:679
ksys_write+0x12b/0x250 fs/read_write.c:731
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807b054000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 4130 bytes to the right of
allocated 4000-byte region [ffff88807b054000, ffff88807b054fa0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b050
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b042140 0000000000000000 0000000000000001
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b042140 0000000000000000 0000000000000001
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001ec1401 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 12, tgid 12 (kworker/u8:1), ts 161558148619, free_ts 161445411154
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1551
prep_new_page mm/page_alloc.c:1559 [inline]
get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3477
__alloc_frozen_pages_noprof+0x221/0x2470 mm/page_alloc.c:4739
alloc_pages_mpol+0x1fc/0x540 mm/mempolicy.c:2270
alloc_slab_page mm/slub.c:2423 [inline]
allocate_slab mm/slub.c:2587 [inline]
new_slab+0x23d/0x330 mm/slub.c:2640
___slab_alloc+0xbfa/0x1600 mm/slub.c:3826
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3916
__slab_alloc_node mm/slub.c:3991 [inline]
slab_alloc_node mm/slub.c:4152 [inline]
__do_kmalloc_node mm/slub.c:4293 [inline]
__kmalloc_node_track_caller_noprof+0x2ee/0x520 mm/slub.c:4313
kmalloc_reserve+0xef/0x2c0 net/core/skbuff.c:609
__alloc_skb+0x164/0x380 net/core/skbuff.c:678
alloc_skb include/linux/skbuff.h:1331 [inline]
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:748 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline]
nsim_dev_trap_report_work+0x2af/0xd20 drivers/net/netdevsim/dev.c:851
process_one_work+0x958/0x1b30 kernel/workqueue.c:3236
process_scheduled_works kernel/workqueue.c:3317 [inline]
worker_thread+0x6c8/0xf00 kernel/workqueue.c:3398
kthread+0x3af/0x750 kernel/kthread.c:464
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
page last free pid 6547 tgid 6539 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1127 [inline]
free_frozen_pages+0x6db/0xfb0 mm/page_alloc.c:2660
__put_partials+0x14c/0x170 mm/slub.c:3153
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4e/0x120 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4115 [inline]
slab_alloc_node mm/slub.c:4164 [inline]
__kmalloc_cache_noprof+0x202/0x420 mm/slub.c:4320
kmalloc_noprof include/linux/slab.h:901 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]
rxrpc_service_prealloc+0xda/0x1a0 net/rxrpc/call_accept.c:166
rxrpc_listen+0x227/0x330 net/rxrpc/af_rxrpc.c:236
afs_open_socket+0x24e/0x350 fs/afs/rxrpc.c:90
afs_net_init+0x95d/0xc60 fs/afs/main.c:123
ops_init+0x1df/0x5f0 net/core/net_namespace.c:138
setup_net+0x21f/0x860 net/core/net_namespace.c:362
copy_net_ns+0x2b4/0x6c0 net/core/net_namespace.c:516
create_new_namespaces+0x3ea/0xad0 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0xc0/0x1f0 kernel/nsproxy.c:228
ksys_unshare+0x45d/0xa40 kernel/fork.c:3342

Memory state around the buggy address:
ffff88807b055e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807b055f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807b055f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88807b056000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88807b056080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

---
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Next message: FUJITA Tomonori: "[PATCH v10 0/8] rust: Add IO polling"
Previous message: syzbot: "[syzbot] [v9fs?] KCSAN: data-race in p9_conn_cancel / p9_poll_workfn (9)"
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