KASAN: slab-out-of-bounds Read in vcs

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KMSAN: kernel-infoleak in vcs_read (2) serial	C			1556	750d	1905d	22/28	fixed on 2023/02/24 13:50
==================================================================
BUG: KASAN: slab-out-of-bounds in vcs_scr_readw+0xbd/0xd0 drivers/tty/vt/vt.c:4914
Read of size 2 at addr ffff8880308edf60 by task syz.6.2850/19399

CPU: 1 UID: 0 PID: 19399 Comm: syz.6.2850 Not tainted 6.14.0-rc1-syzkaller-00020-g0de63bb7d919 #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
 vcs_scr_readw+0xbd/0xd0 drivers/tty/vt/vt.c:4914
 vcs_read_buf drivers/tty/vt/vc_screen.c:352 [inline]
 vcs_read+0x638/0xbd0 drivers/tty/vt/vc_screen.c:444
 vfs_read+0x1df/0xbf0 fs/read_write.c:563
 ksys_read+0x12b/0x250 fs/read_write.c:708
 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: 0033:0x7effff18cda9
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:00007f000003b038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007effff3a5fa0 RCX: 00007effff18cda9
RDX: 000000000000001f RSI: 0000000020000040 RDI: 0000000000000003
RBP: 00007effff20e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007effff3a5fa0 R15: 00007ffeee5ce648
 </TASK>

Allocated by task 13799:
 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 ffff8880308ec000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 4032 bytes to the right of
 allocated 4000-byte region [ffff8880308ec000, ffff8880308ecfa0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x308e8
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 ffff88801b042140 ffffea0001803800 0000000000000002
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b042140 ffffea0001803800 0000000000000002
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000c23a01 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 6590, tgid 6590 (kworker/u8:13), ts 474896625470, free_ts 474856005900
 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 6590 tgid 6590 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
 __folio_put+0x32a/0x450 mm/swap.c:112
 folio_put include/linux/mm.h:1489 [inline]
 put_page+0x21e/0x280 include/linux/mm.h:1561
 skb_page_unref include/linux/skbuff_ref.h:43 [inline]
 __skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
 skb_release_data+0x4d7/0x730 net/core/skbuff.c:1119
 skb_release_all net/core/skbuff.c:1190 [inline]
 __kfree_skb net/core/skbuff.c:1204 [inline]
 napi_consume_skb+0x1b7/0x220 net/core/skbuff.c:1514
 __free_old_xmit+0x18b/0x640 drivers/net/virtio_net.c:599
 virtnet_free_old_xmit drivers/net/virtio_net.c:632 [inline]
 free_old_xmit+0xbf/0x1b0 drivers/net/virtio_net.c:1067
 virtnet_poll_tx+0xee2/0x14f0 drivers/net/virtio_net.c:3157
 __napi_poll.constprop.0+0xb7/0x550 net/core/dev.c:7106
 napi_poll net/core/dev.c:7175 [inline]
 net_rx_action+0xa94/0x1010 net/core/dev.c:7297
 handle_softirqs+0x213/0x8f0 kernel/softirq.c:561
 __do_softirq kernel/softirq.c:595 [inline]
 invoke_softirq kernel/softirq.c:435 [inline]
 __irq_exit_rcu+0x109/0x170 kernel/softirq.c:662
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:678
 common_interrupt+0xbf/0xe0 arch/x86/kernel/irq.c:278
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693

Memory state around the buggy address:
 ffff8880308ede00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880308ede80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880308edf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                       ^
 ffff8880308edf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880308ee000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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