[moderation] [fbdev?] KASAN: slab-out-of-bounds Read in soft_cursor (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f83ec76bf285 Linux 6.17-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17147b12580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f01d8629880e620
dashboard link: https://syzkaller.appspot.com/bug?extid=11ba33d2bf1f33e4f617
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
CC: [del...@gmx.de dri-...@lists.freedesktop.org linux...@vger.kernel.org linux-...@vger.kernel.org sim...@ffwll.ch]

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-f83ec76b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bdedf70f8797/vmlinux-f83ec76b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5bf9318d9242/bzImage-f83ec76b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+11ba33...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in soft_cursor+0x458/0xa10 drivers/video/fbdev/core/softcursor.c:70
Read of size 3 at addr ffff888054a70d7d by task kworker/2:2/3582

CPU: 2 UID: 0 PID: 3582 Comm: kworker/2:2 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events_power_efficient fb_flashcursor
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
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:189
__asan_memcpy+0x23/0x60 mm/kasan/shadow.c:105
soft_cursor+0x458/0xa10 drivers/video/fbdev/core/softcursor.c:70
bit_cursor+0xe8c/0x17e0 drivers/video/fbdev/core/bitblit.c:370
fb_flashcursor drivers/video/fbdev/core/fbcon.c:408 [inline]
fb_flashcursor+0x30d/0x400 drivers/video/fbdev/core/fbcon.c:377
process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3236
process_scheduled_works kernel/workqueue.c:3319 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
kthread+0x3c2/0x780 kernel/kthread.c:463
ret_from_fork+0x56a/0x730 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

Allocated by task 10710:
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]
fbcon_set_font+0x434/0xb80 drivers/video/fbdev/core/fbcon.c:2536
con_font_set drivers/tty/vt/vt.c:4887 [inline]
con_font_op+0x7fb/0xf50 drivers/tty/vt/vt.c:4934
vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline]
vt_ioctl+0x48f/0x30a0 drivers/tty/vt/vt_ioctl.c:751
tty_ioctl+0x661/0x1680 drivers/tty/tty_io.c:2792
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:598 [inline]
__se_sys_ioctl fs/ioctl.c:584 [inline]
__x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:584
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888054a70800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 621 bytes to the right of
allocated 784-byte region [ffff888054a70800, ffff888054a70b10)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x54a70
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 ffff88801b842dc0 ffffea0000d94e00 dead000000000002
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b842dc0 ffffea0000d94e00 dead000000000002
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001529c01 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 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 12, tgid 12 (kworker/u32:0), ts 114834271157, free_ts 113350555070
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]
kzalloc_noprof include/linux/slab.h:1039 [inline]
neigh_alloc net/core/neighbour.c:522 [inline]
___neigh_create+0x14e6/0x28c0 net/core/neighbour.c:656
ip6_finish_output2+0x1299/0x2020 net/ipv6/ip6_output.c:132
__ip6_finish_output+0x3cd/0x1010 net/ipv6/ip6_output.c:215
ip6_finish_output net/ipv6/ip6_output.c:226 [inline]
NF_HOOK_COND include/linux/netfilter.h:307 [inline]
ip6_output+0x1ca/0x3e0 net/ipv6/ip6_output.c:248
dst_output include/net/dst.h:461 [inline]
NF_HOOK include/linux/netfilter.h:318 [inline]
ndisc_send_skb+0xa66/0x1e30 net/ipv6/ndisc.c:512
ndisc_send_rs+0x129/0x670 net/ipv6/ndisc.c:722
addrconf_dad_completed+0x49d/0x10d0 net/ipv6/addrconf.c:4360
addrconf_dad_work+0x855/0x14e0 net/ipv6/addrconf.c:4268
page last free pid 60 tgid 60 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
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_kmalloc+0x8a/0xb0 mm/kasan/common.c:396
kmalloc_noprof include/linux/slab.h:905 [inline]
netdevice_queue_work drivers/infiniband/core/roce_gid_mgmt.c:664 [inline]
netdevice_event+0x365/0x9d0 drivers/infiniband/core/roce_gid_mgmt.c:823
notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2229
call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
call_netdevice_notifiers net/core/dev.c:2281 [inline]
unregister_netdevice_many_notify+0xf76/0x24c0 net/core/dev.c:12166
unregister_netdevice_many net/core/dev.c:12229 [inline]
default_device_exit_batch+0x853/0xaf0 net/core/dev.c:12733
ops_exit_list net/core/net_namespace.c:204 [inline]
ops_undo_list+0x360/0xab0 net/core/net_namespace.c:251
cleanup_net+0x408/0x890 net/core/net_namespace.c:682
process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3236
process_scheduled_works kernel/workqueue.c:3319 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
kthread+0x3c2/0x780 kernel/kthread.c:463
ret_from_fork+0x56a/0x730 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
ffff888054a70c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888054a70c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888054a70d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff888054a70d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888054a70e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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