[moderation] [fbdev?] KASAN: slab-out-of-bounds Read in fb_pad_unaligned_buffer (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3571e8b091f4 Merge tag 'v6.14-rc6-smb3-server-fixes' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1475084c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=317038cbd53153e8
dashboard link: https://syzkaller.appspot.com/bug?extid=be630f22a848c89fe933
compiler: gcc (Debian 12.2.0-14) 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/7feb34a89c2a/non_bootable_disk-3571e8b0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9d41dbc87b0c/vmlinux-3571e8b0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3789a4803b21/bzImage-3571e8b0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+be630f...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in fb_pad_unaligned_buffer+0x43c/0x470 drivers/video/fbdev/core/fbmem.c:116
Read of size 1 at addr ffff88804fef799c by task syz.0.1630/11176

CPU: 0 UID: 0 PID: 11176 Comm: syz.0.1630 Not tainted 6.14.0-rc6-syzkaller-00205-g3571e8b091f4 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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:408 [inline]
print_report+0xc3/0x670 mm/kasan/report.c:521
kasan_report+0xd9/0x110 mm/kasan/report.c:634
fb_pad_unaligned_buffer+0x43c/0x470 drivers/video/fbdev/core/fbmem.c:116
bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:130 [inline]
bit_putcs+0x86a/0xdf0 drivers/video/fbdev/core/bitblit.c:188
fbcon_putcs+0x364/0x480 drivers/video/fbdev/core/fbcon.c:1308
do_update_region+0x1f8/0x3f0 drivers/tty/vt/vt.c:609
update_region+0xc1/0x160 drivers/tty/vt/vt.c:633
vcs_write+0x7cd/0xdb0 drivers/tty/vt/vc_screen.c:698
vfs_write+0x24c/0x1150 fs/read_write.c:677
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: 0033:0x7fa617f8d169
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:00007fa618ead038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fa6181a5fa0 RCX: 00007fa617f8d169
RDX: 0000000000000030 RSI: 00004000000000c0 RDI: 0000000000000004
RBP: 00007fa61800e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa6181a5fa0 R15: 00007ffc2dca84f8
</TASK>

Allocated by task 8626:
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+0x21c/0x510 mm/slub.c:4306
kmalloc_noprof include/linux/slab.h:905 [inline]
fbcon_set_font+0x434/0xb60 drivers/video/fbdev/core/fbcon.c:2516
con_font_set drivers/tty/vt/vt.c:4802 [inline]
con_font_op+0x7fd/0xf50 drivers/tty/vt/vt.c:4849
vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline]
vt_ioctl+0x4ca/0x2f80 drivers/tty/vt/vt_ioctl.c:751
tty_ioctl+0x651/0x15d0 drivers/tty/tty_io.c:2802
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl fs/ioctl.c:892 [inline]
__x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
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 ffff88804fef4000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 7308 bytes to the right of
allocated 7440-byte region [ffff88804fef4000, ffff88804fef5d10)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4fef0
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 ffff88801b043180 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b043180 dead000000000100 dead000000000122
head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea00013fbc01 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 7143, tgid 7140 (syz.2.418), ts 81268002751, free_ts 81237093295
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:4740
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+0xc5d/0x1720 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]
__kmalloc_cache_noprof+0xfa/0x410 mm/slub.c:4320
kmalloc_noprof include/linux/slab.h:901 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]
cryptomgr_schedule_probe crypto/algboss.c:87 [inline]
cryptomgr_notify+0xa8/0xbc0 crypto/algboss.c:225
notifier_call_chain+0xb7/0x410 kernel/notifier.c:85
blocking_notifier_call_chain kernel/notifier.c:380 [inline]
blocking_notifier_call_chain+0x69/0xa0 kernel/notifier.c:368
crypto_probing_notify crypto/api.c:322 [inline]
crypto_alg_mod_lookup+0x2cf/0x4e0 crypto/api.c:352
crypto_type_has_alg+0x2c/0x80 crypto/algapi.c:1006
xfrm_probe_algs net/xfrm/xfrm_algo.c:819 [inline]
xfrm_probe_algs+0x7c/0x3f0 net/xfrm/xfrm_algo.c:812
pfkey_register+0xf6/0x910 net/key/af_key.c:1701
pfkey_process+0x6db/0x840 net/key/af_key.c:2848
page last free pid 7144 tgid 7144 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]
kmem_cache_alloc_noprof+0x226/0x3d0 mm/slub.c:4171
getname_flags.part.0+0x4c/0x550 fs/namei.c:139
getname_flags include/linux/audit.h:322 [inline]
getname+0x8d/0xe0 fs/namei.c:223
do_sys_openat2+0x104/0x1e0 fs/open.c:1422
do_sys_open fs/open.c:1443 [inline]
__do_sys_openat fs/open.c:1459 [inline]
__se_sys_openat fs/open.c:1454 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1454
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

Memory state around the buggy address:
ffff88804fef7880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804fef7900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88804fef7980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88804fef7a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804fef7a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.