audit: type=1804 audit(1589977460.457:143): pid=25020 uid=0 auid=0 ses=4 subj=system_u:system_r:kernel_t:s0 op="invalid_pcr" cause="ToMToU" comm="syz-executor.3" name="/root/syzkaller-testdir066205923/syzkaller.ci5S8x/514/file0" dev="sda1" ino=17280 res=1
audit: type=1804 audit(1589977460.557:144): pid=25020 uid=0 auid=0 ses=4 subj=system_u:system_r:kernel_t:s0 op="invalid_pcr" cause="ToMToU" comm="syz-executor.3" name="/root/syzkaller-testdir066205923/syzkaller.ci5S8x/514/file0" dev="sda1" ino=17280 res=1
==================================================================
BUG: KASAN: use-after-free in __fb_pad_aligned_buffer include/linux/fb.h:663 [inline]
BUG: KASAN: use-after-free in bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
BUG: KASAN: use-after-free in bit_putcs+0xa7a/0xbe0 drivers/video/fbdev/core/bitblit.c:185
Read of size 1 at addr ffff8880a456cbfe by task syz-executor.3/25049

CPU: 0 PID: 25049 Comm: syz-executor.3 Not tainted 4.14.181-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x13e/0x194 lib/dump_stack.c:58
 print_address_description.cold+0x7c/0x1e2 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2ae mm/kasan/report.c:393
 __fb_pad_aligned_buffer include/linux/fb.h:663 [inline]
 bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
 bit_putcs+0xa7a/0xbe0 drivers/video/fbdev/core/bitblit.c:185
 fbcon_putcs+0x3be/0x480 drivers/video/fbdev/core/fbcon.c:1301
 con_flush drivers/tty/vt/vt.c:2199 [inline]
 do_con_write.part.0+0xc27/0x1a20 drivers/tty/vt/vt.c:2446
 do_con_write drivers/tty/vt/vt.c:2218 [inline]
 con_write+0x33/0xc0 drivers/tty/vt/vt.c:2798
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x375/0xe30 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:959 [inline]
 tty_write+0x3f0/0x700 drivers/tty/tty_io.c:1043
 __vfs_write+0xe4/0x630 fs/read_write.c:480
 vfs_write+0x192/0x4e0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0xf2/0x210 fs/read_write.c:582
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45ca29
RSP: 002b:00007fea98037c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000050c640 RCX: 000000000045ca29
RDX: 0000000000001006 RSI: 0000000020001440 RDI: 0000000000000005
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000ce0 R14: 00000000004cf2c6 R15: 00007fea980386d4

Allocated by task 24503:
 save_stack+0x32/0xa0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:529
 __do_kmalloc_node mm/slab.c:3682 [inline]
 __kmalloc_node_track_caller+0x4c/0x70 mm/slab.c:3696
 __kmalloc_reserve.isra.0+0x35/0xd0 net/core/skbuff.c:137
 __alloc_skb+0xca/0x4c0 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:980 [inline]
 mrp_pdu_init net/802/mrp.c:303 [inline]
 mrp_pdu_append_vecattr_event+0x6f1/0xfa0 net/802/mrp.c:402
 mrp_attr_event+0x151/0x1e0 net/802/mrp.c:497
 mrp_mad_event+0x47/0x60 net/802/mrp.c:577
 mrp_join_timer+0x2f/0x80 net/802/mrp.c:594
 call_timer_fn+0x14a/0x650 kernel/time/timer.c:1279
 expire_timers kernel/time/timer.c:1318 [inline]
 __run_timers kernel/time/timer.c:1636 [inline]
 __run_timers kernel/time/timer.c:1604 [inline]
 run_timer_softirq+0x52a/0x1390 kernel/time/timer.c:1649
 __do_softirq+0x254/0x9bf kernel/softirq.c:288

Freed by task 24503:
 save_stack+0x32/0xa0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcb/0x260 mm/slab.c:3815
 skb_free_head+0x83/0xa0 net/core/skbuff.c:554
 skb_release_data+0x528/0x7b0 net/core/skbuff.c:574
 skb_release_all+0x46/0x60 net/core/skbuff.c:631
 __kfree_skb net/core/skbuff.c:645 [inline]
 kfree_skb+0xae/0x340 net/core/skbuff.c:663
 kfree_skb_list+0x3f/0x60 net/core/skbuff.c:672
 __dev_xmit_skb net/core/dev.c:3240 [inline]
 __dev_queue_xmit+0x159d/0x25c0 net/core/dev.c:3493
 mrp_queue_xmit net/802/mrp.c:354 [inline]
 mrp_join_timer+0x4e/0x80 net/802/mrp.c:598
 call_timer_fn+0x14a/0x650 kernel/time/timer.c:1279
 expire_timers kernel/time/timer.c:1318 [inline]
 __run_timers kernel/time/timer.c:1636 [inline]
 __run_timers kernel/time/timer.c:1604 [inline]
 run_timer_softirq+0x52a/0x1390 kernel/time/timer.c:1649
 __do_softirq+0x254/0x9bf kernel/softirq.c:288

The buggy address belongs to the object at ffff8880a456cb80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 126 bytes inside of
 2048-byte region [ffff8880a456cb80, ffff8880a456d380)
The buggy address belongs to the page:
page:ffffea0002915b00 count:1 mapcount:0 mapping:ffff8880a456c300 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff8880a456c300 0000000000000000 0000000100000003
raw: ffffea00027fd0a0 ffffea00014f45a0 ffff88812fe54c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a456ca80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a456cb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a456cb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff8880a456cc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a456cc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================