syzbot

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BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: null-ptr-deref in atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
BUG: KASAN: null-ptr-deref in refcount_sub_and_test include/linux/refcount.h:266 [inline]
BUG: KASAN: null-ptr-deref in refcount_dec_and_test include/linux/refcount.h:294 [inline]
BUG: KASAN: null-ptr-deref in in6_dev_put include/net/addrconf.h:378 [inline]
BUG: KASAN: null-ptr-deref in mld_send_cr net/ipv6/mcast.c:1941 [inline]
BUG: KASAN: null-ptr-deref in mld_ifc_timer_expire+0x84d/0xf10 net/ipv6/mcast.c:2474
Write of size 4 at addr 00000000000001c8 by task syz-executor.4/6483

CPU: 0 PID: 6483 Comm: syz-executor.4 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 __kasan_report mm/kasan/report.c:517 [inline]
 kasan_report.cold+0x5/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 instrument_atomic_write include/linux/instrumented.h:71 [inline]
 atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
 refcount_sub_and_test include/linux/refcount.h:266 [inline]
 refcount_dec_and_test include/linux/refcount.h:294 [inline]
 in6_dev_put include/net/addrconf.h:378 [inline]
 mld_send_cr net/ipv6/mcast.c:1941 [inline]
 mld_ifc_timer_expire+0x84d/0xf10 net/ipv6/mcast.c:2474
 call_timer_fn+0x1ac/0x760 kernel/time/timer.c:1413
 expire_timers kernel/time/timer.c:1458 [inline]
 __run_timers.part.0+0x67c/0xaa0 kernel/time/timer.c:1755
 __run_timers kernel/time/timer.c:1736 [inline]
 run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1768
 __do_softirq+0x1f8/0xb23 kernel/softirq.c:298
 asm_call_irq_on_stack+0xf/0x20
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
 do_softirq_own_stack+0x9b/0xd0 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:393 [inline]
 __irq_exit_rcu kernel/softirq.c:423 [inline]
 irq_exit_rcu+0x235/0x280 kernel/softirq.c:435
 sysvec_apic_timer_interrupt+0x51/0xf0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:196
Code: 48 89 ef 5d e9 71 5e 40 00 5d be 03 00 00 00 e9 a6 b7 49 02 66 0f 1f 44 00 00 48 8b be b0 01 00 00 e8 b4 ff ff ff 31 c0 c3 90 <65> 48 8b 14 25 c0 fe 01 00 65 8b 05 e0 bf 8b 7e a9 00 01 ff 00 48
RSP: 0018:ffffc90015e0f1c8 EFLAGS: 00000246
RAX: 0000000000000002 RBX: ffff8882189753e6 RCX: ffffffff83ebf82f
RDX: 0000000000000000 RSI: ffff888036c68380 RDI: 0000000000000005
RBP: 0000000000000055 R08: 000000000000001d R09: 0000000000000023
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff88800010dc30 R14: dffffc0000000000 R15: ffff88800010dc2c
 fast_imageblit drivers/video/fbdev/core/cfbimgblt.c:258 [inline]
 cfb_imageblit+0x629/0x1010 drivers/video/fbdev/core/cfbimgblt.c:300
 vga_imageblit_expand drivers/video/fbdev/vga16fb.c:1207 [inline]
 vga16fb_imageblit+0x693/0x2210 drivers/video/fbdev/vga16fb.c:1260
 bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:139 [inline]
 bit_putcs+0x6e1/0xd20 drivers/video/fbdev/core/bitblit.c:188
 fbcon_putcs+0x35a/0x450 drivers/video/fbdev/core/fbcon.c:1308
 con_flush drivers/tty/vt/vt.c:2575 [inline]
 vc_con_write_normal drivers/tty/vt/vt.c:2803 [inline]
 do_con_write+0xfab/0x1dd0 drivers/tty/vt/vt.c:2910
 con_write+0x22/0xb0 drivers/tty/vt/vt.c:3250
 n_tty_write+0xa38/0xf80 drivers/tty/n_tty.c:2356
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x4d9/0x870 drivers/tty/tty_io.c:1046
 __kernel_write+0x199/0x570 fs/read_write.c:528
 write_pipe_buf+0x153/0x1f0 fs/splice.c:799
 splice_from_pipe_feed fs/splice.c:502 [inline]
 __splice_from_pipe+0x3dc/0x830 fs/splice.c:626
 splice_from_pipe fs/splice.c:661 [inline]
 default_file_splice_write fs/splice.c:811 [inline]
 do_splice_from fs/splice.c:847 [inline]
 direct_splice_actor+0x228/0x2f0 fs/splice.c:1016
 splice_direct_to_actor+0x38c/0x980 fs/splice.c:971
 do_splice_direct+0x1b3/0x280 fs/splice.c:1059
 do_sendfile+0x55f/0xd40 fs/read_write.c:1548
 __do_compat_sys_sendfile fs/read_write.c:1630 [inline]
 __se_compat_sys_sendfile fs/read_write.c:1613 [inline]
 __ia32_compat_sys_sendfile+0x1e0/0x220 fs/read_write.c:1613
 do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
 __do_fast_syscall_32+0x60/0x90 arch/x86/entry/common.c:137
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7fe7549
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f55e10cc EFLAGS: 00000296 ORIG_RAX: 00000000000000bb
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000000005
RDX: 0000000000000000 RSI: 0000000080004103 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
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