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BUG: KASAN: out-of-bounds in csd_lock_record+0xcb/0xe0 kernel/smp.c:118
Read of size 8 at addr ffffc90003d17970 by task syz-executor.4/11326

CPU: 0 PID: 11326 Comm: syz-executor.4 Not tainted 5.8.0-rc3-next-20200703-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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x436 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 csd_lock_record+0xcb/0xe0 kernel/smp.c:118
 flush_smp_call_function_queue+0x285/0x730 kernel/smp.c:391
 __sysvec_call_function_single+0x98/0x490 arch/x86/kernel/smp.c:248
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_call_function_single+0xe0/0x120 arch/x86/kernel/smp.c:243
 asm_sysvec_call_function_single+0x12/0x20 arch/x86/include/asm/idtentry.h:604
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:765 [inline]
RIP: 0010:qlink_free mm/kasan/quarantine.c:151 [inline]
RIP: 0010:qlist_free_all+0xfc/0x140 mm/kasan/quarantine.c:167
Code: 50 08 48 8d 4a ff 83 e2 01 48 0f 45 c1 4c 8b 70 18 e9 40 ff ff ff e8 c3 27 c6 ff 48 83 3d eb 55 01 08 00 74 36 4c 89 ff 57 9d <0f> 1f 44 00 00 4d 85 e4 75 9e 49 c7 45 08 00 00 00 00 49 c7 45 00
RSP: 0018:ffffc900060c7dc8 EFLAGS: 00000282
RAX: 0000000000ae1853 RBX: ffff88808f4a0000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000282
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88809b2f14c0
R13: ffffc900060c7e00 R14: ffff8880aa000900 R15: 0000000000000282
 quarantine_reduce+0x17e/0x200 mm/kasan/quarantine.c:260
 __kasan_kmalloc.constprop.0+0x9e/0xd0 mm/kasan/common.c:475
 slab_post_alloc_hook mm/slab.h:535 [inline]
 slab_alloc mm/slab.c:3316 [inline]
 __do_kmalloc mm/slab.c:3657 [inline]
 __kmalloc_track_caller+0x172/0x4d0 mm/slab.c:3674
 memdup_user+0x22/0xd0 mm/util.c:172
 strndup_user+0x70/0xe0 mm/util.c:231
 copy_mount_string fs/namespace.c:3139 [inline]
 __do_sys_mount fs/namespace.c:3432 [inline]
 __se_sys_mount fs/namespace.c:3424 [inline]
 __x64_sys_mount+0xe6/0x230 fs/namespace.c:3424
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:367
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45f57a
Code: Bad RIP value.
RSP: 002b:00007f0fb1f90a68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000000000050a560 RCX: 000000000045f57a
RDX: 00007f0fb1f90ae0 RSI: 0000000000000000 RDI: 00007f0fb1f90b00
RBP: 000000000078bf00 R08: 00007f0fb1f90b40 R09: 00007f0fb1f90ae0
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000c3b R14: 00000000004ce8d8 R15: 00007f0fb1f916d4


Memory state around the buggy address:
 ffffc90003d17800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003d17880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90003d17900: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00
                                                                ^
 ffffc90003d17980: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003d17a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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