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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 test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:55 [inline]
BUG: KASAN: null-ptr-deref in trylock_buffer include/linux/buffer_head.h:359 [inline]
BUG: KASAN: null-ptr-deref in lock_buffer include/linux/buffer_head.h:365 [inline]
BUG: KASAN: null-ptr-deref in alloc_branch fs/minix/itree_common.c:88 [inline]
BUG: KASAN: null-ptr-deref in get_block+0x916/0x1600 fs/minix/itree_common.c:191
Write of size 8 at addr 0000000000000000 by task syz-executor.4/31960

CPU: 1 PID: 31960 Comm: syz-executor.4 Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1f0/0x31e lib/dump_stack.c:118
 __kasan_report mm/kasan/report.c:517 [inline]
 kasan_report+0x151/0x1d0 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:183 [inline]
 check_memory_region+0x2b5/0x2f0 mm/kasan/generic.c:192
 instrument_atomic_write include/linux/instrumented.h:71 [inline]
 test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:55 [inline]
 trylock_buffer include/linux/buffer_head.h:359 [inline]
 lock_buffer include/linux/buffer_head.h:365 [inline]
 alloc_branch fs/minix/itree_common.c:88 [inline]
 get_block+0x916/0x1600 fs/minix/itree_common.c:191
 __block_write_begin_int+0x708/0x1a00 fs/buffer.c:2012
 __block_write_begin fs/buffer.c:2062 [inline]
 block_write_begin+0x59/0x280 fs/buffer.c:2121
 minix_write_begin+0x38/0x1f0 fs/minix/inode.c:412
 generic_perform_write+0x23b/0x4e0 mm/filemap.c:3318
 __generic_file_write_iter+0x22b/0x4e0 mm/filemap.c:3447
 generic_file_write_iter+0x4a6/0x650 mm/filemap.c:3479
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0xa08/0xc70 fs/read_write.c:578
 ksys_write+0x11b/0x220 fs/read_write.c:631
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cba9
Code: Bad RIP value.
RSP: 002b:00007fbb99248c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000050f280 RCX: 000000000045cba9
RDX: 0000000008800000 RSI: 0000000020000980 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000d56 R14: 00000000004cfa5a R15: 00007fbb992496d4
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