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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+0x657/0x1380 fs/minix/itree_common.c:191
Write of size 8 at addr 0000000000000000 by task syz-executor110/9537

CPU: 0 PID: 9537 Comm: syz-executor110 Not tainted 5.6.0-rc6-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+0x188/0x20d lib/dump_stack.c:118
 __kasan_report.cold+0x5/0x32 mm/kasan/report.c:510
 kasan_report+0xe/0x20 mm/kasan/common.c:641
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x128/0x190 mm/kasan/generic.c:192
 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+0x657/0x1380 fs/minix/itree_common.c:191
 minix_get_block+0xe5/0x110 fs/minix/inode.c:376
 __block_write_begin_int+0x490/0x1b00 fs/buffer.c:2008
 __block_write_begin fs/buffer.c:2058 [inline]
 block_write_begin+0x58/0x2e0 fs/buffer.c:2117
 minix_write_begin+0x35/0xe0 fs/minix/inode.c:412
 generic_perform_write+0x20a/0x4e0 mm/filemap.c:3287
 __generic_file_write_iter+0x24c/0x610 mm/filemap.c:3416
 generic_file_write_iter+0x3f0/0x62d mm/filemap.c:3448
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x49c/0x700 fs/read_write.c:483
 __vfs_write+0xc9/0x100 fs/read_write.c:496
 vfs_write+0x262/0x5c0 fs/read_write.c:558
 ksys_write+0x127/0x250 fs/read_write.c:611
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44b389
Code: fd ca fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb ca fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4e9f99ace8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006ddc38 RCX: 000000000044b389
RDX: 000000000000fdef RSI: 00000000200004c0 RDI: 0000000000000005
RBP: 00000000006ddc30 R08: 0000000000000012 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006ddc3c
R13: 00007ffcd0e441ef R14: 00007f4e9f99b9c0 R15: 0000000000000001
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