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BUG: KASAN: null-ptr-deref in drop_buffers+0x65/0x4f0
Read of size 4 at addr 0000000000000060 by task syz.1.421/8149

CPU: 1 UID: 0 PID: 8149 Comm: syz.1.421 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 kasan_report+0x118/0x150
 kasan_check_range+0x2b0/0x2c0
 drop_buffers+0x65/0x4f0
 try_to_free_buffers+0x1e1/0x2d0
 shrink_folio_list+0x20ac/0x4cd0
 evict_folios+0x47f2/0x58b0
 try_to_shrink_lruvec+0x8a3/0xb50
 shrink_lruvec+0x49c/0x2980
 shrink_node+0xa4e/0x3760
 do_try_to_free_pages+0x668/0x1960
 try_to_free_mem_cgroup_pages+0x2fa/0x7e0
 try_charge_memcg+0xa40/0x1290
 charge_memcg+0x9f/0x180
 __mem_cgroup_charge+0x25/0x80
 shmem_alloc_and_add_folio+0x7c1/0xf60
 shmem_get_folio_gfp+0x59d/0x1660
 shmem_write_begin+0xf7/0x2b0
 generic_perform_write+0x2c5/0x900
 shmem_file_write_iter+0xf8/0x120
 __kernel_write_iter+0x428/0x910
 dump_user_range+0x8a0/0xc90
 elf_core_dump+0x337b/0x3990
 coredump_write+0x1169/0x1900
 vfs_coredump+0x1daa/0x2a50
 get_signal+0x1109/0x1340
 arch_do_signal_or_restart+0x9a/0x750
 irqentry_exit_to_user_mode+0x81/0x120
 exc_page_fault+0x9f/0xf0
 asm_exc_page_fault+0x26/0x30
RIP: 0033:0x191973878e40
Code: Unable to access opcode bytes at 0x191973878e16.
RSP: 002b:0000200000000078 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007ffb78db5fa0 RCX: 00007ffb78b8ebe9
RDX: 0000200000000080 RSI: 0000200000000070 RDI: 0000000000000000
RBP: 00007ffb78c11e19 R08: 0000200000000100 R09: 0000200000000100
R10: 00002000000000c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffb78db6038 R14: 00007ffb78db5fa0 R15: 00007fff3db57d58
 </TASK>
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