panic: kernel diagnostic assertion "len >= 0 && !M_READONLY(m)" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/uipc_mbuf.c", line 1384
Stopped at      db_enter+0x18:  addq    $0x8,%rsp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
 487408   3951      0           0          0    0  syz-executor.2
*507062   3951      0           0  0x4000000    1K syz-executor.2
db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:440
panic(ffffffff82576625) at panic+0x177 sys/kern/subr_prf.c:202
__assert(ffffffff825e9a2c,ffffffff8255f03b,568,ffffffff8258d88a) at __assert+0x25 sys/kern/subr_prf.c:161
m_align(fffffd8064508400,ffffffd5) at m_align+0x1a0 sys/kern/uipc_mbuf.c:1385
bpf_movein(ffff8000290cb360,ffff800000c96200,ffff8000290cb0c8,ffff8000290cafc8) at bpf_movein+0x25e sys/net/bpf.c:228
bpfwrite(31700,ffff8000290cb360,1) at bpfwrite+0x169 sys/net/bpf.c:644
spec_write(ffff8000290cb1c0) at spec_write+0xd4 sys/kern/spec_vnops.c:309
VOP_WRITE(fffffd806514b968,ffff8000290cb360,1,fffffd807f7d8840) at VOP_WRITE+0xbf sys/kern/vfs_vops.c:245
vn_write(fffffd8067102b50,ffff8000290cb360,1) at vn_write+0x1a1 sys/kern/vfs_vnops.c:414
dofilewritev(ffff800021142a88,3,ffff8000290cb360,1,ffff8000290cb460) at dofilewritev+0x19c sys/kern/sys_generic.c:381
sys_pad_pwrite(ffff800021142a88,ffff8000290cb408,ffff8000290cb460) at sys_pad_pwrite+0x92 sys_pwrite sys/kern/vfs_syscalls.c:3354 [inline]
sys_pad_pwrite(ffff800021142a88,ffff8000290cb408,ffff8000290cb460) at sys_pad_pwrite+0x92 sys/kern/vfs_syscalls.c:3426
syscall(ffff8000290cb4d0) at syscall+0x489 mi_syscall sys/sys/syscall_mi.h:102 [inline]
syscall(ffff8000290cb4d0) at syscall+0x489 sys/arch/amd64/amd64/trap.c:585
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xc6e429a31b0, count: 2
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