imgact_aout: Widen the overflow check in exec_aout_imgact()

[markj]

Summary

I suspect this overflow check isn't needed at all, at least today, since
vm_map_insert() will detect wraparound when it creates segments (and
even a check against UINT_MAX is too loose, since the max user address
is AOUT32_USRSTACK == 0xbfc00000). But if we're going to keep this
check, there doesn't seem to be any downside to applying it on all
platforms, before exec_new_vmspace() tears down the current vmspace.

Reported by: Muhammed Sariyildiz <[e-mail]>

[kib]

sys/kern/imgact_aout.c

238–239

Don't we want the same uint64_t cast there as well?

241–245

Add () != 0 since you are changing the line anyway.

[markj]

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