[PATCH 4.19] sysctl: handle overflow in proc_get_long

Hi,

this upstream patch 7f2923c4f73f21cfd714d12a2d48de8c21f11cfe, should also be applied to 4.19. The other patch of this series (sysctl: handle overflow for file-max) was already applied.

This was found by ltp test (sysctl02).

Thanks, Joerg