file: /proc/sys/kernel/sysctl_writes_strict
variable: kernel.sysctl_writes_strict
Official reference

Control how file position affects the behavior of updating sysctl values via the /proc/sys interface:

-1 - Legacy per-write sysctl value handling, with no printk warnings. Each write syscall must fully contain the sysctl value to be written, and multiple writes on the same sysctl file descriptor will rewrite the sysctl value, regardless of file position. 0 - Same behavior as above, but warn about processes that perform writes to a sysctl file descriptor when the file position is not 0. 1 - (default) Respect file position when writing sysctl strings. Multiple writes will append to the sysctl value buffer. Anything past the max length of the sysctl value buffer will be ignored. Writes to numeric sysctl entries must always be at file position 0 and the value must be fully contained in the buffer sent in the write syscall.