Linux is a mostly POSIX-compliant Unix-inspired operating system kernel, originally implemented by Linus Torvalds and now maintained as an international project. It's the base and common namegiver to a wide array of Linux distributions. The kernel provides all modern Unix-y features, like true process multitasking, virtual memory, virtual and clustered filesystem support, complex networking and extensive support for various hardware and machine platforms.
minor feature: Linux 4.12.2, x86/mm/pat: Don't report PAT on CPUs that don't support it, ext4: check return value of kstrtoull correctly in reserved_clusters_store, crypto: rsa-pkcs1pad - use constant time memory comparison for MACs, crypto: caam - gfp allocation flags (part I), staging: comedi: clean-up of comedi_class in comedi_init(), staging: vt6556: vnt_start missing call to vnt_key_init_table. locking/rwsem-spinlock: EINTR branch in __down_write_common(), proc: proc_sys_prune_dcache to hold a sb reference, imx-serial: RX DMA startup latency, mqueue: a use-after-free in sys_mq_notify()