The initnewcontext function in arch/x86/include/asm/mmucontext.h in the Linux kernel before 4.12.10 does not correctly handle errors from LDT table allocation when forking a new process, allowing a local attacker to achieve a use-after-free or possibly have unspecified other impact by running a specially crafted program. This vulnerability only affected kernels built with CONFIGMODIFYLDTSYSCALL=y.