arm64: Check user stack pointer on syscall entry

Allow the user stack pointer value to be checked on system call entry
and deliver a SIGSEGV if the check does not pass.

Cc: Jann Horn <jannh@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2 files changed