On Tue, Oct 01, 2024 at 11:59:01PM +0100, Mark Brown wrote: > When a new thread is created by a thread with GCS enabled the GCS needs > to be specified along with the regular stack. > > Unfortunately plain clone() is not extensible and existing clone3() > users will not specify a stack so all existing code would be broken if > we mandated specifying the stack explicitly. For compatibility with > these cases and also x86 (which did not initially implement clone3() > support for shadow stacks) if no GCS is specified we will allocate one > so when a thread is created which has GCS enabled allocate one for it. > We follow the extensively discussed x86 implementation and allocate > min(RLIMIT_STACK/2, 2G). Since the GCS only stores the call stack and not > any variables this should be more than sufficient for most applications. > > GCSs allocated via this mechanism will be freed when the thread exits. I think Szabolcs mentioned a GCS leak with v12: https://lore.kernel.org/r/ZtrihWQFyb2/XrQV@xxxxxxx (and in some private messages IIRC) Has this been identified? The changelog only mentions a leak in v8. -- Catalin
