The MUSL implementation of sigaltstack checks that the ss.ss_size is
larger or equal than the MINSIGSTKSZ even when the ss_flags is set
to SS_DISABLE even though Linux man page for sigaltstack states that
when this flag is set, all other ss fields are ignored.
We were not setting the ss_size in this case and it was causing a memory
leak for each thread that has terminated on MUSL based Linux distros
like Alpine.
Glibc implementation doesn't check the ss_size when the SS_DISABLE is set
so the problem was really MUSL specific.
Commit migrated from https://github.com/dotnet/coreclr/commit/
83bdd210b40dac4d42ca8775bfe63d935ab9af2c
void FreeSignalAlternateStack()
{
stack_t ss, oss;
+ // The man page for sigaltstack says that when the ss.ss_flags is set to SS_DISABLE,
+ // all other ss fields are ignored. However, MUSL implementation checks that the
+ // ss_size is >= MINSIGSTKSZ even in this case.
+ ss.ss_size = MINSIGSTKSZ;
ss.ss_flags = SS_DISABLE;
int st = sigaltstack(&ss, &oss);
if ((st == 0) && (oss.ss_flags != SS_DISABLE))