Created attachment 15689 [details]
Reproducer

Dynamic TLS allocated through pthread_key_create or tss_create are not unique if the calls are made in different link namespaces. This means calls to pthread_setspecific/tss_set in one link namespace may overwrite values previously set in another link namespace, and vice versa. Both POSIX and C11 thread interfaces are affected.

Reproducer attached, just run `make`:

    ❯ make
    ...snip...
    ./main-pthread
    [main] Allocated TLS handle: 0
    [main] Set TLS value to: 0x55b0b87b01c9
    [main] Calling into private link namespace...
    [private] Allocated TLS handle: 0
    [private] Set TLS value to: 0x7f6069eaa159
    [main] TLS value is now: 0x7f6069eaa159... FAIL (overwritten)
    ./main-c11
    ...repeats for C11 threads interface...