remove explicit locking to prevent __synccall setuid during posix_spawn

[musl] / src / process / posix_spawn.c

diff --git a/src/process/posix_spawn.c b/src/process/posix_spawn.c
index c55907d..e6a031c 100644 (file)
--- a/src/process/posix_spawn.c
+++ b/src/process/posix_spawn.c
@@ -10,12 +10,6 @@
 #include "fdop.h"
 #include "libc.h"
 
-static void dummy_0()
-{
-}
-weak_alias(dummy_0, __acquire_ptc);
-weak_alias(dummy_0, __release_ptc);
-
 struct args {
        int p[2];
        sigset_t oldmask;
@@ -144,23 +138,16 @@ int __posix_spawnx(pid_t *restrict res, const char *restrict path,
        args.envp = envp;
        pthread_sigmask(SIG_BLOCK, SIGALL_SET, &args.oldmask);
 
-       /* This lock prevents setuid/setgid operations while the parent
-        * is sharing memory with the child. Situations where processes
-        * with different permissions share VM are fundamentally unsafe. */
-       __acquire_ptc();
        pid = __clone(child, stack+sizeof stack, CLONE_VM|SIGCHLD, &args);
        close(args.p[1]);
 
        if (pid > 0) {
-               if (read(args.p[0], &ec, sizeof ec) < sizeof ec) ec = 0;
+               if (read(args.p[0], &ec, sizeof ec) != sizeof ec) ec = 0;
                else waitpid(pid, &(int){0}, 0);
        } else {
                ec = -pid;
        }
 
-       /* At this point, the child has either exited or successfully
-        * performed exec, so the lock may be released. */
-       __release_ptc();
        close(args.p[0]);
 
        if (!ec) *res = pid;