path: root/src/process/posix_spawn.c
diff options
authorRich Felker <>2013-04-26 15:09:49 -0400
committerRich Felker <>2013-04-26 15:09:49 -0400
commita0473a0c826016aec1181819fcd4fff5c074f042 (patch)
tree141eb6c44848881263145754b2d323c98739fa05 /src/process/posix_spawn.c
parent43653c1250ad5eb5385d7e08292ad047420f8d25 (diff)
remove explicit locking to prevent __synccall setuid during posix_spawn
for the duration of the vm-sharing clone used by posix_spawn, all signals are blocked in the parent process, including implementation-internal signals. since __synccall cannot do anything until successfully signaling all threads, the fact that signals are blocked automatically yields the necessary safety. aside from debloating and general simplification, part of the motivation for removing the explicit lock is to simplify the synchronization logic of __synccall in hopes that it can be made async-signal-safe, which is needed to make setuid and setgid, which depend on __synccall, conform to the standard. whether this will be possible remains to be seen.
Diffstat (limited to 'src/process/posix_spawn.c')
1 files changed, 0 insertions, 13 deletions
diff --git a/src/process/posix_spawn.c b/src/process/posix_spawn.c
index dd450129..e6a031cc 100644
--- 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;
@@ -144,10 +138,6 @@ 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);
@@ -158,9 +148,6 @@ int __posix_spawnx(pid_t *restrict res, const char *restrict path,
ec = -pid;
- /* At this point, the child has either exited or successfully
- * performed exec, so the lock may be released. */
- __release_ptc();
if (!ec) *res = pid;