[PATCH v8 5/7] posix: Add pidfd_spawn and pidfd_spawnp (BZ 30349)
Florian Weimer
fweimer@redhat.com
Thu Aug 24 07:13:35 GMT 2023
* Adhemerval Zanella:
> Returning a pidfd allows a process to keep a race-free handle for a
> child process, otherwise, the caller will need to either use pidfd_open
> (which still might be subject to TOCTOU) or keep the old racy interface
> base on pid_t.
>
> The implementation makes sure that kernel must support the complete
> pidfd interface, meaning that waitid (P_PIDFD) should be supported
> (added on Linux 5.4). It ensures that a non-racy workaround is required
> (such as reading procfs fdinfo pid to use along with wait interfaces).
Sorry, I don't understand the second sentence.
> diff --git a/posix/tst-spawn3.c b/posix/tst-spawn3.c
> index e7ce0fb386..64052dc911 100644
> --- a/posix/tst-spawn3.c
> +++ b/posix/tst-spawn3.c
> @@ -16,6 +16,7 @@
> License along with the GNU C Library; if not, see
> <https://www.gnu.org/licenses/>. */
>
> +#include <assert.h>
Please use TEST_VERIFY_EXIT, see below.
> @@ -75,75 +78,82 @@ do_test (void)
> FAIL_EXIT1 ("create_temp_file: %m");
> break;
> }
> - files[nfiles++] = fd;
> + files[nfiles] = fd;
> }
> + assert (nfiles != 0);
TEST_VERIFY_EXIT (nfiles != 0);
> diff --git a/sysdeps/unix/sysv/linux/bits/spawn_ext.h b/sysdeps/unix/sysv/linux/bits/spawn_ext.h
> index a3aa020d5c..3254cfe9be 100644
> --- a/sysdeps/unix/sysv/linux/bits/spawn_ext.h
> +++ b/sysdeps/unix/sysv/linux/bits/spawn_ext.h
> @@ -37,4 +37,35 @@ extern int posix_spawnattr_setcgroup_np (posix_spawnattr_t *__attr,
>
> #endif /* __USE_MISC */
>
> +#ifdef __USE_GNU
Please use __USE_MISC, so this is available with _DEFAULT_SOURCE (like
the cgroups functions).
> diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
> index f0d4c62ae6..d4ff23d955 100644
> --- a/sysdeps/unix/sysv/linux/spawni.c
> +++ b/sysdeps/unix/sysv/linux/spawni.c
> internal_signal_block_all (&args.oldmask);
> @@ -386,13 +399,16 @@ __spawnix (pid_t * pid, const char *file,
> /* Unsupported flags like CLONE_CLEAR_SIGHAND will be cleared up by
> __clone_internal_fallback. */
> .flags = (set_cgroup ? CLONE_INTO_CGROUP : 0)
> + | (use_pidfd ? CLONE_PIDFD : 0)
> | CLONE_CLEAR_SIGHAND
> | CLONE_VM
> | CLONE_VFORK,
> .exit_signal = SIGCHLD,
> .stack = (uintptr_t) stack,
> .stack_size = stack_size,
> - .cgroup = (set_cgroup ? attrp->__cgroup : 0)
> + .cgroup = (set_cgroup ? attrp->__cgroup : 0),
> + .pidfd = use_pidfd ? (uintptr_t) &args.pidfd : 0,
> + .parent_tid = use_pidfd ? (uintptr_t) &args.pidfd : 0,
The .parent_tid line looks wrong?
Thanks,
Florian
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