clone: fix CLONE_PIDFD support
The introduction of clone3 syscall accidentally broke CLONE_PIDFD
support in traditional clone syscall on compat x86 and those
architectures that use do_fork to implement clone syscall.
This bug was found by strace test suite.
Link: https://strace.io/logs/strace/2019-07-12
Fixes: 7f192e3cd316 ("fork: add clone3")
Bisected-and-tested-by: Anatoly Pugachev <matorola@gmail.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Link: https://lore.kernel.org/r/20190714162047.GB10389@altlinux.org
Signed-off-by: Christian Brauner <christian@brauner.io>
diff --git a/kernel/fork.c b/kernel/fork.c
index 8f3e2d9..ef1e05a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2406,6 +2406,16 @@
return nr;
}
+bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
+{
+ /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
+ if ((kargs->flags & CLONE_PIDFD) &&
+ (kargs->flags & CLONE_PARENT_SETTID))
+ return false;
+
+ return true;
+}
+
#ifndef CONFIG_HAVE_COPY_THREAD_TLS
/* For compatibility with architectures that call do_fork directly rather than
* using the syscall entry points below. */
@@ -2417,6 +2427,7 @@
{
struct kernel_clone_args args = {
.flags = (clone_flags & ~CSIGNAL),
+ .pidfd = parent_tidptr,
.child_tid = child_tidptr,
.parent_tid = parent_tidptr,
.exit_signal = (clone_flags & CSIGNAL),
@@ -2424,6 +2435,9 @@
.stack_size = stack_size,
};
+ if (!legacy_clone_args_valid(&args))
+ return -EINVAL;
+
return _do_fork(&args);
}
#endif
@@ -2505,8 +2519,7 @@
.tls = tls,
};
- /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
- if ((clone_flags & CLONE_PIDFD) && (clone_flags & CLONE_PARENT_SETTID))
+ if (!legacy_clone_args_valid(&args))
return -EINVAL;
return _do_fork(&args);