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.

Dmitry V. Levin committed 7 years ago

Commit 028b6e81 parent 964a4ea3 files · +20 −2Browse files

Unified · Split

3 files

arch/x86/ia32/sys_ia32.c +4 −0
include/linux/sched/task.h +1 −0
kernel/fork.c +15 −2

arch/x86/ia32/sys_ia32.c+4−0

 {
 	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),
 		.tls		= tls_val,
 	};
+	if (!legacy_clone_args_valid(&args))
+		return -EINVAL;
 	return _do_fork(&args);
 }

include/linux/sched/task.h+1−0

@@ -89,6 +89,7 @@ extern void exit_files(struct task_struct *); · 88 unmodified lines
89	extern void exit_itimers(struct signal_struct *);	89	extern void exit_itimers(struct signal_struct *);
90		90
91	extern long _do_fork(struct kernel_clone_args *kargs);	91	extern long _do_fork(struct kernel_clone_args *kargs);
		92	extern bool legacy_clone_args_valid(const struct kernel_clone_args *kargs);
92	extern long do_fork(unsigned long, unsigned long, unsigned long, int __user , int __user );	93	extern long do_fork(unsigned long, unsigned long, unsigned long, int __user , int __user );
93	struct task_struct *fork_idle(int);	94	struct task_struct *fork_idle(int);
94	struct mm_struct *copy_init_mm(void);	95	struct mm_struct *copy_init_mm(void);

kernel/fork.c+15−2

 	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. */
 {
 	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),
 		.stack_size	= stack_size,
 	};
+	if (!legacy_clone_args_valid(&args))
+		return -EINVAL;
 	return _do_fork(&args);
 }
 #endif
 		.tls		= tls,
 	};
-	/* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
+	if (!legacy_clone_args_valid(&args))
-	if ((clone_flags & CLONE_PIDFD) && (clone_flags & CLONE_PARENT_SETTID))
 		return -EINVAL;
 	return _do_fork(&args);

clone: fix CLONE_PIDFD support

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