Unverified Commit 028b6e8a authored by Dmitry V. Levin's avatar Dmitry V. Levin Committed by Christian Brauner
Browse files

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: 7f192e3c ("fork: add clone3")
Bisected-and-tested-by: default avatarAnatoly Pugachev <matorola@gmail.com>
Signed-off-by: default avatarDmitry V. Levin <ldv@altlinux.org>
Link: https://lore.kernel.org/r/20190714162047.GB10389@altlinux.org


Signed-off-by: default avatarChristian Brauner <christian@brauner.io>
parent 964a4eac

arch/x86/ia32/sys_ia32.c

+4 −0
Original line number Original line Diff line number Diff line
@@ -239,6 +239,7 @@ COMPAT_SYSCALL_DEFINE5(x86_clone, unsigned long, clone_flags, 
{

{

	struct kernel_clone_args args = {

	struct kernel_clone_args args = {

		.flags		= (clone_flags & ~CSIGNAL),

		.flags		= (clone_flags & ~CSIGNAL),

		.pidfd		= parent_tidptr,

		.child_tid	= child_tidptr,

		.child_tid	= child_tidptr,

		.parent_tid	= parent_tidptr,

		.parent_tid	= parent_tidptr,

		.exit_signal	= (clone_flags & CSIGNAL),

		.exit_signal	= (clone_flags & CSIGNAL),
@@ -246,5 +247,8 @@ COMPAT_SYSCALL_DEFINE5(x86_clone, unsigned long, clone_flags, 
		.tls		= tls_val,

		.tls		= tls_val,

	};

	};





	if (!legacy_clone_args_valid(&args))

		return -EINVAL;



	return _do_fork(&args);

	return _do_fork(&args);

}
 
}

include/linux/sched/task.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -89,6 +89,7 @@ extern void exit_files(struct task_struct *); 
extern void exit_itimers(struct signal_struct *);

extern void exit_itimers(struct signal_struct *);





extern long _do_fork(struct kernel_clone_args *kargs);

extern long _do_fork(struct kernel_clone_args *kargs);

extern bool legacy_clone_args_valid(const struct kernel_clone_args *kargs);

extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, int __user *);

extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, int __user *);

struct task_struct *fork_idle(int);

struct task_struct *fork_idle(int);

struct mm_struct *copy_init_mm(void);

struct mm_struct *copy_init_mm(void);

kernel/fork.c

+15 −2
Original line number Original line Diff line number Diff line
@@ -2406,6 +2406,16 @@ long _do_fork(struct kernel_clone_args *args) 
	return nr;

	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

#ifndef CONFIG_HAVE_COPY_THREAD_TLS

/* For compatibility with architectures that call do_fork directly rather than

/* For compatibility with architectures that call do_fork directly rather than

 * using the syscall entry points below. */

 * using the syscall entry points below. */
@@ -2417,6 +2427,7 @@ long do_fork(unsigned long clone_flags, 
{

{

	struct kernel_clone_args args = {

	struct kernel_clone_args args = {

		.flags		= (clone_flags & ~CSIGNAL),

		.flags		= (clone_flags & ~CSIGNAL),

		.pidfd		= parent_tidptr,

		.child_tid	= child_tidptr,

		.child_tid	= child_tidptr,

		.parent_tid	= parent_tidptr,

		.parent_tid	= parent_tidptr,

		.exit_signal	= (clone_flags & CSIGNAL),

		.exit_signal	= (clone_flags & CSIGNAL),
@@ -2424,6 +2435,9 @@ long do_fork(unsigned long clone_flags, 
		.stack_size	= stack_size,

		.stack_size	= stack_size,

	};

	};





	if (!legacy_clone_args_valid(&args))

		return -EINVAL;



	return _do_fork(&args);

	return _do_fork(&args);

}

}

#endif

#endif
@@ -2505,8 +2519,7 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 
		.tls		= tls,

		.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 -EINVAL;





	return _do_fork(&args);

	return _do_fork(&args);

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