Merge branch 'work.sys_wait' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull wait syscall updates from Al Viro: "Consolidating sys_wait* and compat counterparts. Gets rid of set_fs()/double-copy mess, simplifies the whole thing (lifting the copyouts to the syscalls means less headache in the part that does actual work - fewer failure exits, to start with), gets rid of the overhead of field-by-field __put_user()" * 'work.sys_wait' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: osf_wait4: switch to kernel_wait4() waitid(): switch copyout of siginfo to unsafe_put_user() wait_task_zombie: consolidate info logics kill wait_noreap_copyout() lift getrusage() from wait_noreap_copyout() waitid(2): leave copyout of siginfo to syscall itself kernel_wait4()/kernel_waitid(): delay copying status to userland wait4(2)/waitid(2): separate copying rusage to userland move compat wait4 and waitid next to native variants
2017-07-05 14:10:19 -07:00
parent 3bad2f1c67 92ebce5ac5
commit 4be95131bf
6 changed files with 189 additions and 261 deletions
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -62,6 +62,7 @@
 #include <linux/kcov.h>
 #include <linux/random.h>
 #include <linux/rcuwait.h>
+#include <linux/compat.h>

 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -982,14 +983,21 @@ SYSCALL_DEFINE1(exit_group, int, error_code)
 	return 0;
 }

+struct waitid_info {
+	pid_t pid;
+	uid_t uid;
+	int status;
+	int cause;
+};
+
 struct wait_opts {
 	enum pid_type		wo_type;
 	int			wo_flags;
 	struct pid		*wo_pid;

-	struct siginfo __user	*wo_info;
-	int __user		*wo_stat;
-	struct rusage __user	*wo_rusage;
+	struct waitid_info	*wo_info;
+	int			wo_stat;
+	struct rusage		*wo_rusage;

 	wait_queue_entry_t		child_wait;
 	int			notask_error;
@@ -1036,34 +1044,6 @@ eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
 	return 1;
 }

-static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
-				pid_t pid, uid_t uid, int why, int status)
-{
-	struct siginfo __user *infop;
-	int retval = wo->wo_rusage
-		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
-
-	put_task_struct(p);
-	infop = wo->wo_info;
-	if (infop) {
-		if (!retval)
-			retval = put_user(SIGCHLD, &infop->si_signo);
-		if (!retval)
-			retval = put_user(0, &infop->si_errno);
-		if (!retval)
-			retval = put_user((short)why, &infop->si_code);
-		if (!retval)
-			retval = put_user(pid, &infop->si_pid);
-		if (!retval)
-			retval = put_user(uid, &infop->si_uid);
-		if (!retval)
-			retval = put_user(status, &infop->si_status);
-	}
-	if (!retval)
-		retval = pid;
-	return retval;
-}
-
 /*
 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
@@ -1072,30 +1052,23 @@ static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
 */
 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 {
-	int state, retval, status;
+	int state, status;
 	pid_t pid = task_pid_vnr(p);
 	uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
-	struct siginfo __user *infop;
+	struct waitid_info *infop;

 	if (!likely(wo->wo_flags & WEXITED))
 		return 0;

 	if (unlikely(wo->wo_flags & WNOWAIT)) {
-		int exit_code = p->exit_code;
-		int why;
-
+		status = p->exit_code;
 		get_task_struct(p);
 		read_unlock(&tasklist_lock);
 		sched_annotate_sleep();
-
-		if ((exit_code & 0x7f) == 0) {
-			why = CLD_EXITED;
-			status = exit_code >> 8;
-		} else {
-			why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
-			status = exit_code & 0x7f;
-		}
-		return wait_noreap_copyout(wo, p, pid, uid, why, status);
+		if (wo->wo_rusage)
+			getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
+		put_task_struct(p);
+		goto out_info;
 	}
 	/*
 	 * Move the task's state to DEAD/TRACE, only one thread can do this.
@@ -1168,38 +1141,11 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 		spin_unlock_irq(&current->sighand->siglock);
 	}

-	retval = wo->wo_rusage
-		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
+	if (wo->wo_rusage)
+		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
 	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
 		? p->signal->group_exit_code : p->exit_code;
-	if (!retval && wo->wo_stat)
-		retval = put_user(status, wo->wo_stat);
-
-	infop = wo->wo_info;
-	if (!retval && infop)
-		retval = put_user(SIGCHLD, &infop->si_signo);
-	if (!retval && infop)
-		retval = put_user(0, &infop->si_errno);
-	if (!retval && infop) {
-		int why;
-
-		if ((status & 0x7f) == 0) {
-			why = CLD_EXITED;
-			status >>= 8;
-		} else {
-			why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
-			status &= 0x7f;
-		}
-		retval = put_user((short)why, &infop->si_code);
-		if (!retval)
-			retval = put_user(status, &infop->si_status);
-	}
-	if (!retval && infop)
-		retval = put_user(pid, &infop->si_pid);
-	if (!retval && infop)
-		retval = put_user(uid, &infop->si_uid);
-	if (!retval)
-		retval = pid;
+	wo->wo_stat = status;

 	if (state == EXIT_TRACE) {
 		write_lock_irq(&tasklist_lock);
@@ -1216,7 +1162,21 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 	if (state == EXIT_DEAD)
 		release_task(p);

-	return retval;
+out_info:
+	infop = wo->wo_info;
+	if (infop) {
+		if ((status & 0x7f) == 0) {
+			infop->cause = CLD_EXITED;
+			infop->status = status >> 8;
+		} else {
+			infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
+			infop->status = status & 0x7f;
+		}
+		infop->pid = pid;
+		infop->uid = uid;
+	}
+
+	return pid;
 }

 static int *task_stopped_code(struct task_struct *p, bool ptrace)
@@ -1252,8 +1212,8 @@ static int *task_stopped_code(struct task_struct *p, bool ptrace)
 static int wait_task_stopped(struct wait_opts *wo,
 				int ptrace, struct task_struct *p)
 {
-	struct siginfo __user *infop;
-	int retval, exit_code, *p_code, why;
+	struct waitid_info *infop;
+	int exit_code, *p_code, why;
 	uid_t uid = 0; /* unneeded, required by compiler */
 	pid_t pid;

@@ -1298,34 +1258,21 @@ unlock_sig:
 	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
 	read_unlock(&tasklist_lock);
 	sched_annotate_sleep();
-
-	if (unlikely(wo->wo_flags & WNOWAIT))
-		return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
-
-	retval = wo->wo_rusage
-		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
-	if (!retval && wo->wo_stat)
-		retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
-
-	infop = wo->wo_info;
-	if (!retval && infop)
-		retval = put_user(SIGCHLD, &infop->si_signo);
-	if (!retval && infop)
-		retval = put_user(0, &infop->si_errno);
-	if (!retval && infop)
-		retval = put_user((short)why, &infop->si_code);
-	if (!retval && infop)
-		retval = put_user(exit_code, &infop->si_status);
-	if (!retval && infop)
-		retval = put_user(pid, &infop->si_pid);
-	if (!retval && infop)
-		retval = put_user(uid, &infop->si_uid);
-	if (!retval)
-		retval = pid;
+	if (wo->wo_rusage)
+		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
 	put_task_struct(p);

-	BUG_ON(!retval);
-	return retval;
+	if (likely(!(wo->wo_flags & WNOWAIT)))
+		wo->wo_stat = (exit_code << 8) | 0x7f;
+
+	infop = wo->wo_info;
+	if (infop) {
+		infop->cause = why;
+		infop->status = exit_code;
+		infop->pid = pid;
+		infop->uid = uid;
+	}
+	return pid;
 }

 /*
@@ -1336,7 +1283,7 @@ unlock_sig:
 */
 static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
 {
-	int retval;
+	struct waitid_info *infop;
 	pid_t pid;
 	uid_t uid;

@@ -1361,22 +1308,20 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
 	get_task_struct(p);
 	read_unlock(&tasklist_lock);
 	sched_annotate_sleep();
+	if (wo->wo_rusage)
+		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
+	put_task_struct(p);

-	if (!wo->wo_info) {
-		retval = wo->wo_rusage
-			? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
-		put_task_struct(p);
-		if (!retval && wo->wo_stat)
-			retval = put_user(0xffff, wo->wo_stat);
-		if (!retval)
-			retval = pid;
+	infop = wo->wo_info;
+	if (!infop) {
+		wo->wo_stat = 0xffff;
 	} else {
-		retval = wait_noreap_copyout(wo, p, pid, uid,
-					     CLD_CONTINUED, SIGCONT);
-		BUG_ON(retval == 0);
+		infop->cause = CLD_CONTINUED;
+		infop->pid = pid;
+		infop->uid = uid;
+		infop->status = SIGCONT;
 	}
-
-	return retval;
+	return pid;
 }

 /*
@@ -1604,8 +1549,8 @@ end:
 	return retval;
 }

-SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
-		infop, int, options, struct rusage __user *, ru)
+static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
+			  int options, struct rusage *ru)
 {
 	struct wait_opts wo;
 	struct pid *pid = NULL;
@@ -1643,38 +1588,46 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
 	wo.wo_pid	= pid;
 	wo.wo_flags	= options;
 	wo.wo_info	= infop;
-	wo.wo_stat	= NULL;
 	wo.wo_rusage	= ru;
 	ret = do_wait(&wo);

-	if (ret > 0) {
+	if (ret > 0)
 		ret = 0;
-	} else if (infop) {
-		/*
-		 * For a WNOHANG return, clear out all the fields
-		 * we would set so the user can easily tell the
-		 * difference.
-		 */
-		if (!ret)
-			ret = put_user(0, &infop->si_signo);
-		if (!ret)
-			ret = put_user(0, &infop->si_errno);
-		if (!ret)
-			ret = put_user(0, &infop->si_code);
-		if (!ret)
-			ret = put_user(0, &infop->si_pid);
-		if (!ret)
-			ret = put_user(0, &infop->si_uid);
-		if (!ret)
-			ret = put_user(0, &infop->si_status);
-	}

 	put_pid(pid);
 	return ret;
 }

-SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
-		int, options, struct rusage __user *, ru)
+SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
+		infop, int, options, struct rusage __user *, ru)
+{
+	struct rusage r;
+	struct waitid_info info = {.status = 0};
+	long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
+
+	if (!err) {
+		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
+			return -EFAULT;
+	}
+	if (!infop)
+		return err;
+
+	user_access_begin();
+	unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault);
+	unsafe_put_user(0, &infop->si_errno, Efault);
+	unsafe_put_user((short)info.cause, &infop->si_code, Efault);
+	unsafe_put_user(info.pid, &infop->si_pid, Efault);
+	unsafe_put_user(info.uid, &infop->si_uid, Efault);
+	unsafe_put_user(info.status, &infop->si_status, Efault);
+	user_access_end();
+	return err;
+Efault:
+	user_access_end();
+	return -EFAULT;
+}
+
+long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
+		  struct rusage *ru)
 {
 	struct wait_opts wo;
 	struct pid *pid = NULL;
@@ -1702,14 +1655,29 @@ SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
 	wo.wo_pid	= pid;
 	wo.wo_flags	= options | WEXITED;
 	wo.wo_info	= NULL;
-	wo.wo_stat	= stat_addr;
+	wo.wo_stat	= 0;
 	wo.wo_rusage	= ru;
 	ret = do_wait(&wo);
 	put_pid(pid);
+	if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr))
+		ret = -EFAULT;

 	return ret;
 }

+SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
+		int, options, struct rusage __user *, ru)
+{
+	struct rusage r;
+	long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL);
+
+	if (err > 0) {
+		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
+			return -EFAULT;
+	}
+	return err;
+}
+
 #ifdef __ARCH_WANT_SYS_WAITPID

 /*
@@ -1722,3 +1690,56 @@ SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
 }

 #endif
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE4(wait4,
+	compat_pid_t, pid,
+	compat_uint_t __user *, stat_addr,
+	int, options,
+	struct compat_rusage __user *, ru)
+{
+	struct rusage r;
+	long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL);
+	if (err > 0) {
+		if (ru && put_compat_rusage(&r, ru))
+			return -EFAULT;
+	}
+	return err;
+}
+
+COMPAT_SYSCALL_DEFINE5(waitid,
+		int, which, compat_pid_t, pid,
+		struct compat_siginfo __user *, infop, int, options,
+		struct compat_rusage __user *, uru)
+{
+	struct rusage ru;
+	struct waitid_info info = {.status = 0};
+	long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
+
+	if (!err && uru) {
+		/* kernel_waitid() overwrites everything in ru */
+		if (COMPAT_USE_64BIT_TIME)
+			err = copy_to_user(uru, &ru, sizeof(ru));
+		else
+			err = put_compat_rusage(&ru, uru);
+		if (err)
+			return -EFAULT;
+	}
+
+	if (!infop)
+		return err;
+
+	user_access_begin();
+	unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault);
+	unsafe_put_user(0, &infop->si_errno, Efault);
+	unsafe_put_user((short)info.cause, &infop->si_code, Efault);
+	unsafe_put_user(info.pid, &infop->si_pid, Efault);
+	unsafe_put_user(info.uid, &infop->si_uid, Efault);
+	unsafe_put_user(info.status, &infop->si_status, Efault);
+	user_access_end();
+	return err;
+Efault:
+	user_access_end();
+	return -EFAULT;
+}
+#endif