[PATCH] compat emulation for posix message queues

From: Arnd Bergmann <arnd@arndb.de>

I have tested the code with the open posix test suite and found the same
four failures for both 64-bit and compat mode, most tests pass.  The patch
is against -mc1, but I guess it also applies to the other trees around.

What worries me more than mq_attr compatibility is the conversion of struct
sigevent, which might turn out really hard when more fields in there are
used.  AFAICS, the only other part in the kernel ABI is sys_timer_create(),
so maybe it's not too late to deprecate the current structure and create a
structure that can be used properly for compat syscalls.

2 files changed, 198 insertions, 1 deletions

diff --git a/ipc/Makefile b/ipc/Makefile
index 913790207d8537..0a6d626cd79400 100644
--- a/ipc/Makefile
+++ b/ipc/Makefile
@@ -4,5 +4,6 @@
 
 obj-$(CONFIG_SYSVIPC_COMPAT) += compat.o
 obj-$(CONFIG_SYSVIPC) += util.o msgutil.o msg.o sem.o shm.o
-obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o
+obj_mq-$(CONFIG_COMPAT) += compat_mq.o
+obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o $(obj_mq-y)
 
diff --git a/ipc/compat_mq.c b/ipc/compat_mq.c
new file mode 100644
index 00000000000000..1520df89c424a2
--- /dev/null
+++ b/ipc/compat_mq.c
@@ -0,0 +1,196 @@
+/*
+ *  ipc/compat_mq.c
+ *    32 bit emulation for POSIX message queue system calls
+ *
+ *    Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ *    Author: Arnd Bergmann <arnd@arndb.de>
+ */
+
+#include <linux/compat.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/mqueue.h>
+#include <linux/syscalls.h>
+
+#include <asm/uaccess.h>
+
+struct compat_mq_attr {
+	compat_long_t mq_flags;      /* message queue flags		     */
+	compat_long_t mq_maxmsg;     /* maximum number of messages	     */
+	compat_long_t mq_msgsize;    /* maximum message size		     */
+	compat_long_t mq_curmsgs;    /* number of messages currently queued  */
+	compat_long_t __reserved[4]; /* ignored for input, zeroed for output */
+};
+
+static inline int get_compat_mq_attr(struct mq_attr *attr,
+			const struct compat_mq_attr __user *uattr)
+{
+	if (verify_area(VERIFY_READ, uattr, sizeof *uattr))
+		return -EFAULT;
+
+	return __get_user(attr->mq_flags, &uattr->mq_flags)
+		| __get_user(attr->mq_maxmsg, &uattr->mq_maxmsg)
+		| __get_user(attr->mq_msgsize, &uattr->mq_msgsize)
+		| __get_user(attr->mq_curmsgs, &uattr->mq_curmsgs);
+}
+
+static inline int put_compat_mq_attr(const struct mq_attr *attr,
+			struct compat_mq_attr __user *uattr)
+{
+	if (clear_user(uattr, sizeof *uattr))
+		return -EFAULT;
+
+	return __put_user(attr->mq_flags, &uattr->mq_flags)
+		| __put_user(attr->mq_maxmsg, &uattr->mq_maxmsg)
+		| __put_user(attr->mq_msgsize, &uattr->mq_msgsize)
+		| __put_user(attr->mq_curmsgs, &uattr->mq_curmsgs);
+}
+
+asmlinkage long compat_sys_mq_open(const char __user *u_name,
+			int oflag, compat_mode_t mode,
+			struct compat_mq_attr __user *u_attr)
+{
+	struct mq_attr attr;
+	mm_segment_t oldfs;
+	char *name;
+	long ret;
+
+	if ((oflag & O_CREAT) == 0 || !u_attr)
+		return sys_mq_open(u_name, oflag, mode, 0);
+
+	if (get_compat_mq_attr(&attr, u_attr))
+		return -EFAULT;
+
+	name = getname(u_name);
+	if (IS_ERR(name))
+		return PTR_ERR(name);
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+	ret = sys_mq_open(name, oflag, mode, &attr);
+	set_fs(oldfs);
+
+	putname(name);
+	return ret;
+}
+
+static struct timespec __user *compat_prepare_timeout(
+			const struct compat_timespec __user *u_abs_timeout)
+{
+	struct timespec ts, __user *u_ts;
+
+	if (!u_abs_timeout)
+		return 0;
+
+	u_ts = compat_alloc_user_space(sizeof(*u_ts));
+	if (get_compat_timespec(&ts, u_abs_timeout)
+		|| copy_to_user(u_ts, &ts, sizeof(*u_ts)))
+		return ERR_PTR(-EFAULT);
+
+	return u_ts;
+}
+
+asmlinkage long compat_sys_mq_timedsend(mqd_t mqdes,
+			const char __user *u_msg_ptr,
+			size_t msg_len, unsigned int msg_prio,
+			const struct compat_timespec __user *u_abs_timeout)
+{
+	struct timespec __user *u_ts;
+
+	u_ts = compat_prepare_timeout(u_abs_timeout);
+	if (IS_ERR(u_ts))
+		return -EFAULT;
+
+	return sys_mq_timedsend(mqdes, u_msg_ptr, msg_len,
+			msg_prio, u_ts);
+}
+
+asmlinkage ssize_t compat_sys_mq_timedreceive(mqd_t mqdes,
+			char __user *u_msg_ptr,
+			size_t msg_len, unsigned int __user *u_msg_prio,
+			const struct compat_timespec __user *u_abs_timeout)
+{
+	struct timespec *u_ts;
+
+	u_ts = compat_prepare_timeout(u_abs_timeout);
+	if (IS_ERR(u_ts))
+		return -EFAULT;
+
+	return sys_mq_timedreceive(mqdes, u_msg_ptr, msg_len,
+			u_msg_prio, u_ts);
+}
+
+static int get_compat_sigevent(struct sigevent *event,
+		const struct compat_sigevent __user *u_event)
+{
+	if (verify_area(VERIFY_READ, u_event, sizeof(*u_event)))
+		return -EFAULT;
+
+	return __get_user(event->sigev_value.sival_int,
+			  &u_event->sigev_value.sival_int)
+	     | __get_user(event->sigev_signo, &u_event->sigev_signo)
+	     | __get_user(event->sigev_notify, &u_event->sigev_notify)
+	     | __get_user(event->sigev_notify_thread_id,
+			  &u_event->sigev_notify_thread_id);
+}
+
+asmlinkage long compat_sys_mq_notify(mqd_t mqdes,
+			const struct compat_sigevent __user *u_notification)
+{
+	mm_segment_t oldfs;
+	struct sigevent notification;
+	char cookie[NOTIFY_COOKIE_LEN];
+	compat_uptr_t u_cookie;
+	long ret;
+
+	if (!u_notification)
+		return sys_mq_notify(mqdes, 0);
+
+	if (get_compat_sigevent(&notification, u_notification))
+		return -EFAULT;
+
+	if (notification.sigev_notify == SIGEV_THREAD) {
+		u_cookie = (compat_uptr_t)notification.sigev_value.sival_int;
+		if (copy_from_user(cookie, compat_ptr(u_cookie),
+						NOTIFY_COOKIE_LEN)) {
+			return -EFAULT;
+		}
+		notification.sigev_value.sival_ptr = cookie;
+	}
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+	ret = sys_mq_notify(mqdes, &notification);
+	set_fs(oldfs);
+
+	return ret;
+}
+
+asmlinkage long compat_sys_mq_getsetattr(mqd_t mqdes,
+			const struct compat_mq_attr __user *u_mqstat,
+			struct compat_mq_attr __user *u_omqstat)
+{
+	struct mq_attr mqstat, omqstat;
+	struct mq_attr *p_mqstat = 0, *p_omqstat = 0;
+	mm_segment_t oldfs;
+	long ret;
+
+	if (u_mqstat) {
+		p_mqstat = &mqstat;
+		if (get_compat_mq_attr(p_mqstat, u_mqstat))
+			return -EFAULT;
+	}
+
+	if (u_omqstat)
+		p_omqstat = &omqstat;
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+	ret = sys_mq_getsetattr(mqdes, p_mqstat, p_omqstat);
+	set_fs(oldfs);
+
+	if (ret)
+		return ret;
+
+	return (u_omqstat) ? put_compat_mq_attr(&omqstat, u_omqstat) : 0;
+}