[PATCH 2/2] PM / sleep: handle the compat case in snapshot_set_swap_area

[Christoph Hellwig]

Use in_compat_syscall to copy directly from the 32-bit ABI structure.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 kernel/power/user.c | 54 ++++++++++++++++++---------------------------
 1 file changed, 22 insertions(+), 32 deletions(-)

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 0cb555f526e4..7959449765d9 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -196,28 +196,44 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf,
 	return res;
 }
 
+struct compat_resume_swap_area {
+	compat_loff_t offset;
+	u32 dev;
+} __packed;
+
 static int snapshot_set_swap_area(struct snapshot_data *data,
 		void __user *argp)
 {
-	struct resume_swap_area swap_area;
 	sector_t offset;
 	dev_t swdev;
 
 	if (swsusp_swap_in_use())
 		return -EPERM;
-	if (copy_from_user(&swap_area, argp, sizeof(swap_area)))
-		return -EFAULT;
+
+	if (in_compat_syscall()) {
+		struct compat_resume_swap_area swap_area;
+
+		if (copy_from_user(&swap_area, argp, sizeof(swap_area)))
+			return -EFAULT;
+		swdev = new_decode_dev(swap_area.dev);
+		offset = swap_area.offset;
+	} else {
+		struct resume_swap_area swap_area;
+
+		if (copy_from_user(&swap_area, argp, sizeof(swap_area)))
+			return -EFAULT;
+		swdev = new_decode_dev(swap_area.dev);
+		offset = swap_area.offset;
+	}
 
 	/*
 	 * User space encodes device types as two-byte values,
 	 * so we need to recode them
 	 */
-	swdev = new_decode_dev(swap_area.dev);
 	if (!swdev) {
 		data->swap = -1;
 		return -EINVAL;
 	}
-	offset = swap_area.offset;
 	data->swap = swap_type_of(swdev, offset, NULL);
 	if (data->swap < 0)
 		return -ENODEV;
@@ -394,12 +410,6 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 }
 
 #ifdef CONFIG_COMPAT
-
-struct compat_resume_swap_area {
-	compat_loff_t offset;
-	u32 dev;
-} __packed;
-
 static long
 snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
@@ -410,33 +420,13 @@ snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case SNAPSHOT_AVAIL_SWAP_SIZE:
 	case SNAPSHOT_ALLOC_SWAP_PAGE:
 	case SNAPSHOT_CREATE_IMAGE:
+	case SNAPSHOT_SET_SWAP_AREA:
 		return snapshot_ioctl(file, cmd,
 				      (unsigned long) compat_ptr(arg));
-
-	case SNAPSHOT_SET_SWAP_AREA: {
-		struct compat_resume_swap_area __user *u_swap_area =
-			compat_ptr(arg);
-		struct resume_swap_area swap_area;
-		mm_segment_t old_fs;
-		int err;
-
-		err = get_user(swap_area.offset, &u_swap_area->offset);
-		err |= get_user(swap_area.dev, &u_swap_area->dev);
-		if (err)
-			return -EFAULT;
-		old_fs = get_fs();
-		set_fs(KERNEL_DS);
-		err = snapshot_ioctl(file, SNAPSHOT_SET_SWAP_AREA,
-				     (unsigned long) &swap_area);
-		set_fs(old_fs);
-		return err;
-	}
-
 	default:
 		return snapshot_ioctl(file, cmd, arg);
 	}
 }
-
 #endif /* CONFIG_COMPAT */
 
 static const struct file_operations snapshot_fops = {
-- 
2.25.1