[PATCH] mm/hmm/test: Fix some copy_to_user() error handling

[Dan Carpenter <dan.carpenter@oracle.com>]

The copy_to_user() function returns the number of bytes which weren't
copied but we want to return negative error codes.  Also in dmirror_write()
if the copy_from_user() fails then there is some cleanup needed before
we can return so I fixed that as well.

Fixes: 5d5e54be8a1e3 ("mm/hmm/test: add selftest driver for HMM")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 lib/test_hmm.c | 41 +++++++++++++++++++++++++----------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 00bca6116f930..fd4889f7b3d90 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -360,9 +360,11 @@ static int dmirror_read(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 		cmd->faults++;
 	}
 
-	if (ret == 0)
-		ret = copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
-					bounce.size);
+	if (ret == 0) {
+		if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
+				 bounce.size))
+			ret = -EFAULT;
+	}
 	cmd->cpages = bounce.cpages;
 	dmirror_bounce_fini(&bounce);
 	return ret;
@@ -412,10 +414,11 @@ static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 	ret = dmirror_bounce_init(&bounce, start, size);
 	if (ret)
 		return ret;
-	ret = copy_from_user(bounce.ptr, u64_to_user_ptr(cmd->ptr),
-				bounce.size);
-	if (ret)
-		return ret;
+	if (copy_from_user(bounce.ptr, u64_to_user_ptr(cmd->ptr),
+			   bounce.size)) {
+		ret = -EFAULT;
+		goto fini;
+	}
 
 	while (1) {
 		mutex_lock(&dmirror->mutex);
@@ -431,6 +434,7 @@ static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 		cmd->faults++;
 	}
 
+fini:
 	cmd->cpages = bounce.cpages;
 	dmirror_bounce_fini(&bounce);
 	return ret;
@@ -715,9 +719,11 @@ static int dmirror_migrate(struct dmirror *dmirror,
 	mutex_lock(&dmirror->mutex);
 	ret = dmirror_do_read(dmirror, start, end, &bounce);
 	mutex_unlock(&dmirror->mutex);
-	if (ret == 0)
-		ret = copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
-					bounce.size);
+	if (ret == 0) {
+		if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
+				 bounce.size))
+			ret = -EFAULT;
+	}
 	cmd->cpages = bounce.cpages;
 	dmirror_bounce_fini(&bounce);
 	return ret;
@@ -886,9 +892,10 @@ static int dmirror_snapshot(struct dmirror *dmirror,
 			break;
 
 		n = (range.end - range.start) >> PAGE_SHIFT;
-		ret = copy_to_user(uptr, perm, n);
-		if (ret)
+		if (copy_to_user(uptr, perm, n)) {
+			ret = -EFAULT;
 			break;
+		}
 
 		cmd->cpages += n;
 		uptr += n;
@@ -911,9 +918,8 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp,
 	if (!dmirror)
 		return -EINVAL;
 
-	ret = copy_from_user(&cmd, uarg, sizeof(cmd));
-	if (ret)
-		return ret;
+	if (copy_from_user(&cmd, uarg, sizeof(cmd)))
+		return -EFAULT;
 
 	if (cmd.addr & ~PAGE_MASK)
 		return -EINVAL;
@@ -946,7 +952,10 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp,
 	if (ret)
 		return ret;
 
-	return copy_to_user(uarg, &cmd, sizeof(cmd));
+	if (copy_to_user(uarg, &cmd, sizeof(cmd)))
+		return -EFAULT;
+
+	return 0;
 }
 
 static const struct file_operations dmirror_fops = {
-- 
2.26.2