[PATCH 05/31] xfs: use strndup_user in XFS_IOC_ATTRMULTI_BY_HANDLE

[Christoph Hellwig <hch@xxxxxx>]

Simplify the user copy code by using strndup_user.  This means that we
now do one memory allocation per operation instead of one per ioctl,
but memory allocations are cheap compared to the actual file system
operations.  Also the error for an invalid path is now EINVAL or EFAULT
instead of the previous odd and undocumented ERANGE.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Chandan Rajendra <chandanrlinux@xxxxxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
 fs/xfs/xfs_ioctl.c   | 17 +++++------------
 fs/xfs/xfs_ioctl32.c | 17 +++++------------
 2 files changed, 10 insertions(+), 24 deletions(-)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index b806003caacd..bb490a954c0b 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -448,11 +448,6 @@ xfs_attrmulti_by_handle(
 		goto out_dput;
 	}
 
-	error = -ENOMEM;
-	attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
-	if (!attr_name)
-		goto out_kfree_ops;
-
 	error = 0;
 	for (i = 0; i < am_hreq.opcount; i++) {
 		if ((ops[i].am_flags & ATTR_ROOT) &&
@@ -462,12 +457,11 @@ xfs_attrmulti_by_handle(
 		}
 		ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;
 
-		ops[i].am_error = strncpy_from_user((char *)attr_name,
-				ops[i].am_attrname, MAXNAMELEN);
-		if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
-			error = -ERANGE;
-		if (ops[i].am_error < 0)
+		attr_name = strndup_user(ops[i].am_attrname, MAXNAMELEN);
+		if (IS_ERR(attr_name)) {
+			ops[i].am_error = PTR_ERR(attr_name);
 			break;
+		}
 
 		switch (ops[i].am_opcode) {
 		case ATTR_OP_GET:
@@ -498,13 +492,12 @@ xfs_attrmulti_by_handle(
 		default:
 			ops[i].am_error = -EINVAL;
 		}
+		kfree(attr_name);
 	}
 
 	if (copy_to_user(am_hreq.ops, ops, size))
 		error = -EFAULT;
 
-	kfree(attr_name);
- out_kfree_ops:
 	kfree(ops);
  out_dput:
 	dput(dentry);
diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
index e085f304e539..936c2f62fb6c 100644
--- a/fs/xfs/xfs_ioctl32.c
+++ b/fs/xfs/xfs_ioctl32.c
@@ -445,11 +445,6 @@ xfs_compat_attrmulti_by_handle(
 		goto out_dput;
 	}
 
-	error = -ENOMEM;
-	attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
-	if (!attr_name)
-		goto out_kfree_ops;
-
 	error = 0;
 	for (i = 0; i < am_hreq.opcount; i++) {
 		if ((ops[i].am_flags & ATTR_ROOT) &&
@@ -459,13 +454,12 @@ xfs_compat_attrmulti_by_handle(
 		}
 		ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;
 
-		ops[i].am_error = strncpy_from_user((char *)attr_name,
-				compat_ptr(ops[i].am_attrname),
+		attr_name = strndup_user(compat_ptr(ops[i].am_attrname),
 				MAXNAMELEN);
-		if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
-			error = -ERANGE;
-		if (ops[i].am_error < 0)
+		if (IS_ERR(attr_name)) {
+			ops[i].am_error = PTR_ERR(attr_name);
 			break;
+		}
 
 		switch (ops[i].am_opcode) {
 		case ATTR_OP_GET:
@@ -496,13 +490,12 @@ xfs_compat_attrmulti_by_handle(
 		default:
 			ops[i].am_error = -EINVAL;
 		}
+		kfree(attr_name);
 	}
 
 	if (copy_to_user(compat_ptr(am_hreq.ops), ops, size))
 		error = -EFAULT;
 
-	kfree(attr_name);
- out_kfree_ops:
 	kfree(ops);
  out_dput:
 	dput(dentry);
-- 
2.24.1