[PATCH v2 28/51] ntfs3: don't warn when a huge label is written

[Christian Brauner]

ntfs3_label_write() allocates as many bytes as are written with plain
kmalloc(). A write that is larger than what kmalloc() can hand out then
trips the page allocator's warning, which panics a panic_on_warn kernel.
Use memdup_user(), which fails such an allocation quietly with -ENOMEM
like before.

Fixes: 7832e123490a ("fs/ntfs3: Add support /proc/fs/ntfs3/<dev>/volinfo and /proc/fs/ntfs3/<dev>/label")
Cc: stable at vger.kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
---
 fs/ntfs3/super.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 29aabdc8a801..37e27b73b7a5 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -576,15 +576,10 @@ static ssize_t ntfs3_label_write(struct file *file, const char __user *buffer,
 	if (sb_rdonly(sb))
 		return -EROFS;
 
-	label = kmalloc(count, GFP_NOFS);
+	label = memdup_user(buffer, count);
+	if (IS_ERR(label))
+		return PTR_ERR(label);
 
-	if (!label)
-		return -ENOMEM;
-
-	if (copy_from_user(label, buffer, ret)) {
-		ret = -EFAULT;
-		goto out;
-	}
 	while (ret > 0 && label[ret - 1] == '\n')
 		ret -= 1;
 

-- 
2.53.0