usb: gadget: f_fs: Fix ioctl error handling

When ffs_epfile_ioctl handles FUNCTIONFS_DMABUF_* ioctls, it's currently
falling through when copy_from_user fails.

However, this fallthrough isn't being checked properly, so the handler
continues executing further than it should. It then tries the secondary
dispatch where it ultimately gives up and returns -ENOTTY.

The end result is invalid ioctl invocations will yield a -ENOTTY rather
than an -EFAULT.

It's a common pattern elsewhere in the kernel code to directly return
-EFAULT when copy_from_user fails. So we update ffs_epfile_ioctl to do
the same and fix this issue.

Signed-off-by: Sam Day <me@samcday.com>
Link: https://patch.msgid.link/20260108-ffs-dmabuf-ioctl-fix-v1-1-e51633891a81@samcday.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 6a0a4d870865ce324471004d0483898ac340371a..c479d0204afbd1cf8ff7cad2b34100351cb137da 100644 (file)
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1748,10 +1748,8 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
        {
                int fd;
 
-               if (copy_from_user(&fd, (void __user *)value, sizeof(fd))) {
-                       ret = -EFAULT;
-                       break;
-               }
+               if (copy_from_user(&fd, (void __user *)value, sizeof(fd)))
+                       return -EFAULT;
 
                return ffs_dmabuf_attach(file, fd);
        }
@@ -1759,10 +1757,8 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
        {
                int fd;
 
-               if (copy_from_user(&fd, (void __user *)value, sizeof(fd))) {
-                       ret = -EFAULT;
-                       break;
-               }
+               if (copy_from_user(&fd, (void __user *)value, sizeof(fd)))
+                       return -EFAULT;
 
                return ffs_dmabuf_detach(file, fd);
        }
@@ -1770,10 +1766,8 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
        {
                struct usb_ffs_dmabuf_transfer_req req;
 
-               if (copy_from_user(&req, (void __user *)value, sizeof(req))) {
-                       ret = -EFAULT;
-                       break;
-               }
+               if (copy_from_user(&req, (void __user *)value, sizeof(req)))
+                       return -EFAULT;
 
                return ffs_dmabuf_transfer(file, &req);
        }