[PATCH 6.18 342/752] usb: gadget: f_fs: Fix ioctl error handling

Sasha Levin
2026-02-28T17:52:54Z

From: Sam Day <me@samcday.com>

[ Upstream commit 8e4c1d06183c25022f6b0002a5cab84979ca6337 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/usb/gadget/function/f_fs.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 2061c38d772ca..497d20260b040 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1724,10 +1724,8 @@ 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);
}
@@ -1735,10 +1733,8 @@ 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);
}
@@ -1746,10 +1742,8 @@ 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);
}
--
2.51.0