[v2] usb: gadget: f_fs: Invalidate io_data when USB request is dequeued or interrupted

Commit Message

Frode Isaksen March 31, 2025, 8:53 a.m. UTC

From: Frode Isaksen <[e-mail]>

Invalidate io_data by setting context to NULL when USB request is
dequeued or interrupted, and check for NULL io_data in epfile_io_complete().
The invalidation of io_data in req->context is done when exiting
epfile_io(), since then io_data will become invalid as it is allocated
on the stack.
The epfile_io_complete() may be called after ffs_epfile_io() returns
in case the wait_for_completion_interruptible() is interrupted.
This fixes a use-after-free error with the following call stack:

Unable to handle kernel paging request at virtual address ffffffc02f7bbcc0
pc : ffs_epfile_io_complete+0x30/0x48
lr : usb_gadget_giveback_request+0x30/0xf8
Call trace:
ffs_epfile_io_complete+0x30/0x48
usb_gadget_giveback_request+0x30/0xf8
dwc3_remove_requests+0x264/0x2e8
dwc3_gadget_pullup+0x1d0/0x250
kretprobe_trampoline+0x0/0xc4
usb_gadget_remove_driver+0x40/0xf4
usb_gadget_unregister_driver+0xdc/0x178
unregister_gadget_item+0x40/0x6c
ffs_closed+0xd4/0x10c
ffs_data_clear+0x2c/0xf0
ffs_data_closed+0x178/0x1ec
ffs_ep0_release+0x24/0x38
__fput+0xe8/0x27c

Signed-off-by: Frode Isaksen <[e-mail]>
Cc: [e-mail]
---
v1 -> v2:
Removed WARN_ON() in ffs_epfile_io_complete().
Clarified commit message.
Added stable Cc tag.

 drivers/usb/gadget/function/f_fs.c | 5 +++++
 1 file changed, 5 insertions(+)

Patch

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 2dea9e42a0f8..e35d32e7be58 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -738,6 +738,9 @@  static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
 {
 	struct ffs_io_data *io_data = req->context;
 
+	if (io_data == NULL)
+		return;
+
 	if (req->status)
 		io_data->status = req->status;
 	else
@@ -1126,6 +1129,7 @@  static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 			spin_lock_irq(&epfile->ffs->eps_lock);
 			if (epfile->ep != ep) {
 				ret = -ESHUTDOWN;
+				req->context = NULL;
 				goto error_lock;
 			}
 			/*
@@ -1140,6 +1144,7 @@  static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 			interrupted = io_data->status < 0;
 		}
 
+		req->context = NULL;
 		if (interrupted)
 			ret = -EINTR;
 		else if (io_data->read && io_data->status > 0)