[PATCH 3.4 081/172] gadgetfs: use-after-free in ->aio_read()

lizf
2015-06-16T09:18:44Z

From: Al Viro <viro@zeniv.linux.org.uk>

3.4.108-rc1 review patch. If anyone has any objections, please let me know.

------------------

commit f01d35a15fa04162a58b95970fc01fa70ec9dacd upstream.

AIO_PREAD requests call ->aio_read() with iovec on caller's stack, so if
we are going to access it asynchronously, we'd better get ourselves
a copy - the one on kernel stack of aio_run_iocb() won't be there
anymore. function/f_fs.c take care of doing that, legacy/inode.c
doesn't...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[lizf: Backproted to 3.4:
- adjust context
- need kfree() after calling get_ready_ep()]
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
drivers/usb/gadget/inode.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index d9eaaa3..093e907 100644
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -570,6 +570,7 @@ static ssize_t ep_aio_read_retry(struct kiocb *iocb)
break;
}
kfree(priv->buf);
+ kfree(priv->iv);
kfree(priv);
return len;
}
@@ -591,6 +592,7 @@ static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
*/
if (priv->iv == NULL || unlikely(req->actual == 0)) {
kfree(req->buf);
+ kfree(priv->iv);
kfree(priv);
iocb->private = NULL;
/* aio_complete() reports bytes-transferred _and_ faults */
@@ -626,7 +628,7 @@ ep_aio_rwtail(
struct usb_request *req;
ssize_t value;

- priv = kmalloc(sizeof *priv, GFP_KERNEL);
+ priv = kzalloc(sizeof *priv, GFP_KERNEL);
if (!priv) {
value = -ENOMEM;
fail:
@@ -634,11 +636,19 @@ fail:
return value;
}
iocb->private = priv;
- priv->iv = iv;
+ if (iv) {
+ priv->iv = kmemdup(iv, nr_segs * sizeof(struct iovec),
+ GFP_KERNEL);
+ if (!priv->iv) {
+ kfree(priv);
+ goto fail;
+ }
+ }
priv->nr_segs = nr_segs;

value = get_ready_ep(iocb->ki_filp->f_flags, epdata);
if (unlikely(value < 0)) {
+ kfree(priv->iv);
kfree(priv);
goto fail;
}
@@ -672,6 +682,7 @@ fail:
mutex_unlock(&epdata->lock);

if (unlikely(value)) {
+ kfree(priv->iv);
kfree(priv);
put_ep(epdata);
} else
--
1.9.1