activate_ep_files() allocates a bunch of ep_data, creates inodes and
dentries for them and sticks them into a cyclic list. inode->u.generic_ip
is set to created ep_data, refcount is 1.
destroy_ep_files() goes through that cyclic list, gets dentry from each
ep_data on it and drops ep_data. Then it kills dentry and inode by
/* break link to dcache */
mutex_lock (&parent->i_mutex);
d_delete (dentry);
dput (dentry);
mutex_unlock (&parent->i_mutex);
Tries to kill, anyway. The thing is, ep_open() (->open() on that sucker)
does
static int
ep_open (struct inode *inode, struct file *fd)
{
struct ep_data *data = inode->u.generic_ip;
int value = -EBUSY;
if (down_interruptible (&data->lock) != 0)
return -EINTR;
followed eventually by pinning data (i.e. ep_data for that inode) down.
It's way too late - by the time we enter ep_open(), inode->u.generic_ip
might be already pointing to freed memory.
AFAICS, the cheapest way to deal with that would be to set ->u.generic_ip
to NULL before dropping ep_data in ep_destroy_files(), have that done
under global spinlock and have ep_open() et.al. start with checking if
the pointer is NULL under the same spinlock and grabbing a reference if
it isn't.
There's another question: opened files are opened; what protects them
from gadgetfs_unbind() freeing ep->req while ep is still pinned down
by an opened file? We do not hold dev->lock or ep->lock there...
One more: what protects dev->state? I don't see any lock that would
be held over all places that modify it.
Oh, and a trivial leak fix, while we are at it:
Subject: [PATCH] fix leak in activate_ep_files()
Signed-off-by: Al Viro <[email protected]>
---
drivers/usb/gadget/inode.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
676113fa9fe777d13904017f8da5ae04c214567f
diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index 42b4570..0eb010a 100644
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -1614,6 +1614,7 @@ static int activate_ep_files (struct dev
data, &ep_config_operations,
&data->dentry);
if (!data->inode) {
+ usb_ep_free_request(ep, data->req);
kfree (data);
goto enomem;
}
--
1.3.0.g0080f
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