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Subject[PATCH 4.4 022/118] IB/uverbs: Fix race between uverbs_close and remove_one
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>

commit d1e09f304a1d9651c5059ebfeb696dc2effc9b32 upstream.

Fixes an oops that might happen if uverbs_close races with
remove_one.

Both contexts may run ib_uverbs_cleanup_ucontext, it depends
on the flow.

Currently, there is no protection for a case that remove_one
didn't make the cleanup it runs to its end, the underlying
ib_device was freed then uverbs_close will call
ib_uverbs_cleanup_ucontext and OOPs.

Above might happen if uverbs_close deleted the file from the list
then remove_one didn't find it and runs to its end.

Fixes to protect against that case by a new cleanup lock so that
ib_uverbs_cleanup_ucontext will be called always before that
remove_one is ended.

Fixes: 35d4a0b63dc0 ("IB/uverbs: Fix race between ib_uverbs_open and remove_one")
Reported-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/infiniband/core/uverbs.h | 1
drivers/infiniband/core/uverbs_main.c | 37 ++++++++++++++++++++++------------
2 files changed, 25 insertions(+), 13 deletions(-)

--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -116,6 +116,7 @@ struct ib_uverbs_event_file {
struct ib_uverbs_file {
struct kref ref;
struct mutex mutex;
+ struct mutex cleanup_mutex; /* protect cleanup */
struct ib_uverbs_device *device;
struct ib_ucontext *ucontext;
struct ib_event_handler event_handler;
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -922,6 +922,7 @@ static int ib_uverbs_open(struct inode *
file->async_file = NULL;
kref_init(&file->ref);
mutex_init(&file->mutex);
+ mutex_init(&file->cleanup_mutex);

filp->private_data = file;
kobject_get(&dev->kobj);
@@ -947,18 +948,20 @@ static int ib_uverbs_close(struct inode
{
struct ib_uverbs_file *file = filp->private_data;
struct ib_uverbs_device *dev = file->device;
- struct ib_ucontext *ucontext = NULL;
+
+ mutex_lock(&file->cleanup_mutex);
+ if (file->ucontext) {
+ ib_uverbs_cleanup_ucontext(file, file->ucontext);
+ file->ucontext = NULL;
+ }
+ mutex_unlock(&file->cleanup_mutex);

mutex_lock(&file->device->lists_mutex);
- ucontext = file->ucontext;
- file->ucontext = NULL;
if (!file->is_closed) {
list_del(&file->list);
file->is_closed = 1;
}
mutex_unlock(&file->device->lists_mutex);
- if (ucontext)
- ib_uverbs_cleanup_ucontext(file, ucontext);

if (file->async_file)
kref_put(&file->async_file->ref, ib_uverbs_release_event_file);
@@ -1172,22 +1175,30 @@ static void ib_uverbs_free_hw_resources(
mutex_lock(&uverbs_dev->lists_mutex);
while (!list_empty(&uverbs_dev->uverbs_file_list)) {
struct ib_ucontext *ucontext;
-
file = list_first_entry(&uverbs_dev->uverbs_file_list,
struct ib_uverbs_file, list);
file->is_closed = 1;
- ucontext = file->ucontext;
list_del(&file->list);
- file->ucontext = NULL;
kref_get(&file->ref);
mutex_unlock(&uverbs_dev->lists_mutex);
- /* We must release the mutex before going ahead and calling
- * disassociate_ucontext. disassociate_ucontext might end up
- * indirectly calling uverbs_close, for example due to freeing
- * the resources (e.g mmput).
- */
+
ib_uverbs_event_handler(&file->event_handler, &event);
+
+ mutex_lock(&file->cleanup_mutex);
+ ucontext = file->ucontext;
+ file->ucontext = NULL;
+ mutex_unlock(&file->cleanup_mutex);
+
+ /* At this point ib_uverbs_close cannot be running
+ * ib_uverbs_cleanup_ucontext
+ */
if (ucontext) {
+ /* We must release the mutex before going ahead and
+ * calling disassociate_ucontext. disassociate_ucontext
+ * might end up indirectly calling uverbs_close,
+ * for example due to freeing the resources
+ * (e.g mmput).
+ */
ib_dev->disassociate_ucontext(ucontext);
ib_uverbs_cleanup_ucontext(file, ucontext);
}

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