From d1e09f304a1d9651c5059ebfeb696dc2effc9b32 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Sun, 3 Jul 2016 15:28:18 +0300 Subject: [PATCH] IB/uverbs: Fix race between uverbs_close and remove_one 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 Signed-off-by: Jason Gunthorpe Signed-off-by: Yishai Hadas Signed-off-by: Leon Romanovsky Signed-off-by: Doug Ledford --- drivers/infiniband/core/uverbs.h | 1 + drivers/infiniband/core/uverbs_main.c | 37 +++++++++++++++++---------- 2 files changed, 25 insertions(+), 13 deletions(-) diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h index 612ccfd39bf9..9245e55debed 100644 --- 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; diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c index 31f422a70623..09d515763ad6 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -931,6 +931,7 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp) 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); @@ -956,18 +957,20 @@ static int ib_uverbs_close(struct inode *inode, struct file *filp) { 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); @@ -1181,22 +1184,30 @@ static void ib_uverbs_free_hw_resources(struct ib_uverbs_device *uverbs_dev, 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); } -- 2.30.2