]> asedeno.scripts.mit.edu Git - linux.git/commitdiff
IB/uverbs: Fix locking around struct ib_uverbs_file ucontext
authorJason Gunthorpe <jgg@mellanox.com>
Tue, 10 Jul 2018 19:43:06 +0000 (13:43 -0600)
committerJason Gunthorpe <jgg@mellanox.com>
Wed, 25 Jul 2018 20:21:46 +0000 (14:21 -0600)
We have a parallel unlocked reader and writer with ib_uverbs_get_context()
vs everything else, and nothing guarantees this works properly.

Audit and fix all of the places that access ucontext to use one of the
following locking schemes:
- Call ib_uverbs_get_ucontext() under SRCU and check for failure
- Access the ucontext through an struct ib_uobject context member
  while holding a READ or WRITE lock on the uobject.
  This value cannot be NULL and has no race.
- Hold the ucontext_lock and check for ufile->ucontext !NULL

This also re-implements ib_uverbs_get_ucontext() in a way that is safe
against concurrent ib_uverbs_get_context() and disassociation.

As a side effect, every access to ucontext in the commands is via
ib_uverbs_get_context() with an error check, or via the uobject, so there
is no longer any need for the core code to check ucontext on every command
call. These checks are also removed.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
drivers/infiniband/core/rdma_core.c
drivers/infiniband/core/uverbs.h
drivers/infiniband/core/uverbs_cmd.c
drivers/infiniband/core/uverbs_ioctl.c
drivers/infiniband/core/uverbs_main.c
drivers/infiniband/core/uverbs_std_types_cq.c
drivers/infiniband/core/uverbs_std_types_dm.c
drivers/infiniband/hw/mlx5/devx.c
include/rdma/uverbs_ioctl.h

index 8a6ce66d4726f52521432e48e4f321bcef75c5af..a63844ba84144949f99164e16966beffce2b6ae8 100644 (file)
@@ -154,8 +154,14 @@ int __uobj_perform_destroy(const struct uverbs_obj_type *type, u32 id,
 static struct ib_uobject *alloc_uobj(struct ib_uverbs_file *ufile,
                                     const struct uverbs_obj_type *type)
 {
-       struct ib_uobject *uobj = kzalloc(type->obj_size, GFP_KERNEL);
+       struct ib_uobject *uobj;
+       struct ib_ucontext *ucontext;
+
+       ucontext = ib_uverbs_get_ucontext(ufile);
+       if (IS_ERR(ucontext))
+               return ERR_CAST(ucontext);
 
+       uobj = kzalloc(type->obj_size, GFP_KERNEL);
        if (!uobj)
                return ERR_PTR(-ENOMEM);
        /*
@@ -163,7 +169,7 @@ static struct ib_uobject *alloc_uobj(struct ib_uverbs_file *ufile,
         * The object is added to the list in the commit stage.
         */
        uobj->ufile = ufile;
-       uobj->context = ufile->ucontext;
+       uobj->context = ucontext;
        INIT_LIST_HEAD(&uobj->list);
        uobj->type = type;
        /*
@@ -309,7 +315,7 @@ static struct ib_uobject *alloc_begin_idr_uobject(const struct uverbs_obj_type *
        if (ret)
                goto uobj_put;
 
-       ret = ib_rdmacg_try_charge(&uobj->cg_obj, ufile->ucontext->device,
+       ret = ib_rdmacg_try_charge(&uobj->cg_obj, uobj->context->device,
                                   RDMACG_RESOURCE_HCA_OBJECT);
        if (ret)
                goto idr_remove;
@@ -761,7 +767,7 @@ static void ufile_destroy_ucontext(struct ib_uverbs_file *ufile,
         * FIXME: Drivers are not permitted to fail dealloc_ucontext, remove
         * the error return.
         */
-       ret = ucontext->device->dealloc_ucontext(ufile->ucontext);
+       ret = ucontext->device->dealloc_ucontext(ucontext);
        WARN_ON(ret);
 
        ufile->ucontext = NULL;
index ca9b0450d3f90089cb86b7a2cbd35995ede65424..cf02b433000c0338b5c425cefd4956e95f140995 100644 (file)
@@ -137,8 +137,11 @@ struct ib_uverbs_completion_event_file {
 struct ib_uverbs_file {
        struct kref                             ref;
        struct ib_uverbs_device                *device;
-       /* Protects writing to ucontext */
        struct mutex                            ucontext_lock;
+       /*
+        * ucontext must be accessed via ib_uverbs_get_ucontext() or with
+        * ucontext_lock held
+        */
        struct ib_ucontext                     *ucontext;
        struct ib_event_handler                 event_handler;
        struct ib_uverbs_async_event_file       *async_file;
index 73b563edb5877f32d4a6c8bf22fb0ed075672be9..38d7de3f9b2f903bb59008ee7b0b0a758ce4d5e7 100644 (file)
@@ -146,10 +146,14 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
                goto err_file;
        }
 
-       file->ucontext = ucontext;
-
        fd_install(resp.async_fd, filp);
 
+       /*
+        * Make sure that ib_uverbs_get_ucontext() sees the pointer update
+        * only after all writes to setup the ucontext have completed
+        */
+       smp_store_release(&file->ucontext, ucontext);
+
        mutex_unlock(&file->ucontext_lock);
 
        return in_len;
@@ -350,7 +354,7 @@ ssize_t ib_uverbs_alloc_pd(struct ib_uverbs_file *file,
        if (IS_ERR(uobj))
                return PTR_ERR(uobj);
 
-       pd = ib_dev->alloc_pd(ib_dev, file->ucontext, &udata);
+       pd = ib_dev->alloc_pd(ib_dev, uobj->context, &udata);
        if (IS_ERR(pd)) {
                ret = PTR_ERR(pd);
                goto err;
@@ -538,7 +542,7 @@ ssize_t ib_uverbs_open_xrcd(struct ib_uverbs_file *file,
        }
 
        if (!xrcd) {
-               xrcd = ib_dev->alloc_xrcd(ib_dev, file->ucontext, &udata);
+               xrcd = ib_dev->alloc_xrcd(ib_dev, obj->uobject.context, &udata);
                if (IS_ERR(xrcd)) {
                        ret = PTR_ERR(xrcd);
                        goto err;
@@ -1004,7 +1008,7 @@ static struct ib_ucq_object *create_cq(struct ib_uverbs_file *file,
        if (cmd_sz > offsetof(typeof(*cmd), flags) + sizeof(cmd->flags))
                attr.flags = cmd->flags;
 
-       cq = ib_dev->create_cq(ib_dev, &attr, file->ucontext, uhw);
+       cq = ib_dev->create_cq(ib_dev, &attr, obj->uobject.context, uhw);
        if (IS_ERR(cq)) {
                ret = PTR_ERR(cq);
                goto err_file;
index 26ddc5cadcdbbf8cf0bf2ad5698614e4a4021f77..db7a92ea5dbe8783c2c036ddad49bfa20424b970 100644 (file)
@@ -140,7 +140,7 @@ static int uverbs_process_attr(struct ib_uverbs_file *ufile,
                if (uattr->attr_data.reserved)
                        return -EINVAL;
 
-               if (uattr->len != 0 || !ufile->ucontext)
+               if (uattr->len != 0)
                        return -EINVAL;
 
                o_attr = &e->obj_attr;
@@ -373,9 +373,6 @@ static long ib_uverbs_cmd_verbs(struct ib_device *ib_dev,
        if (!method_spec)
                return -EPROTONOSUPPORT;
 
-       if ((method_spec->flags & UVERBS_ACTION_FLAG_CREATE_ROOT) ^ !file->ucontext)
-               return -EINVAL;
-
        ctx_size = sizeof(*ctx) +
                   sizeof(struct uverbs_attr_bundle) +
                   sizeof(struct uverbs_attr_bundle_hash) * method_spec->num_buckets +
index 78d79020ea5c384f8f155a183b82ebdb547018ba..34df04ed142be722527be12398a8fe25e1857370 100644 (file)
@@ -136,9 +136,27 @@ static int (*uverbs_ex_cmd_table[])(struct ib_uverbs_file *file,
 static void ib_uverbs_add_one(struct ib_device *device);
 static void ib_uverbs_remove_one(struct ib_device *device, void *client_data);
 
+/*
+ * Must be called with the ufile->device->disassociate_srcu held, and the lock
+ * must be held until use of the ucontext is finished.
+ */
 struct ib_ucontext *ib_uverbs_get_ucontext(struct ib_uverbs_file *ufile)
 {
-       return ufile->ucontext;
+       /*
+        * We do not hold the hw_destroy_rwsem lock for this flow, instead
+        * srcu is used. It does not matter if someone races this with
+        * get_context, we get NULL or valid ucontext.
+        */
+       struct ib_ucontext *ucontext = smp_load_acquire(&ufile->ucontext);
+
+       if (!srcu_dereference(ufile->device->ib_dev,
+                             &ufile->device->disassociate_srcu))
+               return ERR_PTR(-EIO);
+
+       if (!ucontext)
+               return ERR_PTR(-EINVAL);
+
+       return ucontext;
 }
 EXPORT_SYMBOL(ib_uverbs_get_ucontext);
 
@@ -729,10 +747,6 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
        if (ret)
                return ret;
 
-       if (!file->ucontext &&
-           (command != IB_USER_VERBS_CMD_GET_CONTEXT || extended))
-               return -EINVAL;
-
        if (extended) {
                if (count < (sizeof(hdr) + sizeof(ex_hdr)))
                        return -EINVAL;
@@ -791,22 +805,18 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
 {
        struct ib_uverbs_file *file = filp->private_data;
-       struct ib_device *ib_dev;
+       struct ib_ucontext *ucontext;
        int ret = 0;
        int srcu_key;
 
        srcu_key = srcu_read_lock(&file->device->disassociate_srcu);
-       ib_dev = srcu_dereference(file->device->ib_dev,
-                                 &file->device->disassociate_srcu);
-       if (!ib_dev) {
-               ret = -EIO;
+       ucontext = ib_uverbs_get_ucontext(file);
+       if (IS_ERR(ucontext)) {
+               ret = PTR_ERR(ucontext);
                goto out;
        }
 
-       if (!file->ucontext)
-               ret = -ENODEV;
-       else
-               ret = ib_dev->mmap(file->ucontext, vma);
+       ret = ucontext->device->mmap(ucontext, vma);
 out:
        srcu_read_unlock(&file->device->disassociate_srcu, srcu_key);
        return ret;
index 5a6154345fa043167263001665b9e4de435497f2..c71305fc043332edb3ab74601394fb238d1fad11 100644 (file)
@@ -113,7 +113,7 @@ static int UVERBS_HANDLER(UVERBS_METHOD_CQ_CREATE)(struct ib_device *ib_dev,
        /* Temporary, only until drivers get the new uverbs_attr_bundle */
        create_udata(attrs, &uhw);
 
-       cq = ib_dev->create_cq(ib_dev, &attr, file->ucontext, &uhw);
+       cq = ib_dev->create_cq(ib_dev, &attr, obj->uobject.context, &uhw);
        if (IS_ERR(cq)) {
                ret = PTR_ERR(cq);
                goto err_event_file;
index 9e148e322523d5db1eb5f60e08552d96a0951c89..c90efa4b99f4e26c7168a7c062a36c6a1622221b 100644 (file)
@@ -70,7 +70,7 @@ static int UVERBS_HANDLER(UVERBS_METHOD_DM_ALLOC)(struct ib_device *ib_dev,
 
        uobj = uverbs_attr_get(attrs, UVERBS_ATTR_ALLOC_DM_HANDLE)->obj_attr.uobject;
 
-       dm = ib_dev->alloc_dm(ib_dev, file->ucontext, &attr, attrs);
+       dm = ib_dev->alloc_dm(ib_dev, uobj->context, &attr, attrs);
        if (IS_ERR(dm))
                return PTR_ERR(dm);
 
index 98b1575226c1b477c64c991f2e7ed5c5984fa819..fee800f2fdec9f24e450642114880759ec7f4d6a 100644 (file)
@@ -458,16 +458,21 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_QUERY_UAR)(struct ib_device *ib_de
                                  struct ib_uverbs_file *file,
                                  struct uverbs_attr_bundle *attrs)
 {
-       struct mlx5_ib_ucontext *c = devx_ufile2uctx(file);
+       struct mlx5_ib_ucontext *c;
+       struct mlx5_ib_dev *dev;
        u32 user_idx;
        s32 dev_idx;
 
+       c = devx_ufile2uctx(file);
+       if (IS_ERR(c))
+               return PTR_ERR(c);
+       dev = to_mdev(c->ibucontext.device);
+
        if (uverbs_copy_from(&user_idx, attrs,
                             MLX5_IB_ATTR_DEVX_QUERY_UAR_USER_IDX))
                return -EFAULT;
 
-       dev_idx = bfregn_to_uar_index(to_mdev(ib_dev),
-                                     &c->bfregi, user_idx, true);
+       dev_idx = bfregn_to_uar_index(dev, &c->bfregi, user_idx, true);
        if (dev_idx < 0)
                return dev_idx;
 
@@ -482,8 +487,8 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_OTHER)(struct ib_device *ib_dev,
                                  struct ib_uverbs_file *file,
                                  struct uverbs_attr_bundle *attrs)
 {
-       struct mlx5_ib_ucontext *c = devx_ufile2uctx(file);
-       struct mlx5_ib_dev *dev = to_mdev(ib_dev);
+       struct mlx5_ib_ucontext *c;
+       struct mlx5_ib_dev *dev;
        void *cmd_in = uverbs_attr_get_alloced_ptr(
                attrs, MLX5_IB_ATTR_DEVX_OTHER_CMD_IN);
        int cmd_out_len = uverbs_attr_get_len(attrs,
@@ -491,6 +496,11 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_OTHER)(struct ib_device *ib_dev,
        void *cmd_out;
        int err;
 
+       c = devx_ufile2uctx(file);
+       if (IS_ERR(c))
+               return PTR_ERR(c);
+       dev = to_mdev(c->ibucontext.device);
+
        if (!c->devx_uid)
                return -EPERM;
 
index 7f230d1ec2b8b2fed2e0958137043d1e22ca4385..d16d31d4322d4fe4928f03930154fd293f843721 100644 (file)
@@ -123,14 +123,6 @@ struct uverbs_attr_spec_hash {
 struct uverbs_attr_bundle;
 struct ib_uverbs_file;
 
-enum {
-       /*
-        * Action marked with this flag creates a context (or root for all
-        * objects).
-        */
-       UVERBS_ACTION_FLAG_CREATE_ROOT = 1U << 0,
-};
-
 struct uverbs_method_spec {
        /* Combination of bits from enum UVERBS_ACTION_FLAG_XXXX */
        u32                                             flags;