From: Jason Gunthorpe jgg@nvidia.com
[ Upstream commit 8ae291cc95e49011b736b641b0cfad502b7a1526 ]
The destruction flow is very complicated here because the cm_id can be destroyed from the event handler at any time if the device is hot-removed. This leaves behind a partial ctx with no cm_id in the xarray, and will let user space leak memory.
Make everything consistent in this flow in all places:
- Return the xarray back to XA_ZERO_ENTRY before beginning any destruction. The thread that reaches this first is responsible to kfree, everyone else does nothing.
- Test the xarray during the special hot-removal case to block the queue_work, this has much simpler locking and doesn't require a 'destroying'
- Fix the ref initialization so that it is only positive if cm_id != NULL, then rely on that to guide the destruction process in all cases.
Now the new ucma_destroy_private_ctx() can be called in all places that want to free the ctx, including all the error unwinds, and none of the details are missed.
Fixes: a1d33b70dbbc ("RDMA/ucma: Rework how new connections are passed through event delivery") Link: https://lore.kernel.org/r/20210105111327.230270-1-leon@kernel.org Signed-off-by: Leon Romanovsky leonro@nvidia.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/infiniband/core/ucma.c | 135 ++++++++++++++++++--------------- 1 file changed, 72 insertions(+), 63 deletions(-)
diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c index ffe2563ad3456..2cc785c1970b4 100644 --- a/drivers/infiniband/core/ucma.c +++ b/drivers/infiniband/core/ucma.c @@ -95,8 +95,6 @@ struct ucma_context { u64 uid;
struct list_head list; - /* sync between removal event and id destroy, protected by file mut */ - int destroying; struct work_struct close_work; };
@@ -122,7 +120,7 @@ static DEFINE_XARRAY_ALLOC(ctx_table); static DEFINE_XARRAY_ALLOC(multicast_table);
static const struct file_operations ucma_fops; -static int __destroy_id(struct ucma_context *ctx); +static int ucma_destroy_private_ctx(struct ucma_context *ctx);
static inline struct ucma_context *_ucma_find_context(int id, struct ucma_file *file) @@ -179,19 +177,14 @@ static void ucma_close_id(struct work_struct *work)
/* once all inflight tasks are finished, we close all underlying * resources. The context is still alive till its explicit destryoing - * by its creator. + * by its creator. This puts back the xarray's reference. */ ucma_put_ctx(ctx); wait_for_completion(&ctx->comp); /* No new events will be generated after destroying the id. */ rdma_destroy_id(ctx->cm_id);
- /* - * At this point ctx->ref is zero so the only place the ctx can be is in - * a uevent or in __destroy_id(). Since the former doesn't touch - * ctx->cm_id and the latter sync cancels this, there is no races with - * this store. - */ + /* Reading the cm_id without holding a positive ref is not allowed */ ctx->cm_id = NULL; }
@@ -204,7 +197,6 @@ static struct ucma_context *ucma_alloc_ctx(struct ucma_file *file) return NULL;
INIT_WORK(&ctx->close_work, ucma_close_id); - refcount_set(&ctx->ref, 1); init_completion(&ctx->comp); /* So list_del() will work if we don't do ucma_finish_ctx() */ INIT_LIST_HEAD(&ctx->list); @@ -218,6 +210,13 @@ static struct ucma_context *ucma_alloc_ctx(struct ucma_file *file) return ctx; }
+static void ucma_set_ctx_cm_id(struct ucma_context *ctx, + struct rdma_cm_id *cm_id) +{ + refcount_set(&ctx->ref, 1); + ctx->cm_id = cm_id; +} + static void ucma_finish_ctx(struct ucma_context *ctx) { lockdep_assert_held(&ctx->file->mut); @@ -303,7 +302,7 @@ static int ucma_connect_event_handler(struct rdma_cm_id *cm_id, ctx = ucma_alloc_ctx(listen_ctx->file); if (!ctx) goto err_backlog; - ctx->cm_id = cm_id; + ucma_set_ctx_cm_id(ctx, cm_id);
uevent = ucma_create_uevent(listen_ctx, event); if (!uevent) @@ -321,8 +320,7 @@ static int ucma_connect_event_handler(struct rdma_cm_id *cm_id, return 0;
err_alloc: - xa_erase(&ctx_table, ctx->id); - kfree(ctx); + ucma_destroy_private_ctx(ctx); err_backlog: atomic_inc(&listen_ctx->backlog); /* Returning error causes the new ID to be destroyed */ @@ -356,8 +354,12 @@ static int ucma_event_handler(struct rdma_cm_id *cm_id, wake_up_interruptible(&ctx->file->poll_wait); }
- if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL && !ctx->destroying) - queue_work(system_unbound_wq, &ctx->close_work); + if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL) { + xa_lock(&ctx_table); + if (xa_load(&ctx_table, ctx->id) == ctx) + queue_work(system_unbound_wq, &ctx->close_work); + xa_unlock(&ctx_table); + } return 0; }
@@ -461,13 +463,12 @@ static ssize_t ucma_create_id(struct ucma_file *file, const char __user *inbuf, ret = PTR_ERR(cm_id); goto err1; } - ctx->cm_id = cm_id; + ucma_set_ctx_cm_id(ctx, cm_id);
resp.id = ctx->id; if (copy_to_user(u64_to_user_ptr(cmd.response), &resp, sizeof(resp))) { - xa_erase(&ctx_table, ctx->id); - __destroy_id(ctx); + ucma_destroy_private_ctx(ctx); return -EFAULT; }
@@ -477,8 +478,7 @@ static ssize_t ucma_create_id(struct ucma_file *file, const char __user *inbuf, return 0;
err1: - xa_erase(&ctx_table, ctx->id); - kfree(ctx); + ucma_destroy_private_ctx(ctx); return ret; }
@@ -516,68 +516,73 @@ static void ucma_cleanup_mc_events(struct ucma_multicast *mc) rdma_unlock_handler(mc->ctx->cm_id); }
-/* - * ucma_free_ctx is called after the underlying rdma CM-ID is destroyed. At - * this point, no new events will be reported from the hardware. However, we - * still need to cleanup the UCMA context for this ID. Specifically, there - * might be events that have not yet been consumed by the user space software. - * mutex. After that we release them as needed. - */ -static int ucma_free_ctx(struct ucma_context *ctx) +static int ucma_cleanup_ctx_events(struct ucma_context *ctx) { int events_reported; struct ucma_event *uevent, *tmp; LIST_HEAD(list);
- ucma_cleanup_multicast(ctx); - - /* Cleanup events not yet reported to the user. */ + /* Cleanup events not yet reported to the user.*/ mutex_lock(&ctx->file->mut); list_for_each_entry_safe(uevent, tmp, &ctx->file->event_list, list) { - if (uevent->ctx == ctx || uevent->conn_req_ctx == ctx) + if (uevent->ctx != ctx) + continue; + + if (uevent->resp.event == RDMA_CM_EVENT_CONNECT_REQUEST && + xa_cmpxchg(&ctx_table, uevent->conn_req_ctx->id, + uevent->conn_req_ctx, XA_ZERO_ENTRY, + GFP_KERNEL) == uevent->conn_req_ctx) { list_move_tail(&uevent->list, &list); + continue; + } + list_del(&uevent->list); + kfree(uevent); } list_del(&ctx->list); events_reported = ctx->events_reported; mutex_unlock(&ctx->file->mut);
/* - * If this was a listening ID then any connections spawned from it - * that have not been delivered to userspace are cleaned up too. - * Must be done outside any locks. + * If this was a listening ID then any connections spawned from it that + * have not been delivered to userspace are cleaned up too. Must be done + * outside any locks. */ list_for_each_entry_safe(uevent, tmp, &list, list) { - list_del(&uevent->list); - if (uevent->resp.event == RDMA_CM_EVENT_CONNECT_REQUEST && - uevent->conn_req_ctx != ctx) - __destroy_id(uevent->conn_req_ctx); + ucma_destroy_private_ctx(uevent->conn_req_ctx); kfree(uevent); } - - mutex_destroy(&ctx->mutex); - kfree(ctx); return events_reported; }
-static int __destroy_id(struct ucma_context *ctx) +/* + * When this is called the xarray must have a XA_ZERO_ENTRY in the ctx->id (ie + * the ctx is not public to the user). This either because: + * - ucma_finish_ctx() hasn't been called + * - xa_cmpxchg() succeed to remove the entry (only one thread can succeed) + */ +static int ucma_destroy_private_ctx(struct ucma_context *ctx) { + int events_reported; + /* - * If the refcount is already 0 then ucma_close_id() has already - * destroyed the cm_id, otherwise holding the refcount keeps cm_id - * valid. Prevent queue_work() from being called. + * Destroy the underlying cm_id. New work queuing is prevented now by + * the removal from the xarray. Once the work is cancled ref will either + * be 0 because the work ran to completion and consumed the ref from the + * xarray, or it will be positive because we still have the ref from the + * xarray. This can also be 0 in cases where cm_id was never set */ - if (refcount_inc_not_zero(&ctx->ref)) { - rdma_lock_handler(ctx->cm_id); - ctx->destroying = 1; - rdma_unlock_handler(ctx->cm_id); - ucma_put_ctx(ctx); - } - cancel_work_sync(&ctx->close_work); - /* At this point it's guaranteed that there is no inflight closing task */ - if (ctx->cm_id) + if (refcount_read(&ctx->ref)) ucma_close_id(&ctx->close_work); - return ucma_free_ctx(ctx); + + events_reported = ucma_cleanup_ctx_events(ctx); + ucma_cleanup_multicast(ctx); + + WARN_ON(xa_cmpxchg(&ctx_table, ctx->id, XA_ZERO_ENTRY, NULL, + GFP_KERNEL) != NULL); + mutex_destroy(&ctx->mutex); + kfree(ctx); + return events_reported; }
static ssize_t ucma_destroy_id(struct ucma_file *file, const char __user *inbuf, @@ -596,14 +601,17 @@ static ssize_t ucma_destroy_id(struct ucma_file *file, const char __user *inbuf,
xa_lock(&ctx_table); ctx = _ucma_find_context(cmd.id, file); - if (!IS_ERR(ctx)) - __xa_erase(&ctx_table, ctx->id); + if (!IS_ERR(ctx)) { + if (__xa_cmpxchg(&ctx_table, ctx->id, ctx, XA_ZERO_ENTRY, + GFP_KERNEL) != ctx) + ctx = ERR_PTR(-ENOENT); + } xa_unlock(&ctx_table);
if (IS_ERR(ctx)) return PTR_ERR(ctx);
- resp.events_reported = __destroy_id(ctx); + resp.events_reported = ucma_destroy_private_ctx(ctx); if (copy_to_user(u64_to_user_ptr(cmd.response), &resp, sizeof(resp))) ret = -EFAULT; @@ -1777,15 +1785,16 @@ static int ucma_close(struct inode *inode, struct file *filp) * prevented by this being a FD release function. The list_add_tail() in * ucma_connect_event_handler() can run concurrently, however it only * adds to the list *after* a listening ID. By only reading the first of - * the list, and relying on __destroy_id() to block + * the list, and relying on ucma_destroy_private_ctx() to block * ucma_connect_event_handler(), no additional locking is needed. */ while (!list_empty(&file->ctx_list)) { struct ucma_context *ctx = list_first_entry( &file->ctx_list, struct ucma_context, list);
- xa_erase(&ctx_table, ctx->id); - __destroy_id(ctx); + WARN_ON(xa_cmpxchg(&ctx_table, ctx->id, ctx, XA_ZERO_ENTRY, + GFP_KERNEL) != ctx); + ucma_destroy_private_ctx(ctx); } kfree(file); return 0;