xdp: Move the rxq_info.mem clearing to unreg_mem_model()

xdp_rxq_info_unreg() implicitly calls xdp_rxq_info_unreg_mem_model().
This may well be confusing to the driver authors, and lead to double free
if they call xdp_rxq_info_unreg_mem_model() before xdp_rxq_info_unreg()
(when mem model type == MEM_TYPE_PAGE_POOL).

In fact error path of mvpp2_rxq_init() seems to currently do exactly that.

The double free will result in refcount underflow in page_pool_destroy().
Make the interface a little more programmer friendly by clearing type and
id so that xdp_rxq_info_unreg_mem_model() can be called multiple times.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210625221612.2637086-1-kuba@kernel.org

diff --git a/net/core/xdp.c b/net/core/xdp.c
index 725d20f..cc92ccb 100644 (file)
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -113,8 +113,13 @@ static void mem_allocator_disconnect(void *allocator)
 void xdp_rxq_info_unreg_mem_model(struct xdp_rxq_info *xdp_rxq)
 {
        struct xdp_mem_allocator *xa;
+       int type = xdp_rxq->mem.type;
        int id = xdp_rxq->mem.id;
 
+       /* Reset mem info to defaults */
+       xdp_rxq->mem.id = 0;
+       xdp_rxq->mem.type = 0;
+
        if (xdp_rxq->reg_state != REG_STATE_REGISTERED) {
                WARN(1, "Missing register, driver bug");
                return;
@@ -123,7 +128,7 @@ void xdp_rxq_info_unreg_mem_model(struct xdp_rxq_info *xdp_rxq)
        if (id == 0)
                return;
 
-       if (xdp_rxq->mem.type == MEM_TYPE_PAGE_POOL) {
+       if (type == MEM_TYPE_PAGE_POOL) {
                rcu_read_lock();
                xa = rhashtable_lookup(mem_id_ht, &id, mem_id_rht_params);
                page_pool_destroy(xa->page_pool);
@@ -144,10 +149,6 @@ void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq)
 
        xdp_rxq->reg_state = REG_STATE_UNREGISTERED;
        xdp_rxq->dev = NULL;
-
-       /* Reset mem info to defaults */
-       xdp_rxq->mem.id = 0;
-       xdp_rxq->mem.type = 0;
 }
 EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg);