Patch "xdp: Move the rxq_info.mem clearing to unreg_mem_model()" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xdp-move-the-rxq_info.mem-clearing-to-unreg_mem_mode.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 800d5efeaa4819009642d2fec8c039672e68cde7
Author: Jakub Kicinski <kuba@xxxxxxxxxx>
Date:   Fri Jun 25 15:16:12 2021 -0700

    xdp: Move the rxq_info.mem clearing to unreg_mem_model()
    
    [ Upstream commit a78cae2476812cecaa4a33d0086bbb53986906bc ]
    
    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@xxxxxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20210625221612.2637086-1-kuba@xxxxxxxxxx
    Stable-dep-of: 7e9f79428372 ("xdp: Remove WARN() from __xdp_reg_mem_model()")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/core/xdp.c b/net/core/xdp.c
index b8d7fa47d293c..0f0b65981614b 100644
--- 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);