FAILED: patch "[PATCH] ieee802154: hwsim: serialize pib updates to fix double-free" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 979d5b8de8ed4e1f997aef12da5694b99be7b871
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026091659-marry-gender-6432@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 979d5b8de8ed4e1f997aef12da5694b99be7b871 Mon Sep 17 00:00:00 2001
From: David Carlier <[email protected]>
Date: Thu, 9 Jul 2026 23:18:58 +0100
Subject: [PATCH] ieee802154: hwsim: serialize pib updates to fix double-free

hwsim_update_pib() does an unserialized read-swap-free of phy->pib:

	pib_old = rtnl_dereference(phy->pib);
	...
	rcu_assign_pointer(phy->pib, pib);
	kfree_rcu(pib_old, rcu);

It assumes the RTNL is held, but ->set_channel is not always called under it: the mac802154 scan worker changes channels via drv_set_channel() without the RTNL. Such an update can race an RTNL-held one on the same phy; both read the same pib_old and both kfree_rcu() it, double-freeing the object. With SLUB percpu sheaves batching kfree_rcu(), this surfaces as a KASAN invalid-free in rcu_free_sheaf().

struct hwsim_phy has no lock for pib. Add one and make the swap atomic with rcu_replace_pointer() under it, dropping the misleading rtnl_dereference().

index 6daa0f198b9f..a9bd1555d2dc 100644
@@ -72,6 +72,8 @@ struct hwsim_phy {
 	struct ieee802154_hw *hw;
 	u32 idx;
 
+	/* Serializes phy->pib_updates. */
+	spinlock_t pib_lock;
 	struct hwsim_pib __rcu *pib;
 
 	bool suspended;

@@ -102,8 +104,6 @@ static int hwsim_update_pib(struct ieee802154_hw *hw, u8 page, u8 channel,
 	if (!pib)
 		return -ENOMEM;
 
-	pib_old = rtnl_dereference(phy->pib);
-
 	pib->page = page;
 	pib->channel = channel;
 	pib->filt.short_addr = filt->short_addr;

@@ -112,7 +112,10 @@ static int hwsim_update_pib(struct ieee802154_hw *hw, u8 page, u8 channel,
 	pib->filt.pan_coord = filt->pan_coord;
 	pib->filt_level = filt_level;
 
-	rcu_assign_pointer(phy->pib, pib);
+	spin_lock_bh(&phy->pib_lock);
+	pib_old = rcu_replace_pointer(phy->pib, pib,
+				      lockdep_is_held(&phy->pib_lock));
+	spin_unlock_bh(&phy->pib_lock);
 	kfree_rcu(pib_old, rcu);
 	return 0;
 }

@@ -952,6 +955,7 @@ static int hwsim_add_one(struct genl_info *info, struct device *dev,
 		goto err_pib;
 	}
 
+	spin_lock_init(&phy->pib_lock);
 	pib->channel = 13;
 	pib->filt.short_addr = cpu_to_le16(IEEE802154_ADDR_BROADCAST);
 	pib->filt.pan_id = cpu_to_le16(IEEE802154_PANID_BROADCAST);

From: David Carlier <[email protected]>

[ Upstream commit 979d5b8de8ed4e1f997aef12da5694b99be7b871 ]

hwsim_update_pib() does an unserialized read-swap-free of phy->pib:

	pib_old = rtnl_dereference(phy->pib);
	...
	rcu_assign_pointer(phy->pib, pib);
	kfree_rcu(pib_old, rcu);

It assumes the RTNL is held, but ->set_channel is not always called under it: the mac802154 scan worker changes channels via drv_set_channel() without the RTNL. Such an update can race an RTNL-held one on the same phy; both read the same pib_old and both kfree_rcu() it, double-freeing the object. With SLUB percpu sheaves batching kfree_rcu(), this surfaces as a KASAN invalid-free in rcu_free_sheaf().

struct hwsim_phy has no lock for pib. Add one and make the swap atomic with rcu_replace_pointer() under it, dropping the misleading rtnl_dereference().

---
 drivers/net/ieee802154/mac802154_hwsim.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

index 344f63bc94a21..e6a68d522baec 100644
@@ -69,6 +69,8 @@ struct hwsim_phy {
 	struct ieee802154_hw *hw;
 	u32 idx;
 
+	/* Serializes phy->pib_updates. */
+	spinlock_t pib_lock;
 	struct hwsim_pib __rcu *pib;
 
 	bool suspended;

@@ -100,8 +102,10 @@ static int hwsim_hw_channel(struct ieee802154_hw *hw, u8 page, u8 channel)
 	pib->page = page;
 	pib->channel = channel;
 
-	pib_old = rtnl_dereference(phy->pib);
-	rcu_assign_pointer(phy->pib, pib);
+	spin_lock_bh(&phy->pib_lock);
+	pib_old = rcu_replace_pointer(phy->pib, pib,
+				      lockdep_is_held(&phy->pib_lock));
+	spin_unlock_bh(&phy->pib_lock);
 	kfree_rcu(pib_old, rcu);
 	return 0;
 }

@@ -788,6 +792,7 @@ static int hwsim_add_one(struct genl_info *info, struct device *dev,
 		goto err_pib;
 	}
 
+	spin_lock_init(&phy->pib_lock);
 	pib->channel = 13;
 	rcu_assign_pointer(phy->pib, pib);
 	phy->idx = idx;

2.53.0