[PATCH] ieee802154: hwsim: serialize pib updates to fix double-free
From: David Carlier <hidden>
Date: 2026-07-09 22:19:04
Also in:
lkml, stable
Subsystem:
ieee 802.15.4 subsystem, networking drivers, the rest · Maintainers:
Alexander Aring, Stefan Schmidt, Miquel Raynal, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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(). Reported-by: syzbot+60332fd095f8bb2946ad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=60332fd095f8bb2946ad Fixes: f25da51fdc38 ("ieee802154: hwsim: add replacement for fakelb") Signed-off-by: David Carlier <redacted> Cc: <redacted> --- drivers/net/ieee802154/mac802154_hwsim.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ieee802154/mac802154_hwsim.c b/drivers/net/ieee802154/mac802154_hwsim.c
index 6daa0f198b9f..a9bd1555d2dc 100644
--- a/drivers/net/ieee802154/mac802154_hwsim.c
+++ b/drivers/net/ieee802154/mac802154_hwsim.c@@ -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);
--
2.53.0