ieee802154: hwsim: serialize pib updates to fix double-free

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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: f25da51fdc ("ieee802154: hwsim: add replacement for fakelb")
Signed-off-by: David Carlier <devnexen@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/20260709221858.158063-1-devnexen@gmail.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

...

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David Carlier 2026-07-09 23:18:58 +01:00 • committed by Stefan Schmidt

parent bf79662bc8

commit 979d5b8de8

1 changed files with 7 additions and 3 deletions

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drivers/net/ieee802154/mac802154_hwsim.c

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