Revision 99f62a746066fa436aa15d4606a538569540db08 authored by Vladimir Oltean on 21 September 2020, 22:07:09 UTC, committed by David S. Miller on 22 September 2020, 00:37:44 UTC
When calling the RCU brother of br_vlan_get_pvid(), lockdep warns: ============================= WARNING: suspicious RCU usage 5.9.0-rc3-01631-g13c17acb8e38-dirty #814 Not tainted ----------------------------- net/bridge/br_private.h:1054 suspicious rcu_dereference_protected() usage! Call trace: lockdep_rcu_suspicious+0xd4/0xf8 __br_vlan_get_pvid+0xc0/0x100 br_vlan_get_pvid_rcu+0x78/0x108 The warning is because br_vlan_get_pvid_rcu() calls nbp_vlan_group() which calls rtnl_dereference() instead of rcu_dereference(). In turn, rtnl_dereference() calls rcu_dereference_protected() which assumes operation under an RCU write-side critical section, which obviously is not the case here. So, when the incorrect primitive is used to access the RCU-protected VLAN group pointer, READ_ONCE() is not used, which may cause various unexpected problems. I'm sad to say that br_vlan_get_pvid() and br_vlan_get_pvid_rcu() cannot share the same implementation. So fix the bug by splitting the 2 functions, and making br_vlan_get_pvid_rcu() retrieve the VLAN groups under proper locking annotations. Fixes: 7582f5b70f9a ("bridge: add br_vlan_get_pvid_rcu()") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent 47cec3f
locking-selftest-wsem.h
/* SPDX-License-Identifier: GPL-2.0 */
#undef LOCK
#define LOCK WSL
#undef UNLOCK
#define UNLOCK WSU
#undef RLOCK
#define RLOCK RSL
#undef WLOCK
#define WLOCK WSL
#undef INIT
#define INIT RWSI
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