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
gcc-version.sh
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
#
# gcc-version gcc-command
#
# Print the gcc version of `gcc-command' in a 5 or 6-digit form
# such as `29503' for gcc-2.95.3, `30301' for gcc-3.3.1, etc.
compiler="$*"
if [ ${#compiler} -eq 0 ]; then
echo "Error: No compiler specified." >&2
printf "Usage:\n\t$0 <gcc-command>\n" >&2
exit 1
fi
MAJOR=$(echo __GNUC__ | $compiler -E -x c - | tail -n 1)
MINOR=$(echo __GNUC_MINOR__ | $compiler -E -x c - | tail -n 1)
PATCHLEVEL=$(echo __GNUC_PATCHLEVEL__ | $compiler -E -x c - | tail -n 1)
printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL
Computing file changes ...
