Date: Sat, 5 May 2018 20:51:45 +0200 From: Andrew Lunn <andrew@...n.ch> To: Kees Cook <keescook@...omium.org> Cc: Salvatore Mesoraca <s.mesoraca16@...il.com>, Florian Fainelli <f.fainelli@...il.com>, Vivien Didelot <vivien.didelot@...oirfairelinux.com>, LKML <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Network Development <netdev@...r.kernel.org>, "David S. Miller" <davem@...emloft.net> Subject: Re: [PATCH] net: dsa: drop some VLAs in switch.c > > You could make the bitmap part of the dsa_switch structure. This is > > allocated by dsa_switch_alloc() and is passed the number of ports. > > Doing the allocation there means you don't need to worry about it > > failing in dsa_switch_mdb_add() or dsa_switch_vlan_add(). > > Are dsa_switch_mdb_add() and dsa_switch_vlan_add() guaranteed to be > single-threaded? Yes, that is the interesting question here.... against each other, or themselves? They are called from a notifier chain. It is the same notifier chain for both dsa_switch_mdb_add() and dsa_switch_vlan_add(). notifier_call_chain() itself appears to not provide any guarantees about the same handler being called in parallel. It is dsa_port_notify() which is calling the notifier_call_chain(). This is being called by both dsa_port_vlan_add() and dsa_port_mdb_add() in dsa_slave_port_obj_add(). This is a switchdev op. switchdev_port_obj_add_now() does have ASSERT_RTNL(); So that should serialize everything. Andrew
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