From f2f17ef7c7a9ac2a9ed1160c768c67d2cf86b8d5 Mon Sep 17 00:00:00 2001 From: Jiri Pirko Date: Thu, 9 May 2013 04:23:40 +0000 Subject: macvlan: fix passthru mode race between dev removal and rx path [ Upstream commit 233c7df0821c4190e2d3f4be0f2ca0ab40a5ed8c, note that I had to add list_first_or_null_rcu to rculist.h in order to accomodate this fix. ] Currently, if macvlan in passthru mode is created and data are rxed and you remove this device, following panic happens: NULL pointer dereference at 0000000000000198 IP: [] macvlan_handle_frame+0x153/0x1f7 [macvlan] I'm using following script to trigger this: I run this script while "ping -f" is running on another machine to send packets to e1 rx. Reason of the panic is that list_first_entry() is blindly called in macvlan_handle_frame() even if the list was empty. vlan is set to incorrect pointer which leads to the crash. I'm fixing this by protecting port->vlans list by rcu and by preventing from getting incorrect pointer in case the list is empty. Introduced by: commit eb06acdc85585f2 "macvlan: Introduce 'passthru' mode to takeover the underlying device" Signed-off-by: Jiri Pirko Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/linux/rculist.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'include') diff --git a/include/linux/rculist.h b/include/linux/rculist.h index d079290843a..6f95e241ed6 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -241,6 +241,23 @@ static inline void list_splice_init_rcu(struct list_head *list, #define list_first_entry_rcu(ptr, type, member) \ list_entry_rcu((ptr)->next, type, member) +/** + * list_first_or_null_rcu - get the first element from a list + * @ptr: the list head to take the element from. + * @type: the type of the struct this is embedded in. + * @member: the name of the list_struct within the struct. + * + * Note that if the list is empty, it returns NULL. + * + * This primitive may safely run concurrently with the _rcu list-mutation + * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). + */ +#define list_first_or_null_rcu(ptr, type, member) \ + ({struct list_head *__ptr = (ptr); \ + struct list_head __rcu *__next = list_next_rcu(__ptr); \ + likely(__ptr != __next) ? container_of(__next, type, member) : NULL; \ + }) + /** * list_for_each_entry_rcu - iterate over rcu list of given type * @pos: the type * to use as a loop cursor. -- cgit v1.2.3