From 0fa7fa98dbcc2789409ed24e885485e645803d7f Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Tue, 21 Aug 2012 01:06:47 +0000 Subject: packet: Protect packet sk list with mutex (v2) Change since v1: * Fixed inuse counters access spotted by Eric In patch eea68e2f (packet: Report socket mclist info via diag module) I've introduced a "scheduling in atomic" problem in packet diag module -- the socket list is traversed under rcu_read_lock() while performed under it sk mclist access requires rtnl lock (i.e. -- mutex) to be taken. [152363.820563] BUG: scheduling while atomic: crtools/12517/0x10000002 [152363.820573] 4 locks held by crtools/12517: [152363.820581] #0: (sock_diag_mutex){+.+.+.}, at: [] sock_diag_rcv+0x1f/0x3e [152363.820613] #1: (sock_diag_table_mutex){+.+.+.}, at: [] sock_diag_rcv_msg+0xdb/0x11a [152363.820644] #2: (nlk->cb_mutex){+.+.+.}, at: [] netlink_dump+0x23/0x1ab [152363.820693] #3: (rcu_read_lock){.+.+..}, at: [] packet_diag_dump+0x0/0x1af Similar thing was then re-introduced by further packet diag patches (fanount mutex and pgvec mutex for rings) :( Apart from being terribly sorry for the above, I propose to change the packet sk list protection from spinlock to mutex. This lock currently protects two modifications: * sklist * prot inuse counters The sklist modifications can be just reprotected with mutex since they already occur in a sleeping context. The inuse counters modifications are trickier -- the __this_cpu_-s are used inside, thus requiring the caller to handle the potential issues with contexts himself. Since packet sockets' counters are modified in two places only (packet_create and packet_release) we only need to protect the context from being preempted. BH disabling is not required in this case. Signed-off-by: Pavel Emelyanov Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/netns/packet.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/net/netns') diff --git a/include/net/netns/packet.h b/include/net/netns/packet.h index cb4e894c0f8d..4780b080a436 100644 --- a/include/net/netns/packet.h +++ b/include/net/netns/packet.h @@ -8,7 +8,7 @@ #include struct netns_packet { - spinlock_t sklist_lock; + struct mutex sklist_lock; struct hlist_head sklist; }; -- cgit v1.2.3