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caif: Bugfix list_del_rcu race in cfmuxl_ctrlcmd. 

Always use cfmuxl_remove_uplayer when removing a up-layer.
cfmuxl_ctrlcmd() can be called independently and in parallel with
cfmuxl_remove_uplayer(). The race between them could cause list_del_rcu
to be called on a node which has been already taken out from the list.
That lead to a (rare) crash on accessing poisoned node->prev inside
list_del_rcu.

This fix ensures that deletion are done holding the same lock.

Reported-by: Dmitry Tarnyagin <dmitry.tarnyagin@stericsson.com>
Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
sjur.brandeland@stericsson.com 2012-02-02 01:21:02 +00:00 committed by David S. Miller
parent c31c151b1c
commit b01377a420
1 changed files with 2 additions and 8 deletions
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10
net/caif/cfmuxl.c
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@ -248,7 +248,6 @@ static void cfmuxl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
{
struct cfmuxl *muxl = container_obj(layr);
struct cflayer *layer;
int idx;
rcu_read_lock();
list_for_each_entry_rcu(layer, &muxl->srvl_list, node) {
@ -257,14 +256,9 @@ static void cfmuxl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
if ((ctrl == _CAIF_CTRLCMD_PHYIF_DOWN_IND ||
ctrl == CAIF_CTRLCMD_REMOTE_SHUTDOWN_IND) &&
layer->id != 0) {
layer->id != 0)
cfmuxl_remove_uplayer(layr, layer->id);
idx = layer->id % UP_CACHE_SIZE;
spin_lock_bh(&muxl->receive_lock);
RCU_INIT_POINTER(muxl->up_cache[idx], NULL);
list_del_rcu(&layer->node);
spin_unlock_bh(&muxl->receive_lock);
}
/* NOTE: ctrlcmd is not allowed to block */
layer->ctrlcmd(layer, ctrl, phyid);
}