ChangeSet 1.2325, 2005/03/31 20:36:08-08:00, [EMAIL PROTECTED]
[PKT_SCHED]: Fix deadlock in sch_api.c
While qdisc_create() is holding the rtnl_sem, it may try
to load modules which in turn may try to register devices
(teql is one such case), and it will then hang trying to
retake the rtnl_sem.
Signed-off-by: Catalin(ux aka Dino) BOIE <[EMAIL PROTECTED]>
Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
sch_api.c | 41 ++++++++++++++++++++++++++++++++++-------
1 files changed, 34 insertions(+), 7 deletions(-)
diff -Nru a/net/sched/sch_api.c b/net/sched/sch_api.c
--- a/net/sched/sch_api.c 2005-04-01 09:09:15 -08:00
+++ b/net/sched/sch_api.c 2005-04-01 09:09:15 -08:00
@@ -406,11 +406,29 @@
ops = qdisc_lookup_ops(kind);
#ifdef CONFIG_KMOD
- if (ops==NULL && tca[TCA_KIND-1] != NULL) {
+ if (ops == NULL && kind != NULL) {
char name[IFNAMSIZ];
if (rtattr_strlcpy(name, kind, IFNAMSIZ) < IFNAMSIZ) {
+ /* We dropped the RTNL semaphore in order to
+ * perform the module load. So, even if we
+ * succeeded in loading the module we have to
+ * tell the caller to replay the request. We
+ * indicate this using -EAGAIN.
+ * We replay the request because the device may
+ * go away in the mean time.
+ */
+ rtnl_unlock();
request_module("sch_%s", name);
+ rtnl_lock();
ops = qdisc_lookup_ops(kind);
+ if (ops != NULL) {
+ /* We will try again qdisc_lookup_ops,
+ * so don't keep a reference.
+ */
+ module_put(ops->owner);
+ err = -EAGAIN;
+ goto err_out;
+ }
}
}
#endif
@@ -606,14 +624,20 @@
static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
{
- struct tcmsg *tcm = NLMSG_DATA(n);
- struct rtattr **tca = arg;
+ struct tcmsg *tcm;
+ struct rtattr **tca;
struct net_device *dev;
- u32 clid = tcm->tcm_parent;
- struct Qdisc *q = NULL;
- struct Qdisc *p = NULL;
+ u32 clid;
+ struct Qdisc *q, *p;
int err;
+replay:
+ /* Reinit, just in case something touches this. */
+ tcm = NLMSG_DATA(n);
+ tca = arg;
+ clid = tcm->tcm_parent;
+ q = p = NULL;
+
if ((dev = __dev_get_by_index(tcm->tcm_ifindex)) == NULL)
return -ENODEV;
@@ -707,8 +731,11 @@
q = qdisc_create(dev, tcm->tcm_parent, tca, &err);
else
q = qdisc_create(dev, tcm->tcm_handle, tca, &err);
- if (q == NULL)
+ if (q == NULL) {
+ if (err == -EAGAIN)
+ goto replay;
return err;
+ }
graft:
if (1) {
-
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