[RHEL7,COMMIT] venetdev: fix race between veip shutdown and add veip entry

Submitted by Konstantin Khorenko on Dec. 28, 2018, 2:49 p.m.


Message ID 201812281449.wBSEnSbh023897@finist-ce7.sw.ru
State New
Series "Series without cover letter"
Headers show

Commit Message

Konstantin Khorenko Dec. 28, 2018, 2:49 p.m.
The commit is pushed to "branch-rh7-3.10.0-957.1.3.vz7.83.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.1.3.vz7.83.4
commit 696f833c575ba3a176eecdbe3ad607256ea36397
Author: Konstantin Khorenko <khorenko@virtuozzo.com>
Date:   Thu Dec 27 12:17:29 2018 +0300

    venetdev: fix race between veip shutdown and add veip entry
    If veip entry is added via cgroup ve::ip_allow interface
    after veip_shutdown() is called, veip structure leaks.
    Moreover, you won't be able to assign same IP address to
    a Container (same after restart or another one) because
    veip entry exists, but veip->veid mismatches.
    This happens because veip_entry_add() creates new veip struct
    if ve->veip == NULL. The intention was to handle the case when
    we load vznetdev module after a Container start.
    In fact this code does not work now: venet device is create by
    venet_newlink() which does it only in case env->veip == NULL,
    so venet device will be never created in this case.
    Let's make veip_entry_add() to fail in case ve->veip == NULL
    Let's also add a warning on veip struct leak. Just in case.
    Note: we come veip_put() from two paths:
    1) __veip_stop()->veip_release(), where ip_lh is definitely empty,
    2) venet_exit()->veip_cleanup(), which is called on module unload,
       on module unload. Module may be unloaded only after all veip were
       destroyed, i.e., went thru (1) path.
    Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
    Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
 drivers/net/venetdev.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

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diff --git a/drivers/net/venetdev.c b/drivers/net/venetdev.c
index 429a74c77a4b..fb02660035b3 100644
--- a/drivers/net/venetdev.c
+++ b/drivers/net/venetdev.c
@@ -87,8 +87,10 @@  static void veip_free(struct rcu_head *rcu)
 int veip_put(struct veip_struct *veip)
-	if (!list_empty(&veip->ip_lh))
+	if (!list_empty(&veip->ip_lh)) {
+		WARN_ONCE(1, "Leaking veip structure 0x%p", veip);
 		return 0;
+	}
 	call_rcu(&veip->rcu, veip_free);
@@ -283,14 +285,12 @@  static int veip_entry_add(struct ve_struct *ve, struct ve_addr_struct *addr)
 	if (entry == NULL)
 		return -ENOMEM;
+	spin_lock(&veip_lock);
 	if (ve->veip == NULL) {
-		/* This can happen if we load venet AFTER ve was started */
-	       	err = veip_start(ve);
-		if (err < 0)
-			goto out;
+		err = -ENODEV;
+		goto out_unlock;
-	spin_lock(&veip_lock);
 	found = venet_entry_lookup(addr);
 	if (found != NULL) {
 		err = veip_entry_conflict(found, ve);
@@ -303,9 +303,9 @@  static int veip_entry_add(struct ve_struct *ve, struct ve_addr_struct *addr)
 	err = 0;
 	entry = NULL;
 	if (entry != NULL)