[ovs-dev] [PATCH] datapath-windows: Fix bugs in cleaner threads

Anand Kumar kumaranand at vmware.com
Fri Sep 22 21:39:11 UTC 2017


Good catch. Thanks for fixing it.

Acked-by: Anand Kumar <kumaranand at vmware.com> 

Thanks,
Anand Kumar

On 9/22/17, 2:24 PM, "ovs-dev-bounces at openvswitch.org on behalf of Shashank Ram" <ovs-dev-bounces at openvswitch.org on behalf of rams at vmware.com> wrote:

    Conntrack, Conntrack-related, Stt, and IP fragmentation
    have cleaner threads that run periodically to clean
    up their respective tables. During driver unload,
    OvsExtDetach() calls into routines that are meant
    for explicitly cleaning these tables up and freeing
    the resources associated with these threads.
    
    If during driver unload, these cleaner threads run
    immediately after the resources are freed, such as locks
    used by these threads, then the cleaner threads result
    in a kernel crash since they try to acquire locks
    that have already been freed.
    
    For eg, OvsIpFragmentEntryCleaner() caused a kernel
    crash because it tried to acquire a lock that was
    already freed by OvsCleanupIpFragment().
    
    The fix is to simply exit the cleaner thread if the
    lock associated with the thread is not initialized,
    because the only way the threads can run when the lock
    is invalid is when the lock has been freed up during
    driver unload.
    
    Testint done:
    Verified that cleaner threads run as expected without
    crashing during driver unload.
    
    Signed-off-by: Shashank Ram <rams at vmware.com>
    ---
     datapath-windows/ovsext/Conntrack-related.c | 6 +++++-
     datapath-windows/ovsext/Conntrack.c         | 6 +++++-
     datapath-windows/ovsext/IpFragment.c        | 6 +++++-
     datapath-windows/ovsext/Stt.c               | 4 ++++
     4 files changed, 19 insertions(+), 3 deletions(-)
    
    diff --git a/datapath-windows/ovsext/Conntrack-related.c b/datapath-windows/ovsext/Conntrack-related.c
    index 16ed6f7..ec4b536 100644
    --- a/datapath-windows/ovsext/Conntrack-related.c
    +++ b/datapath-windows/ovsext/Conntrack-related.c
    @@ -181,10 +181,14 @@ OvsCtRelatedEntryCleaner(PVOID data)
         POVS_CT_THREAD_CTX context = (POVS_CT_THREAD_CTX)data;
         PLIST_ENTRY link, next;
         POVS_CT_REL_ENTRY entry;
    +    LOCK_STATE_EX lockState;
         BOOLEAN success = TRUE;
    
         while (success) {
    -        LOCK_STATE_EX lockState;
    +        if (ovsCtRelatedLockObj == NULL) {
    +            /* Lock has been freed by 'OvsCleanupCtRelated()' */
    +            break;
    +        }
             NdisAcquireRWLockWrite(ovsCtRelatedLockObj, &lockState, 0);
             if (context->exit) {
                 NdisReleaseRWLock(ovsCtRelatedLockObj, &lockState);
    diff --git a/datapath-windows/ovsext/Conntrack.c b/datapath-windows/ovsext/Conntrack.c
    index f0d135b..3203411 100644
    --- a/datapath-windows/ovsext/Conntrack.c
    +++ b/datapath-windows/ovsext/Conntrack.c
    @@ -980,10 +980,14 @@ OvsConntrackEntryCleaner(PVOID data)
         POVS_CT_THREAD_CTX context = (POVS_CT_THREAD_CTX)data;
         PLIST_ENTRY link, next;
         POVS_CT_ENTRY entry;
    +    LOCK_STATE_EX lockState;
         BOOLEAN success = TRUE;
    
         while (success) {
    -        LOCK_STATE_EX lockState;
    +        if (ovsConntrackLockObj == NULL) {
    +            /* Lock has been freed by 'OvsCleanupConntrack()' */
    +            break;
    +        }
             NdisAcquireRWLockWrite(ovsConntrackLockObj, &lockState, 0);
             if (context->exit) {
                 NdisReleaseRWLock(ovsConntrackLockObj, &lockState);
    diff --git a/datapath-windows/ovsext/IpFragment.c b/datapath-windows/ovsext/IpFragment.c
    index fee361a..ad48834 100644
    --- a/datapath-windows/ovsext/IpFragment.c
    +++ b/datapath-windows/ovsext/IpFragment.c
    @@ -444,10 +444,14 @@ OvsIpFragmentEntryCleaner(PVOID data)
         POVS_IPFRAG_THREAD_CTX context = (POVS_IPFRAG_THREAD_CTX)data;
         PLIST_ENTRY link, next;
         POVS_IPFRAG_ENTRY entry;
    +    LOCK_STATE_EX lockState;
         BOOLEAN success = TRUE;
    
         while (success) {
    -        LOCK_STATE_EX lockState;
    +        if (ovsIpFragmentHashLockObj == NULL) {
    +            /* Lock has been freed by 'OvsCleanupIpFragment()' */
    +            break;
    +        }
             NdisAcquireRWLockWrite(ovsIpFragmentHashLockObj, &lockState, 0);
             if (context->exit) {
                 NdisReleaseRWLock(ovsIpFragmentHashLockObj, &lockState);
    diff --git a/datapath-windows/ovsext/Stt.c b/datapath-windows/ovsext/Stt.c
    index b6236fd..f98070f 100644
    --- a/datapath-windows/ovsext/Stt.c
    +++ b/datapath-windows/ovsext/Stt.c
    @@ -551,6 +551,10 @@ OvsSttDefragCleaner(PVOID data)
         BOOLEAN success = TRUE;
    
         while (success) {
    +        if (&OvsSttSpinLock == NULL) {
    +            /* Lock has been freed by 'OvsCleanupSttDefragmentation()' */
    +            break;
    +        }
             NdisAcquireSpinLock(&OvsSttSpinLock);
             if (context->exit) {
                 NdisReleaseSpinLock(&OvsSttSpinLock);
    --
    2.9.3.windows.2
    
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