[libvirt] [PATCH] virnwfilterbindingobj: Introduce and use virNWFilterBindingObjStealDef

https://bugzilla.redhat.com/show_bug.cgi?id=1686927 When trying to create a nwfilter binding via nwfilterBindingCreateXML() we may encounter a crash. The sequence of functions called is as follows: 1) nwfilterBindingCreateXML() parses the XML and calls virNWFilterBindingObjListAdd() which calls virNWFilterBindingObjListAddLocked() 2) Here, @binding is not found because binding->remove is set. 3) Therefore, controls continue with creating new @binding, setting its def to the one from 1) and adding it to the hash table. 4) This fails, because the binding is still in the hash table (duplicate key is detected). 5) The control jumps to 'error' label where virNWFilterBindingObjEndAPI() is called which frees the binding definition passed. 6) Error is propagated to the caller, which calls virNWFilterBindingDefFree() over the definition again. The solution is to unset binding->def in case of failure so it's not freed in step 5). Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- Technically, this is a v2 of: https://www.redhat.com/archives/libvir-list/2019-March/msg01209.html But since this one implements different approach than v1 I'm not marking it as such. src/conf/virnwfilterbindingobj.c | 10 ++++++++++ src/conf/virnwfilterbindingobj.h | 3 +++ src/conf/virnwfilterbindingobjlist.c | 4 ++++ src/libvirt_private.syms | 1 + 4 files changed, 18 insertions(+) diff --git a/src/conf/virnwfilterbindingobj.c b/src/conf/virnwfilterbindingobj.c index 23978d4207..68afb9c434 100644 --- a/src/conf/virnwfilterbindingobj.c +++ b/src/conf/virnwfilterbindingobj.c @@ -88,6 +88,16 @@ virNWFilterBindingObjSetDef(virNWFilterBindingObjPtr obj, } +virNWFilterBindingDefPtr +virNWFilterBindingObjStealDef(virNWFilterBindingObjPtr obj) +{ + virNWFilterBindingDefPtr def; + + VIR_STEAL_PTR(def, obj->def); + return def; +} + + bool virNWFilterBindingObjGetRemoving(virNWFilterBindingObjPtr obj) { diff --git a/src/conf/virnwfilterbindingobj.h b/src/conf/virnwfilterbindingobj.h index 8e5fbee35f..b26bb3c8ec 100644 --- a/src/conf/virnwfilterbindingobj.h +++ b/src/conf/virnwfilterbindingobj.h @@ -39,6 +39,9 @@ void virNWFilterBindingObjSetDef(virNWFilterBindingObjPtr obj, virNWFilterBindingDefPtr def); +virNWFilterBindingDefPtr +virNWFilterBindingObjStealDef(virNWFilterBindingObjPtr obj); + bool virNWFilterBindingObjGetRemoving(virNWFilterBindingObjPtr obj); diff --git a/src/conf/virnwfilterbindingobjlist.c b/src/conf/virnwfilterbindingobjlist.c index 06ccbf53af..4ee2c1b194 100644 --- a/src/conf/virnwfilterbindingobjlist.c +++ b/src/conf/virnwfilterbindingobjlist.c @@ -167,6 +167,7 @@ virNWFilterBindingObjListAddLocked(virNWFilterBindingObjListPtr bindings, virNWFilterBindingDefPtr def) { virNWFilterBindingObjPtr binding; + bool stealDef = false; /* See if a binding with matching portdev already exists */ if ((binding = virNWFilterBindingObjListFindByPortDevLocked( @@ -181,6 +182,7 @@ virNWFilterBindingObjListAddLocked(virNWFilterBindingObjListPtr bindings, goto error; virNWFilterBindingObjSetDef(binding, def); + stealDef = true; if (virNWFilterBindingObjListAddObjLocked(bindings, binding) < 0) goto error; @@ -188,6 +190,8 @@ virNWFilterBindingObjListAddLocked(virNWFilterBindingObjListPtr bindings, return binding; error: + if (stealDef) + virNWFilterBindingObjStealDef(binding); virNWFilterBindingObjEndAPI(&binding); return NULL; } diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index 26f10bd47f..a33f9e61b1 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -1101,6 +1101,7 @@ virNWFilterBindingObjParseFile; virNWFilterBindingObjSave; virNWFilterBindingObjSetDef; virNWFilterBindingObjSetRemoving; +virNWFilterBindingObjStealDef; # conf/virnwfilterbindingobjlist.h -- 2.19.2