FreeResource() keeps clientTable[cid].elements up to date with the number of resources allocated to the client. The other free resource functions (FreeResourceByType(), FreeClientNeverRetainResources() and FreeClientResources()) don't maintain this invariant.
Typically, the only consequence is that the element count is too high and we end up allocating the hash table bigger than necessary. However, FreeResource() also relies on the element count to restart the search if the list of resources has been changed during a resource destruction callback. Since FreeResourceByType() doesn't update the count, if we call that from a resource destruction callback from FreeResource(), the loop isn't restarted and we end up following an invalid next pointer. Furthermore, LookupClientResourceComplex() and FreeClientNeverRetainResources() don't use the element count to detect if a callback deleted a resource and may end up following an invalid next pointer if the resource system is called into recursively. Signed-off-by: Kristian Høgsberg <k...@bitplanet.net> --- dix/resource.c | 17 +++++++++++++++-- 1 files changed, 15 insertions(+), 2 deletions(-) diff --git a/dix/resource.c b/dix/resource.c index 91d0cfb..048fad1 100644 --- a/dix/resource.c +++ b/dix/resource.c @@ -589,6 +589,7 @@ FreeResourceByType(XID id, RESTYPE type, Bool skipFree) res->value, TypeNameString(res->type)); #endif *prev = res->next; + clientTable[cid].elements--; CallResourceStateCallback(ResourceStateFreeing, res); @@ -707,20 +708,25 @@ LookupClientResourceComplex( ResourcePtr *resources; ResourcePtr this, next; pointer value; - int i; + int i, elements; + int *eltptr; if (!client) client = serverClient; resources = clientTable[client->index].resources; + eltptr = &clientTable[client->index].elements; for (i = 0; i < clientTable[client->index].buckets; i++) { for (this = resources[i]; this; this = next) { next = this->next; if (!type || this->type == type) { /* workaround func freeing the type as DRI1 does */ value = this->value; + elements = *eltptr; if((*func)(value, this->id, cdata)) return value; + if (*eltptr != elements) + next = resources[i]; /* start over */ } } } @@ -734,12 +740,14 @@ FreeClientNeverRetainResources(ClientPtr client) ResourcePtr *resources; ResourcePtr this; ResourcePtr *prev; - int j; + int j, elements; + int *eltptr; if (!client) return; resources = clientTable[client->index].resources; + eltptr = &clientTable[client->index].elements; for (j=0; j < clientTable[client->index].buckets; j++) { prev = &resources[j]; @@ -753,11 +761,15 @@ FreeClientNeverRetainResources(ClientPtr client) this->value, TypeNameString(this->type)); #endif *prev = this->next; + clientTable[client->index].elements--; CallResourceStateCallback(ResourceStateFreeing, this); + elements = *eltptr; (*DeleteFuncs[rtype & TypeMask])(this->value, this->id); xfree(this); + if (*eltptr != elements) + prev = &resources[j]; /* prev may no longer be valid */ } else prev = &this->next; @@ -804,6 +816,7 @@ FreeClientResources(ClientPtr client) this->value, TypeNameString(this->type)); #endif *head = this->next; + clientTable[client->index].elements--; CallResourceStateCallback(ResourceStateFreeing, this); -- 1.7.0.1 _______________________________________________ xorg-devel@lists.x.org: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel