[dpdk-dev] Bug with commit 64051bb1 (devargs: unify scratch buffer storage)

["Harris, James R" <james.r.harris@intel.com>]

Hi,

SPDK has identified a regression with commit 64051bb1 (devargs: unify scratch buffer storage).  The issue seems to be with this part of the patch:

@@ -276,15 +287,8 @@ rte_devargs_insert(struct rte_devargs **da)
                if (strcmp(listed_da->bus->name, (*da)->bus->name) == 0 &&
                                strcmp(listed_da->name, (*da)->name) == 0) {
                        /* device already in devargs list, must be updated */
-                       listed_da->type = (*da)->type;
-                       listed_da->policy = (*da)->policy;
-                       free(listed_da->args);
-                       listed_da->args = (*da)->args;
-                       listed_da->bus = (*da)->bus;
-                       listed_da->cls = (*da)->cls;
-                       listed_da->bus_str = (*da)->bus_str;
-                       listed_da->cls_str = (*da)->cls_str;
-                       listed_da->data = (*da)->data;
+                       rte_devargs_reset(listed_da);
+                       *listed_da = **da;
                        /* replace provided devargs with found one */
                        free(*da);
                        *da = listed_da;


Previously the data members were copied one-by-one, preserving the pointers in the listed_da’s TAILQ_ENTRY.  But after this patch, rte_devargs_reset() zeroes the entire rte_devargs structure, including the pointers in the TAILQ_ENTRY.  If we do a subsequent rte_devargs_remove() on this same entry, we segfault since the TAILQ_ENTRY’s pointers are invalid.  There could be similar segfaults with any subsequent rte_devargs_insert() calls that require iterating the global list of devargs entries.

rte_devargs_insert() could manually copy the TAILQ_ENTRY pointers to *da before calling rte_devargs_reset() – that at least fixes the SPDK regression.  But it’s not clear to me how many of the other rte_devargs_reset() callsites added by this patch also need to be changed in some way.

Thanks,

-Jim