Fix for the "kmem [-s|-S] <address>" command, and the "rd -S[S]"

and "bt -F[F]" options.  Without the patch, if the page structure
associated with a memory address still contains a (stale) pointer to
the address of a kmem_cache structure, but whose page.flags does not
have the PG_slab bit set, the address is incorrectly presumed to be
contained within that slab cache.  As as result, the "kmem" command
may display one or more messages indicating a "bad inuse counter", a
"bad next pointer" or a "bad s_mem pointer", followed by an "address
not found in cache" error message.  The "rd -S[S]" and "bt -F[F]"
commands may mislabel memory locations as belonging to slab caches.
(anderson@redhat.com)

memory.c

@@ -8700,8 +8700,7 @@ static char *
 vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose)
 {
 	physaddr_t paddr;
-	ulong page;
-	ulong cache;
+	ulong page, cache, page_flags;
 
         if (!kvtop(NULL, vaddr, &paddr, 0)) {
 		if (verbose)
@@ -8719,6 +8718,14 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose)
 		return NULL;
 	}
 
+	if (vt->PG_slab) {
+		readmem(page+OFFSET(page_flags), KVADDR,
+			&page_flags, sizeof(ulong), "page.flags",
+			FAULT_ON_ERROR);
+		if (!(page_flags & (1 << vt->PG_slab)))
+			return NULL;
+	}
+
 	if ((vt->flags & KMALLOC_SLUB) ||
 	    ((vt->flags & KMALLOC_COMMON) && 
 	     VALID_MEMBER(page_slab) && VALID_MEMBER(page_first_page))) {