mm: slub: call WARN() when detecting a slab corruption

If a slab object is corrupted or an error occurs in its internal
validation, continuing after restoration may cause other side effects.
At this point, it is difficult to debug because the problem occurred in
the past. It is useful to use WARN() to catch errors at the point of
issue because WARN() could trigger panic for system debugging when
panic_on_warn is enabled. WARN() is added where to detect the error on
slab_err and object_err.

It makes sense to only do the WARN() after printing the logs. slab_err
is splited to __slab_err that calls the WARN() and it is called after
printing logs.

Signed-off-by: Hyesoo Yu <hyesoo.yu@samsung.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: Hyesoo Yu

mm/slub.c

@@ -1026,7 +1026,7 @@ static void slab_bug(struct kmem_cache *s, char *fmt, ...)
 	vaf.fmt = fmt;
 	vaf.va = &args;
 	pr_err("=============================================================================\n");
-	pr_err("BUG %s (%s): %pV\n", s->name, print_tainted(), &vaf);
+	pr_err("BUG %s (%s): %pV\n", s ? s->name : "<unknown>", print_tainted(), &vaf);
 	pr_err("-----------------------------------------------------------------------------\n\n");
 	va_end(args);
 }
@@ -1085,8 +1085,6 @@ static void print_trailer(struct kmem_cache *s, struct slab *slab, u8 *p)
 		/* Beginning of the filler is the free pointer */
 		print_section(KERN_ERR, "Padding  ", p + off,
 			      size_from_object(s) - off);
-
-	dump_stack();
 }
 
 static void object_err(struct kmem_cache *s, struct slab *slab,
@@ -1098,6 +1096,8 @@ static void object_err(struct kmem_cache *s, struct slab *slab,
 	slab_bug(s, "%s", reason);
 	print_trailer(s, slab, object);
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
+
+	WARN_ON(1);
 }
 
 static bool freelist_corrupted(struct kmem_cache *s, struct slab *slab,
@@ -1114,6 +1114,17 @@ static bool freelist_corrupted(struct kmem_cache *s, struct slab *slab,
 	return false;
 }
 
+static void __slab_err(struct slab *slab)
+{
+	if (slab_in_kunit_test())
+		return;
+
+	print_slab_info(slab);
+	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
+
+	WARN_ON(1);
+}
+
 static __printf(3, 4) void slab_err(struct kmem_cache *s, struct slab *slab,
 			const char *fmt, ...)
 {
@@ -1127,9 +1138,7 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct slab *slab,
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);
 	slab_bug(s, "%s", buf);
-	print_slab_info(slab);
-	dump_stack();
-	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
+	__slab_err(slab);
 }
 
 static void init_object(struct kmem_cache *s, void *object, u8 val)
@@ -1302,9 +1311,10 @@ slab_pad_check(struct kmem_cache *s, struct slab *slab)
 	while (end > fault && end[-1] == POISON_INUSE)
 		end--;
 
-	slab_err(s, slab, "Padding overwritten. 0x%p-0x%p @offset=%tu",
-			fault, end - 1, fault - start);
+	slab_bug(s, "Padding overwritten. 0x%p-0x%p @offset=%tu",
+		 fault, end - 1, fault - start);
 	print_section(KERN_ERR, "Padding ", pad, remainder);
+	__slab_err(slab);
 
 	restore_bytes(s, "slab padding", POISON_INUSE, fault, end);
 }
@@ -1620,12 +1630,12 @@ static inline int free_consistency_checks(struct kmem_cache *s,
 			slab_err(s, slab, "Attempt to free object(0x%p) outside of slab",
 				 object);
 		} else if (!slab->slab_cache) {
-			pr_err("SLUB <none>: no slab for object 0x%p.\n",
-			       object);
-			dump_stack();
-		} else
+			slab_err(NULL, slab, "No slab cache for object 0x%p",
+				 object);
+		} else {
 			object_err(s, slab, object,
-					"page slab pointer corrupt.");
+				   "page slab pointer corrupt.");
+		}
 		return 0;
 	}
 	return 1;
@@ -5728,14 +5738,14 @@ static int calculate_sizes(struct kmem_cache_args *args, struct kmem_cache *s)
 	return !!oo_objects(s->oo);
 }
 
-static void list_slab_objects(struct kmem_cache *s, struct slab *slab,
-			      const char *text)
+static void list_slab_objects(struct kmem_cache *s, struct slab *slab)
 {
 #ifdef CONFIG_SLUB_DEBUG
 	void *addr = slab_address(slab);
 	void *p;
 
-	slab_err(s, slab, text, s->name);
+	if (!slab_add_kunit_errors())
+		slab_bug(s, "Objects remaining on __kmem_cache_shutdown()");
 
 	spin_lock(&object_map_lock);
 	__fill_map(object_map, s, slab);
@@ -5750,6 +5760,8 @@ static void list_slab_objects(struct kmem_cache *s, struct slab *slab,
 		}
 	}
 	spin_unlock(&object_map_lock);
+
+	__slab_err(slab);
 #endif
 }
 
@@ -5770,8 +5782,7 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
 			remove_partial(n, slab);
 			list_add(&slab->slab_list, &discard);
 		} else {
-			list_slab_objects(s, slab,
-			  "Objects remaining in %s on __kmem_cache_shutdown()");
+			list_slab_objects(s, slab);
 		}
 	}
 	spin_unlock_irq(&n->list_lock);