mm/slub: clean up create_unique_id()

As Christophe JAILLET suggested [1]

In create_unique_id(),

"looks that ID_STR_LENGTH could even be reduced to 32 or 16.

The 2nd BUG_ON at the end of the function could certainly be just
removed as well or remplaced by a:
        if (p > name + ID_STR_LENGTH - 1) {
                kfree(name);
                return -E<something>;
        }
"

According to above suggestion, let's do below cleanups:
1. reduce ID_STR_LENGTH to 32, as the buffer size should be enough;
2. use WARN_ON instead of BUG_ON() and return error if check condition
is true;
3. use snprintf instead of sprintf to avoid overflow.

[1] https://lore.kernel.org/linux-mm/2025305d-16db-abdf-6cd3-1fb93371c2b4@wanadoo.fr/

Suggested-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Chao Yu <chao.yu@oppo.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/mm/slub.c b/mm/slub.c
index dc59b9e8c66f6007ab84e0460aad087358fe2fd8..8f80d9bc507f1c2339c278c17fad92fed0df238d 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5874,7 +5874,7 @@ static inline struct kset *cache_kset(struct kmem_cache *s)
        return slab_kset;
 }
 
-#define ID_STR_LENGTH 64
+#define ID_STR_LENGTH 32
 
 /* Create a unique string id for a slab cache:
  *
@@ -5907,9 +5907,12 @@ static char *create_unique_id(struct kmem_cache *s)
                *p++ = 'A';
        if (p != name + 1)
                *p++ = '-';
-       p += sprintf(p, "%07u", s->size);
+       p += snprintf(p, ID_STR_LENGTH - (p - name), "%07u", s->size);
 
-       BUG_ON(p > name + ID_STR_LENGTH - 1);
+       if (WARN_ON(p > name + ID_STR_LENGTH - 1)) {
+               kfree(name);
+               return ERR_PTR(-EINVAL);
+       }
        return name;
 }