Re: [PATCH] mm/slub: clean up create_unique_id()
From: Chao Yu
Date: Sun Sep 25 2022 - 11:25:26 EST
On 2022/9/23 4:47, Vlastimil Babka wrote:
On 9/18/22 11:21, Chao Yu wrote:
From: Chao Yu <chao.yu@xxxxxxxx>
As Christophe JAILLET suggested:
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. remove BUG_ON() and return error if check condition is true.
I'd leave a WARN_ON there as we really don't expect this to happen, so if it
does, we should be loud about it and not silently fail.
Agreed.
Link: https://lore.kernel.org/linux-mm/2025305d-16db-abdf-6cd3-1fb93371c2b4@xxxxxxxxxx/
Suggested-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Fixes: 81819f0fc828 ("SLUB core")
Signed-off-by: Chao Yu <chao.yu@xxxxxxxx>
---
mm/slub.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 5ba6db62a5ab..a045c1ca8772 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5883,7 +5883,7 @@ 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:
*
@@ -5919,7 +5919,10 @@ static char *create_unique_id(struct kmem_cache *s)
*p++ = '-';
p += sprintf(p, "%07u", s->size);
Hm but sprintf() will happily overflow, so if we only detect that
afterwards, it's kinda too late to gracefully fail.
Should use snprintf() then?
Correct.
Updated in v2.
Thanks,
- BUG_ON(p > name + ID_STR_LENGTH - 1);
+ if (p > name + ID_STR_LENGTH - 1) {
+ kfree(name);
+ return ERR_PTR(-EINVAL);
+ }
return name;
}