Re: [PATCH v2] mm/slub: clean up create_unique_id()
From: Chao Yu
Date: Mon Sep 26 2022 - 04:24:30 EST
On 2022/9/26 16:22, Vlastimil Babka wrote:
On 9/25/22 09:12, 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. use WARN_ON instead of BUG_ON() and return error if check condition
is true;
3. use snprintf instead of sprintf to avoid overflow.
Link: https://lore.kernel.org/linux-mm/2025305d-16db-abdf-6cd3-1fb93371c2b4@xxxxxxxxxx/
Fixes: 81819f0fc828 ("SLUB core")
Suggested-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Signed-off-by: Chao Yu <chao.yu@xxxxxxxx>
---
v2:
- add WARN_ON() instead of return error silently;
- use snprintf instead of sprintf to avoid overflow.
mm/slub.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 4b98dff9be8e..3d37a8a7b965 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5890,7 +5890,7 @@ 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:
*
@@ -5924,9 +5924,13 @@ 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 - 1 - (p - name), "%07u", s->size);
I think we don't need "- 1" here as snprintf() says:
@size: The size of the buffer, including the trailing null space
Oops, my bad.
- BUG_ON(p > name + ID_STR_LENGTH - 1);
+ if (p > name + ID_STR_LENGTH - 1) {
+ WARN_ON(1);
This would be shorter: if (WARN_ON(p > name...))
Thanks for the comments, will update soon.
Thanks,
+ kfree(name);
+ return ERR_PTR(-EINVAL);
+ }
return name;
}