[PATCH] D119816: Fix not working attribute no_sanitize bounds that affects linux kernel

[Tong Zhang via Phabricator via llvm-commits]

ztong0001 added a comment.

In D119816#3331658 <https://reviews.llvm.org/D119816#3331658>, @nlopes wrote:

> Well, this patch is just a band-aid and a disaster waiting to happen.
> If kmalloc is tagged with an `__attribute__` stating the allocation size, then you can't dereference beyond that limit or risk the alias analysis do something you don't want. You are triggering UB like that.
> Can't you just remove the `__attribute__` from kmalloc instead to avoid triggering UB?

I am not sure I fully get what you are saying.
What I am suggesting is something like below to avoid bounds check pass from running on this function.

  diff --git a/net/core/skbuff.c b/net/core/skbuff.c
  index 9d0388bed0c1..186fca35266d 100644
  --- a/net/core/skbuff.c
  +++ b/net/core/skbuff.c
  @@ -1679,7 +1679,7 @@ EXPORT_SYMBOL(__pskb_copy_fclone);
    *     All the pointers pointing into skb header may change and must be
    *     reloaded after call to this function.
    */
  -
  +__attribute__((no_sanitize("bounds")))
   int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
                       gfp_t gfp_mask)
   {


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  https://reviews.llvm.org/D119816/new/

https://reviews.llvm.org/D119816