Re: [RFC] net: fix data race on sk_buff after re-cloning

[Eric Dumazet]

On Thu, 2015-09-17 at 20:44 +0200, Dmitry Vyukov wrote:
> KernelThreadSanitizer (KTSAN) reported the following race (on 4.2 rc2):
> 
> ThreadSanitizer: data-race in __copy_skb_header
...

> 	if (likely(atomic_read(&skb->users) == 1))
> 		smp_rmb();
> 
> The patch contains a proposed fix.
> If it looks good to you and the scenario looks sane,
> then I will update the description and resend it.
> ---
>  net/core/skbuff.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

I have to double check this patch, but in the case it is needed,
it would be better to not use fancy new atomic_read_acquire(),
as backporting the fix up to 3.19 (where the bug was probably added)
will require extra hassle.

atomic_read_acquire() would be fine for cleanups and new code, in next
branch.

Thanks !


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