linux-kernel - RE: skb_to_sgvec() causes sg_pcopy_to

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Message-ID: <0835B3720019904CB8F7AA43166CEEB2F18A049D@RTITMBSVM03.realtek.com.tw>
Date:   Fri, 21 Jun 2019 07:37:52 +0000
From:   Hayes Wang <hayeswang@...ltek.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        nic_swsd <nic_swsd@...ltek.com>
Subject: RE: skb_to_sgvec() causes sg_pcopy_to_buffer() wrong

> Use skb_to_sgvec() to set scatter list, and sometime we would get a
> sg->offset which is more than PAGE_SIZE. Call sg_pcopy_to_buffer()
> with this scatter list would get wrong data.
> 
> In sg_miter_get_next_page(), you would get wrong miter->__remaining,
> when the sg->offset is more than PAGE_SIZE.
> 
> static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
> {
> 	if (!miter->__remaining) {
> 		struct scatterlist *sg;
> 		unsigned long pgoffset;
> 
> 		if (!__sg_page_iter_next(&miter->piter))
> 			return false;
> 
> 		sg = miter->piter.sg;
> 		pgoffset = miter->piter.sg_pgoffset;
> 
> 		miter->__offset = pgoffset ? 0 : sg->offset;
> 		miter->__remaining = sg->offset + sg->length -
> 				(pgoffset << PAGE_SHIFT) - miter->__offset;
> 		miter->__remaining = min_t(unsigned long, miter->__remaining,
> 					   PAGE_SIZE - miter->__offset);
> 	}
> 
> 	return true;
> }

Excuse me. The following patch could solve my problem.

https://patchwork.kernel.org/patch/11000549/

Best Regards,
Hayes