skb_to_sgvec() casuses sg_pcopy_to_buffer() wrong

From: Hayes Wang
Date: Thu Jun 20 2019 - 02:22:32 EST

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->;
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;

Best Regards,