On Mon, Aug 10, 2020 at 08:41:14PM +0200, Marion & Christophe JAILLET wrote:
>
> Le 10/08/2020 à 17:42, Dan Carpenter a écrit :
> > On Sun, Aug 09, 2020 at 10:34:06PM +0200, Christophe JAILLET wrote:
> > > When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
> > > of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
> > > 'sgt' (i.e struct sg_table), so this could lead to memory corruption.
> > The sizeof(*sg) is bigger than sizeof(**sgt) so this wastes memory but
> > it won't lead to corruption.
> >
> > 11 struct scatterlist {
> > 12 unsigned long page_link;
> > 13 unsigned int offset;
> > 14 unsigned int length;
> > 15 dma_addr_t dma_address;
> > 16 #ifdef CONFIG_NEED_SG_DMA_LENGTH
> > 17 unsigned int dma_length;
> > 18 #endif
> > 19 };
> >
> > 42 struct sg_table {
> > 43 struct scatterlist *sgl; /* the list */
> > 44 unsigned int nents; /* number of mapped entries */
> > 45 unsigned int orig_nents; /* original size of list */
> > 46 };
> >
> > regards,
> > dan carpenter
>
>
> My bad. I read 'struct scatterlist sgl' (without the *)
> Thanks for the follow-up, Dan.
>
> Doesn't smatch catch such mismatch?
> (I've not run smatch for a while, so it is maybe reported)
That's why I was investigating it, because Smatch didn't catch it.
Smatch would have warned if it led to memory corruption. Smatch also
tries to detect struct mismatches as a separate check but for some
reason it missed it. I'm not totally sure why yet. I suspect that it's
a complicated internal reason where Sparse is the sizeof to a normal
number... It's a known issue and hard to fix.
>
> Well, the proposal is still valid, even if it has less impact as initially
> thought.
Yep.
regards,
dan carpenter
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