Re: [PATCH] cxl/pmem: Use size_add() against integer overflow

[Yu Zhe]

在 2022年09月28日 00:23, Ira Weiny 写道:

> On Tue, Sep 27, 2022 at 12:02:47AM -0700, Yu Zhe wrote:
> > "struct_size() + n" may cause a integer overflow,
> > use size_add() to handle it.
> >
> > Signed-off-by: Yu Zhe <yuzhe@xxxxxxxxxxxx>
> > ---
> >   drivers/cxl/pmem.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> > index 7dc0a2fa1a6b..8c08aa009a56 100644
> > --- a/drivers/cxl/pmem.c
> > +++ b/drivers/cxl/pmem.c
> > @@ -148,7 +148,7 @@ static int cxl_pmem_set_config_data(struct cxl_dev_state *cxlds,
> >   		return -EINVAL;
> >   
> >   	/* 4-byte status follows the input data in the payload */
> > -	if (struct_size(cmd, in_buf, cmd->in_length) + 4 > buf_len)
> > +	if (size_add(struct_size(cmd, in_buf, cmd->in_length), 4) > buf_len)
> I don't see any benefit here.
>
> struct_size() calls __ab_c_size() which already calls check_add_overflow()?  So
> why wrap that in another check?
"struct_size() + 4" still might cause overflow, so there need to use 
"size_add" to check it.
> Were you able to get this to fail with some user input?
>
> Ira
>
> >   		return -EINVAL;
> >   
> >   	set_lsa =
> > --
> > 2.11.0