Re: [PATCH] block: fix get_max_segment_size() overflow on 32bit arch

[Ming Lei <ming.lei@redhat.com>]

On Wed, Jan 08, 2020 at 02:06:25AM +0000, Damien Le Moal wrote:
> On 2020/01/08 10:25, Ming Lei wrote:
> > Commit 429120f3df2d starts to take account of segment's start dma address
> > when computing max segment size, and data type of 'unsigned long'
> > is used to do that. However, the segment mask may be 0xffffffff, so
> > the figured out segment size may be overflowed because DMA address can
> > be 64bit on 32bit arch.
> > 
> > Fixes the issue by using 'unsigned long long' to compute max segment
> > size.
> > 
> > Fixes: 429120f3df2d ("block: fix splitting segments on boundary masks")
> > Reported-by: Guenter Roeck <linux@roeck-us.net>
> > Tested-by: Guenter Roeck <linux@roeck-us.net>
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >  block/blk-merge.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/block/blk-merge.c b/block/blk-merge.c
> > index 347782a24a35..b0fcc72594cb 100644
> > --- a/block/blk-merge.c
> > +++ b/block/blk-merge.c
> > @@ -159,12 +159,12 @@ static inline unsigned get_max_io_size(struct request_queue *q,
> >  
> >  static inline unsigned get_max_segment_size(const struct request_queue *q,
> >  					    struct page *start_page,
> > -					    unsigned long offset)
> > +					    unsigned long long offset)
> >  {
> >  	unsigned long mask = queue_segment_boundary(q);
> >  
> >  	offset = mask & (page_to_phys(start_page) + offset);
> 
> Shouldn't mask be an unsigned long long too for this to give the
> expected correct result ?

queue_segment_boundary() always returns 'unsigned long', so far not
see issue related with that.


Thanks,
Ming