Re: [PATCH 1/1] net/mlx4: Fix build error use array_size() helper in copy_to_user()

Kees Cook
2023-01-13T18:41:10Z

On Mon, Jan 09, 2023 at 09:51:18AM -0400, Jason Gunthorpe wrote:
> On Sat, Jan 07, 2023 at 03:27:25PM +0800, Yupeng Li wrote:
> > When CONFIG_64BIT was disabled, check_copy_size() was declared with
> > attribute error: copy source size is too small, array_size() for 32BIT
> > was wrong size, some compiled msg with error like:
> >
> > CALL scripts/checksyscalls.sh
> > CC [M] drivers/net/ethernet/mellanox/mlx4/cq.o
> > In file included from ./arch/x86/include/asm/preempt.h:7,
> > from ./include/linux/preempt.h:78,
> > from ./include/linux/percpu.h:6,
> > from ./include/linux/context_tracking_state.h:5,
> > from ./include/linux/hardirq.h:5,
> > from drivers/net/ethernet/mellanox/mlx4/cq.c:37:
> > In function ‘check_copy_size’,
> > inlined from ‘copy_to_user’ at ./include/linux/uaccess.h:168:6,
> > inlined from ‘mlx4_init_user_cqes’ at drivers/net/ethernet/mellanox/mlx4/cq.c:317:9,
> > inlined from ‘mlx4_cq_alloc’ at drivers/net/ethernet/mellanox/mlx4/cq.c:394:10:
> > ./include/linux/thread_info.h:228:4: error: call to ‘__bad_copy_from’ declared with attribute error: copy source size is too small
> > 228 | __bad_copy_from();
> > | ^~~~~~~~~~~~~~~~~
> > make[6]: *** [scripts/Makefile.build:250：drivers/net/ethernet/mellanox/mlx4/cq.o] 错误 1
> > make[5]: *** [scripts/Makefile.build:500：drivers/net/ethernet/mellanox/mlx4] 错误 2
> > make[5]: *** 正在等待未完成的任务....
> > make[4]: *** [scripts/Makefile.build:500：drivers/net/ethernet/mellanox] 错误 2
> > make[3]: *** [scripts/Makefile.build:500：drivers/net/ethernet] 错误 2
> > make[3]: *** 正在等待未完成的任务....
> > make[2]: *** [scripts/Makefile.build:500：drivers/net] 错误 2
> > make[2]: *** 正在等待未完成的任务....
> > make[1]: *** [scripts/Makefile.build:500：drivers] 错误 2
> > make: *** [Makefile:1992：.] 错误 2
> >
> > Signed-off-by: Yupeng Li <liyupeng@zbhlos.com>
> > Reviewed-by: Caicai <caizp2008@163.com>
> > ---
> > drivers/net/ethernet/mellanox/mlx4/cq.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
> > index 4d4f9cf9facb..7dadd7227480 100644
> > --- a/drivers/net/ethernet/mellanox/mlx4/cq.c
> > +++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
> > @@ -315,7 +315,11 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
> > }
> > } else {
> > err = copy_to_user((void __user *)buf, init_ents,
> > +#ifdef CONFIG_64BIT
> > array_size(entries, cqe_size)) ?
> > +#else
> > + entries * cqe_size) ?
> > +#endif
> > -EFAULT : 0;
>
> This can't possibly make sense, Kees?

Uuuuh, that's really weird. What compiler version and arch? I'll see if
I can reproduce this.

--
Kees Cook