On Thu, Sep 30, 2021 at 03:26:57PM -0700, Kees Cook wrote:
> After adding __alloc_size attributes to the allocators, GCC 9.3 (but not
> later) may incorrectly evaluate the arguments to check_copy_size(),
> getting seemingly confused by the size being returned from array_size().
> Instead, perform the calculation once, which both makes the code more
> readable and avoids the bug in GCC.
>
> In file included from arch/x86/include/asm/preempt.h:7,
> from include/linux/preempt.h:78,
> from include/linux/spinlock.h:55,
> from include/linux/mm_types.h:9,
> from include/linux/buildid.h:5,
> from include/linux/module.h:14,
> from drivers/rapidio/devices/rio_mport_cdev.c:13:
> In function 'check_copy_size',
> inlined from 'copy_from_user' at include/linux/uaccess.h:191:6,
> inlined from 'rio_mport_transfer_ioctl' at drivers/rapidio/devices/rio_mport_cdev.c:983:6:
> include/linux/thread_info.h:213:4: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small
> 213 | __bad_copy_to();
> | ^~~~~~~~~~~~~~~
>
> But the allocation size and the copy size are identical:
>
> transfer = vmalloc(array_size(sizeof(*transfer), transaction.count));
> if (!transfer)
> return -ENOMEM;
>
> if (unlikely(copy_from_user(transfer,
> (void __user *)(uintptr_t)transaction.block,
> array_size(sizeof(*transfer), transaction.count)))) {
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Link: https://lore.kernel.org/linux-mm/202109091134.FHnRmRxu-lkp@xxxxxxxxx/
> Cc: Matt Porter <mporter@xxxxxxxxxxxxxxxxxxx>
> Cc: Alexandre Bounine <alex.bou9@xxxxxxxxx>
> Cc: Jing Xiangfeng <jingxiangfeng@xxxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Cc: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Thanks
--
Gustavo
> ---
> drivers/rapidio/devices/rio_mport_cdev.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
> index 94331d999d27..7df466e22282 100644
> --- a/drivers/rapidio/devices/rio_mport_cdev.c
> +++ b/drivers/rapidio/devices/rio_mport_cdev.c
> @@ -965,6 +965,7 @@ static int rio_mport_transfer_ioctl(struct file *filp, void __user *arg)
> struct rio_transfer_io *transfer;
> enum dma_data_direction dir;
> int i, ret = 0;
> + size_t size;
>
> if (unlikely(copy_from_user(&transaction, arg, sizeof(transaction))))
> return -EFAULT;
> @@ -976,13 +977,14 @@ static int rio_mport_transfer_ioctl(struct file *filp, void __user *arg)
> priv->md->properties.transfer_mode) == 0)
> return -ENODEV;
>
> - transfer = vmalloc(array_size(sizeof(*transfer), transaction.count));
> + size = array_size(sizeof(*transfer), transaction.count);
> + transfer = vmalloc(size);
> if (!transfer)
> return -ENOMEM;
>
> if (unlikely(copy_from_user(transfer,
> (void __user *)(uintptr_t)transaction.block,
> - array_size(sizeof(*transfer), transaction.count)))) {
> + size))) {
> ret = -EFAULT;
> goto out_free;
> }
> @@ -994,8 +996,7 @@ static int rio_mport_transfer_ioctl(struct file *filp, void __user *arg)
> transaction.sync, dir, &transfer[i]);
>
> if (unlikely(copy_to_user((void __user *)(uintptr_t)transaction.block,
> - transfer,
> - array_size(sizeof(*transfer), transaction.count))))
> + transfer, size)))
> ret = -EFAULT;
>
> out_free:
> --
> 2.30.2
>
