[PATCH] fat: Fix for invalid cluster sizes

[Gedare Bloom]

ok

On Thu, May 19, 2016 at 5:55 AM, Sebastian Huber
<sebastian.huber at embedded-brains.de> wrote:
> A cluster size > 32KiB resulted in an infinite loop in
> fat_init_volume_info() due to an integer overflow.
>
> Close #2717.
> ---
>  cpukit/libfs/src/dosfs/fat.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/cpukit/libfs/src/dosfs/fat.c b/cpukit/libfs/src/dosfs/fat.c
> index 59f5309..2176ff3 100644
> --- a/cpukit/libfs/src/dosfs/fat.c
> +++ b/cpukit/libfs/src/dosfs/fat.c
> @@ -574,12 +574,14 @@ fat_init_volume_info(fat_fs_info_t *fs_info, const char *device)
>      /*
>       * "bytes per cluster" value greater than 32K is invalid
>       */
> -    if ((vol->bpc = vol->bps << vol->spc_log2) > MS_BYTES_PER_CLUSTER_LIMIT)
> +    if (vol->bps > (MS_BYTES_PER_CLUSTER_LIMIT >> vol->spc_log2))
>      {
>          close(vol->fd);
>          rtems_set_errno_and_return_minus_one(EINVAL);
>      }
>
> +    vol->bpc = vol->bps << vol->spc_log2;
> +
>      for (vol->bpc_log2 = 0, i = vol->bpc; (i & 1) == 0;
>           i >>= 1, vol->bpc_log2++);
>
> --
> 1.8.4.5
>
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