Re: [PATCH] sg: fix overflow in timeout calculation

[Douglas Gilbert <dgilbert@interlog.com>]

On 15-02-09 01:45 PM, Mikulas Patocka wrote:
> USER_HZ may be greater than HZ and in that case arithmetics tries to
> calculate the maximum accepted timeout overflows. We need to use INT_MAX
> in this case.
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Cc: stable@vger.kernel.org

Acked-by: Douglas Gilbert <dgilbert@interlog.com>

> ---
>   drivers/scsi/sg.c |   10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> Index: linux-3.17-rc6/drivers/scsi/sg.c
> ===================================================================
> --- linux-3.17-rc6.orig/drivers/scsi/sg.c	2014-09-26 20:10:22.000000000 +0200
> +++ linux-3.17-rc6/drivers/scsi/sg.c	2014-09-26 20:10:50.000000000 +0200
> @@ -90,6 +90,12 @@ static void sg_proc_cleanup(void);
>    */
>   #define MULDIV(X,MUL,DIV) ((((X % DIV) * MUL) / DIV) + ((X / DIV) * MUL))
>
> +#if USER_HZ < HZ
> +#define MAX_USER_TIMEOUT MULDIV (INT_MAX, USER_HZ, HZ)
> +#else
> +#define MAX_USER_TIMEOUT INT_MAX
> +#endif
> +
>   #define SG_DEFAULT_TIMEOUT MULDIV(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ)
>
>   int sg_big_buff = SG_DEF_RESERVED_SIZE;
> @@ -892,8 +898,8 @@ sg_ioctl(struct file *filp, unsigned int
>   			return result;
>   		if (val < 0)
>   			return -EIO;
> -		if (val >= MULDIV (INT_MAX, USER_HZ, HZ))
> -		    val = MULDIV (INT_MAX, USER_HZ, HZ);
> +		if (val >= MAX_USER_TIMEOUT)
> +		    val = MAX_USER_TIMEOUT;
>   		sfp->timeout_user = val;
>   		sfp->timeout = MULDIV (val, HZ, USER_HZ);
>
> --