Re: [PATCH] s390/uprobes: Fix off-by-one bug in emulated PER handling

[Sven Schnelle <svens@linux.ibm.com>]

Heiko Carstens <hca@linux.ibm.com> writes:

> The uprobes code emulates some instructions, and with that also
> PER storage-alteration handling, in case a debugger is attached.
>
> The PER storage-alteration handling contains an off-by-one bug, which
> may lead to PER traps which should not happen. Adjust the comparison
> in sim_stor_event() to fix that.
>
> Fixes: 8d1a2427d8fc ("s390/uprobes: fix user space PER events")
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>  arch/s390/kernel/uprobes.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/s390/kernel/uprobes.c b/arch/s390/kernel/uprobes.c
> index c624f3361e43..b2b8a377ced6 100644
> --- a/arch/s390/kernel/uprobes.c
> +++ b/arch/s390/kernel/uprobes.c
> @@ -241,7 +241,7 @@ static void sim_stor_event(struct pt_regs *regs, void *addr, int len)
>  		return;
>  	if (!(current->thread.per_user.control & PER_EVENT_STORE))
>  		return;
> -	if ((void *)current->thread.per_user.start > (addr + len))
> +	if ((void *)current->thread.per_user.start > (addr + len - 1))
>  		return;
>  	if ((void *)current->thread.per_user.end < addr)
>  		return;

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>