Vaibhav Jain <vaib...@linux.vnet.ibm.com> writes:
> There is an unsafe signed to unsigned conversion in set_thread_tidr()
> that may cause an error value to be assigned to SPRN_TIDR register and
> used as thread-id.
>
> The issue happens as assign_thread_tidr() returns an int and
> thread.tidr is an unsigned-long. So a negative error code returned
> from assign_thread_tidr() will fail the error check and gets assigned
> as tidr as a large positive value.
>
> To fix this the patch assigns the return value of assign_thread_tidr()
> to a temporary int and assigns it to thread.tidr iff its '> 0'.
>
> The patch shouldn't impact the calling convention of set_thread_tidr()
But it does? I'm really confused.
Please fix and resend.
cheers
> int set_thread_tidr(struct task_struct *t)
> {
> + int rc;
> +
> if (!cpu_has_feature(CPU_FTR_ARCH_300))
> return -EINVAL;
^
-ve error
>
> if (t != current)
> return -EINVAL;
^
-ve error
>
> - t->thread.tidr = assign_thread_tidr();
> - if (t->thread.tidr < 0)
> - return t->thread.tidr;
^
-ve error
Yes I know we never hit that case because of the bug, that is what this
patch should be fixing, and only that.
> -
> - mtspr(SPRN_TIDR, t->thread.tidr);
> + rc = assign_thread_tidr();
> + if (rc > 0) {
> + t->thread.tidr = rc;
> + mtspr(SPRN_TIDR, t->thread.tidr);
> + }
>
> - return 0;
Success == 0
> + return rc;
Success == +ve TIDR
> }
cheers
