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'.
.. and changes the calling convention of the function. Now it returns -ve error values, or a +ve TIDR value when it succeeds, or possibly 0 if that's returned by assign_thread_tidr(). Which I'm not sure you meant to do. If you did, you should at least document it. But frankly I'd rather we left it the way it was, -ve error or 0 for success. cheers > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index bfdd783e3916..a6eaf924c8b6 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -1569,19 +1569,21 @@ void arch_release_task_struct(struct task_struct *t) > */ > int set_thread_tidr(struct task_struct *t) > { > + int rc; > + > if (!cpu_has_feature(CPU_FTR_ARCH_300)) > return -EINVAL; > > if (t != current) > return -EINVAL; > > - t->thread.tidr = assign_thread_tidr(); > - if (t->thread.tidr < 0) > - return t->thread.tidr; > - > - mtspr(SPRN_TIDR, t->thread.tidr); > + rc = assign_thread_tidr(); > + if (rc > 0) { > + t->thread.tidr = assign_thread_tidr(); > + mtspr(SPRN_TIDR, t->thread.tidr); > + } > > - return 0; > + return rc; > } > > #endif /* CONFIG_PPC64 */ > -- > 2.14.3