Re: [v4] powerpc: Avoid signed to unsigned conversion in set_thread_tidr()

On Tue, 2017-11-28 at 02:53:04 UTC, Vaibhav Jain wrote:

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()
i.e all -ve return-values are error codes and a return value of '0'
indicates success.

Fixes: ec233ede4c86("powerpc: Add support for setting SPRN_TIDR")
Signed-off-by: Vaibhav Jain <redacted>
Reviewed-by: Christophe Lombard clombard@linux.vnet.ibm.com

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/aca7573fde95152378361cba734996

cheers