From aca7573fde95152378361cba734996b384f3b1d3 Mon Sep 17 00:00:00 2001 From: Vaibhav Jain Date: Tue, 28 Nov 2017 08:23:04 +0530 Subject: [PATCH] powerpc: Avoid signed to unsigned conversion in set_thread_tidr() 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 Reviewed-by: Christophe Lombard clombard@linux.vnet.ibm.com Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/process.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index bfdd783..d205b52 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1569,16 +1569,19 @@ 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; + rc = assign_thread_tidr(); + if (rc < 0) + return rc; + t->thread.tidr = rc; mtspr(SPRN_TIDR, t->thread.tidr); return 0; -- 2.7.4