From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3yltqH2gqWzDr5b for ; Tue, 28 Nov 2017 04:20:42 +1100 (AEDT) Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id vARHK6lN028659 for ; Mon, 27 Nov 2017 12:20:41 -0500 Received: from e06smtp12.uk.ibm.com (e06smtp12.uk.ibm.com [195.75.94.108]) by mx0a-001b2d01.pphosted.com with ESMTP id 2egn99dset-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 27 Nov 2017 12:20:40 -0500 Received: from localhost by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 27 Nov 2017 17:20:37 -0000 From: Vaibhav Jain To: linuxppc-dev@lists.ozlabs.org, Sukadev Bhattiprolu , Christophe Lombard , Philippe Bergheaud , Michael Ellerman Cc: Vaibhav Jain , Frederic Barrat , Andrew Donnellan , "Alastair D'Silva" Subject: [PATCH v3] powerpc: Avoid signed to unsigned conversion in set_thread_tidr() Date: Mon, 27 Nov 2017 22:49:35 +0530 Message-Id: <20171127171935.21364-1-vaibhav@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 --- Changelog: v3 -> Updated the patch to not impact the calling convention [Mpe, Christophe] v2 -> * Update the patch description to document the calling convention of set_thread_tidr(). [Mpe] * Fix a tidr allocation leak. --- arch/powerpc/kernel/process.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index bfdd783e3916..9fb69211a3d4 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1569,19 +1569,22 @@ 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); - - return 0; + rc = assign_thread_tidr(); + if (rc > 0) { + t->thread.tidr = rc; + mtspr(SPRN_TIDR, t->thread.tidr); + return 0; + } else { + return rc; + } } #endif /* CONFIG_PPC64 */ -- 2.14.3