From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f177.google.com (mail-wi0-f177.google.com [209.85.212.177]) by kanga.kvack.org (Postfix) with ESMTP id A539D6B00DB for ; Thu, 13 Nov 2014 09:55:26 -0500 (EST) Received: by mail-wi0-f177.google.com with SMTP id l15so4625245wiw.4 for ; Thu, 13 Nov 2014 06:55:26 -0800 (PST) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id vm10si29127280wjc.57.2014.11.13.06.55.25 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Thu, 13 Nov 2014 06:55:25 -0800 (PST) Date: Thu, 13 Nov 2014 15:55:13 +0100 (CET) From: Thomas Gleixner Subject: Re: [PATCH 10/11] x86, mpx: cleanup unused bound tables In-Reply-To: <20141112170512.C932CF4D@viggo.jf.intel.com> Message-ID: References: <20141112170443.B4BD0899@viggo.jf.intel.com> <20141112170512.C932CF4D@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: hpa@zytor.com, mingo@redhat.com, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@linux-mips.org, qiaowei.ren@intel.com, dave.hansen@linux.intel.com On Wed, 12 Nov 2014, Dave Hansen wrote: > +/* > + * Get the base of bounds tables pointed by specific bounds > + * directory entry. > + */ > +static int get_bt_addr(struct mm_struct *mm, > + long __user *bd_entry, unsigned long *bt_addr) > +{ > + int ret; > + int valid; > + > + if (!access_ok(VERIFY_READ, (bd_entry), sizeof(*bd_entry))) > + return -EFAULT; > + > + while (1) { > + int need_write = 0; > + > + pagefault_disable(); > + ret = get_user(*bt_addr, bd_entry); > + pagefault_enable(); > + if (!ret) > + break; > + if (ret == -EFAULT) > + ret = mpx_resolve_fault(bd_entry, need_write); > + /* > + * If we could not resolve the fault, consider it > + * userspace's fault and error out. > + */ > + if (ret) > + return ret; > + } > + > + valid = *bt_addr & MPX_BD_ENTRY_VALID_FLAG; > + *bt_addr &= MPX_BT_ADDR_MASK; > + > + /* > + * When the kernel is managing bounds tables, a bounds directory > + * entry will either have a valid address (plus the valid bit) > + * *OR* be completely empty. If we see a !valid entry *and* some > + * data in the address field, we know something is wrong. This > + * -EINVAL return will cause a SIGSEGV. > + */ > + if (!valid && *bt_addr) > + return -EINVAL; > + /* > + * Not present is OK. It just means there was no bounds table > + * for this memory, which is completely OK. Make sure to distinguish > + * this from -EINVAL, which will cause a SEGV. > + */ > + if (!valid) > + return -ENOENT; So here you have the extra -ENOENT return value, but at the direct/indirect call sites you ignore -EINVAL or everything. > +static int mpx_unmap_tables(struct mm_struct *mm, > + unsigned long start, unsigned long end) > + ret = unmap_edge_bts(mm, start, end); > + if (ret == -EFAULT) > + return ret; So here you ignore EINVAL despite claiming that it will cause a SIGSEGV. So this should be: switch (ret) { case 0: case -ENOENT: break; default: return ret; } > + for (bd_entry = bde_start + 1; bd_entry < bde_end; bd_entry++) { > + ret = get_bt_addr(mm, bd_entry, &bt_addr); > + /* > + * If we encounter an issue like a bad bounds-directory > + * we should still try the next one. > + */ > + if (ret) > + continue; You ignore all error returns. switch (ret) { case 0: break; case -ENOENT: continue; default: return ret; } Other than that, this all looks very reasonable now. Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org