Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762272AbYBLLay (ORCPT ); Tue, 12 Feb 2008 06:30:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754724AbYBLLaq (ORCPT ); Tue, 12 Feb 2008 06:30:46 -0500 Received: from mx1.redhat.com ([66.187.233.31]:54040 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760276AbYBLLap (ORCPT ); Tue, 12 Feb 2008 06:30:45 -0500 Date: Tue, 12 Feb 2008 19:28:31 +0800 From: Eugene Teo To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, corbet@lwn.net Subject: [PATCH 1/2] mm: make get_user_pages() more robust in handling arguments Message-ID: <20080212112831.GA3481@kernel.sg> Reply-To: Eugene Teo MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4739 Lines: 141 Ensure that get_user_pages() evaluates len upon entry into the while loops. A BUG_ON check is added so that it will catch potential bugs when it is asked to grab zero pages. follow_hugetlb_page() is modified to adapt the changes made in get_user_pages(). Signed-off-by: Eugene Teo --- include/linux/hugetlb.h | 2 +- mm/hugetlb.c | 10 +++------- mm/memory.c | 15 ++++++--------- 3 files changed, 10 insertions(+), 17 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 7ca198b..2e8a01d 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -20,7 +20,7 @@ int hugetlb_sysctl_handler(struct ctl_table *, int, struct file *, void __user * int hugetlb_overcommit_handler(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *); int hugetlb_treat_movable_handler(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *); int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *); -int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, unsigned long *, int *, int, int); +int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, unsigned long *, int, int, int); void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long); void __unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long); int hugetlb_prefault(struct address_space *, struct vm_area_struct *); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index d9a3803..5bb8130 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -960,15 +960,14 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, struct page **pages, struct vm_area_struct **vmas, - unsigned long *position, int *length, int i, + unsigned long *position, int length, int i, int write) { unsigned long pfn_offset; unsigned long vaddr = *position; - int remainder = *length; spin_lock(&mm->page_table_lock); - while (vaddr < vma->vm_end && remainder) { + while (i < length && vaddr < vma->vm_end) { pte_t *pte; struct page *page; @@ -988,7 +987,6 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, if (!(ret & VM_FAULT_ERROR)) continue; - remainder = 0; if (!i) i = -EFAULT; break; @@ -1007,9 +1005,8 @@ same_page: vaddr += PAGE_SIZE; ++pfn_offset; - --remainder; ++i; - if (vaddr < vma->vm_end && remainder && + if (i < length && vaddr < vma->vm_end && pfn_offset < HPAGE_SIZE/PAGE_SIZE) { /* * We use pfn_offset to avoid touching the pageframes @@ -1019,7 +1016,6 @@ same_page: } } spin_unlock(&mm->page_table_lock); - *length = remainder; *position = vaddr; return i; diff --git a/mm/memory.c b/mm/memory.c index 717aa0e..54f951b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -989,8 +989,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, int i; unsigned int vm_flags; - if (len <= 0) - return 0; + BUG_ON(len <= 0); /* * Require read or write permissions. * If 'force' is set, we only require the "MAY" flags. @@ -999,7 +998,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE); i = 0; - do { + while (i < len) { struct vm_area_struct *vma; unsigned int foll_flags; @@ -1039,7 +1038,6 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, vmas[i] = gate_vma; i++; start += PAGE_SIZE; - len--; continue; } @@ -1049,7 +1047,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, if (is_vm_hugetlb_page(vma)) { i = follow_hugetlb_page(mm, vma, pages, vmas, - &start, &len, i, write); + &start, len, i, write); continue; } @@ -1061,7 +1059,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, !vma->vm_ops->fault))) foll_flags |= FOLL_ANON; - do { + while (i < len && start < vma->vm_end) { struct page *page; /* @@ -1114,9 +1112,8 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, vmas[i] = vma; i++; start += PAGE_SIZE; - len--; - } while (len && start < vma->vm_end); - } while (len); + } + } return i; } EXPORT_SYMBOL(get_user_pages); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/