linux-kernel - Re: [PATCH] mm: hugetlb: undo change to page mapcount in fault handler

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 23 Dec 2011 21:00:41 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] mm: hugetlb: undo change to page mapcount in fault handler

On Fri, Dec 23, 2011 at 12:36 AM, Michal Hocko <mhocko@...e.cz> wrote:
>
> The changelog is rather cryptic. What about something like:
>

It is included in the following version, thanks.

===CUT HERE===
From: Hillf Danton <dhillf@...il.com>
Subject: [PATCH] mm: hugetlb: undo change to page mapcount in fault handler

Page mapcount should be updated only if we are sure that the page ends
up in the page table otherwise we would leak if we couldn't COW due to
reservations or if idx is out of bounds.

Signed-off-by: Hillf Danton <dhillf@...il.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Michal Hocko <mhocko@...e.cz>
---

--- a/mm/hugetlb.c	Tue Dec 20 21:26:30 2011
+++ b/mm/hugetlb.c	Thu Dec 22 21:29:42 2011
@@ -2509,6 +2509,7 @@ static int hugetlb_no_page(struct mm_str
 {
 	struct hstate *h = hstate_vma(vma);
 	int ret = VM_FAULT_SIGBUS;
+	int anon_rmap = 0;
 	pgoff_t idx;
 	unsigned long size;
 	struct page *page;
@@ -2563,14 +2564,13 @@ retry:
 			spin_lock(&inode->i_lock);
 			inode->i_blocks += blocks_per_huge_page(h);
 			spin_unlock(&inode->i_lock);
-			page_dup_rmap(page);
 		} else {
 			lock_page(page);
 			if (unlikely(anon_vma_prepare(vma))) {
 				ret = VM_FAULT_OOM;
 				goto backout_unlocked;
 			}
-			hugepage_add_new_anon_rmap(page, vma, address);
+			anon_rmap = 1;
 		}
 	} else {
 		/*
@@ -2583,7 +2583,6 @@ retry:
 			      VM_FAULT_SET_HINDEX(h - hstates);
 			goto backout_unlocked;
 		}
-		page_dup_rmap(page);
 	}

 	/*
@@ -2607,6 +2606,10 @@ retry:
 	if (!huge_pte_none(huge_ptep_get(ptep)))
 		goto backout;

+	if (anon_rmap)
+		hugepage_add_new_anon_rmap(page, vma, address);
+	else
+		page_dup_rmap(page);
 	new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
 				&& (vma->vm_flags & VM_SHARED)));
 	set_huge_pte_at(mm, address, ptep, new_pte);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/