linux-kernel - [PATCH 3.11 76/94] mm/pagewalk.c: fix walk_page

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Date:	Fri,  8 Nov 2013 22:52:22 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Liu ShuoX <shuox.liu@...el.com>,
	Chen LinX <linx.z.chen@...el.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.11 76/94] mm/pagewalk.c: fix walk_page_range() access of wrong PTEs

3.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chen LinX <linx.z.chen@...el.com>

commit 3017f079efd6af199b0852b5c425364513db460e upstream.

When walk_page_range walk a memory map's page tables, it'll skip
VM_PFNMAP area, then variable 'next' will to assign to vma->vm_end, it
maybe larger than 'end'.  In next loop, 'addr' will be larger than
'next'.  Then in /proc/XXXX/pagemap file reading procedure, the 'addr'
will growing forever in pagemap_pte_range, pte_to_pagemap_entry will
access the wrong pte.

  BUG: Bad page map in process procrank  pte:8437526f pmd:785de067
  addr:9108d000 vm_flags:00200073 anon_vma:f0d99020 mapping:  (null) index:9108d
  CPU: 1 PID: 4974 Comm: procrank Tainted: G    B   W  O 3.10.1+ #1
  Call Trace:
    dump_stack+0x16/0x18
    print_bad_pte+0x114/0x1b0
    vm_normal_page+0x56/0x60
    pagemap_pte_range+0x17a/0x1d0
    walk_page_range+0x19e/0x2c0
    pagemap_read+0x16e/0x200
    vfs_read+0x84/0x150
    SyS_read+0x4a/0x80
    syscall_call+0x7/0xb

Signed-off-by: Liu ShuoX <shuox.liu@...el.com>
Signed-off-by: Chen LinX <linx.z.chen@...el.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/pagewalk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -242,7 +242,7 @@ int walk_page_range(unsigned long addr,
 		if (err)
 			break;
 		pgd++;
-	} while (addr = next, addr != end);
+	} while (addr = next, addr < end);

 	return err;
 }

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