linux-kernel - Re: [syzbot] [mm?] BUG: Bad page map (7)

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Date:   Mon, 11 Sep 2023 15:12:27 +0800
From:   Yin Fengwei <fengwei.yin@...el.com>
To:     syzbot <syzbot+55cc72f8cc3a549119df@...kaller.appspotmail.com>,
        <akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, <syzkaller-bugs@...glegroups.com>,
        <willy@...radead.org>
Subject: Re: [syzbot] [mm?] BUG: Bad page map (7)



On 9/10/23 01:12, syzbot wrote:
> commit 617c28ecab22d98a3809370eb6cb50fa24b7bfe1
> Author: Yin Fengwei <fengwei.yin@...el.com>
> Date:   Wed Aug 2 15:14:05 2023 +0000
> 
>     filemap: batch PTE mappings

#syz test

diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index a629b1b9f65a6..2701b47efa8f7 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -168,6 +168,28 @@ static inline void native_pgd_clear(pgd_t *pgd)
        native_set_pgd(pgd, native_make_pgd(0));
 }
 
+static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
+               pte_t *ptep, pte_t pte, unsigned int nr)
+{
+       bool protnone = (pte_flags(pte) & (_PAGE_PROTNONE | _PAGE_PRESENT))
+                       == _PAGE_PROTNONE;
+
+       page_table_check_ptes_set(mm, ptep, pte, nr);
+
+       for(;;) {
+               native_set_pte(ptep, pte);
+               if (--nr == 0)
+                       break;
+
+               ptep++;
+               if (protnone)
+                       pte = __pte(pte_val(pte) - (1UL << PFN_PTE_SHIFT));
+               else
+                       pte = __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
+       }
+}
+#define set_ptes set_ptes
+
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.