diff mbox series

[1/2] arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud

Message ID 20221116083811.464678-2-liushixin2@huawei.com
State New
Headers
Series arm64: fix two bug about page table check |

Commit Message

Liu Shixin Nov. 16, 2022, 8:38 a.m. UTC 
  The page table check trigger BUG_ON() unexpectedly when collapse hugepage:

 ------------[ cut here ]------------
 kernel BUG at mm/page_table_check.c:82!
 Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
 Dumping ftrace buffer:
    (ftrace buffer empty)
 Modules linked in:
 CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750
 Hardware name: linux,dummy-virt (DT)
 pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : page_table_check_clear.isra.0+0x258/0x3f0
 lr : page_table_check_clear.isra.0+0x240/0x3f0
[...]
 Call trace:
  page_table_check_clear.isra.0+0x258/0x3f0
  __page_table_check_pmd_clear+0xbc/0x108
  pmdp_collapse_flush+0xb0/0x160
  collapse_huge_page+0xa08/0x1080
  hpage_collapse_scan_pmd+0xf30/0x1590
  khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8
  khugepaged+0x338/0x518
  kthread+0x278/0x2f8
  ret_from_fork+0x10/0x20
[...]

Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it
decrease file_map_count for a non-leaf pmd comes from collapse_huge_page().
and so trigger BUG_ON() unexpectedly.

Fix this problem by using pmd_leaf() insteal of pmd_present() in
pmd_user_accessible_page(). Moreover, use pud_leaf() for
pud_user_accessible_page() too.

Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
Reported-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
---
 arch/arm64/include/asm/pgtable.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

David Hildenbrand Nov. 16, 2022, 9:04 a.m. UTC | #1 
On 16.11.22 09:38, Liu Shixin wrote:
> The page table check trigger BUG_ON() unexpectedly when collapse hugepage:
> 
>   ------------[ cut here ]------------
>   kernel BUG at mm/page_table_check.c:82!
>   Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>   Dumping ftrace buffer:
>      (ftrace buffer empty)
>   Modules linked in:
>   CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750
>   Hardware name: linux,dummy-virt (DT)
>   pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>   pc : page_table_check_clear.isra.0+0x258/0x3f0
>   lr : page_table_check_clear.isra.0+0x240/0x3f0
> [...]
>   Call trace:
>    page_table_check_clear.isra.0+0x258/0x3f0
>    __page_table_check_pmd_clear+0xbc/0x108
>    pmdp_collapse_flush+0xb0/0x160
>    collapse_huge_page+0xa08/0x1080
>    hpage_collapse_scan_pmd+0xf30/0x1590
>    khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8
>    khugepaged+0x338/0x518
>    kthread+0x278/0x2f8
>    ret_from_fork+0x10/0x20
> [...]
> 
> Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it
> decrease file_map_count for a non-leaf pmd comes from collapse_huge_page().
> and so trigger BUG_ON() unexpectedly.
> 
> Fix this problem by using pmd_leaf() insteal of pmd_present() in
> pmd_user_accessible_page(). Moreover, use pud_leaf() for
> pud_user_accessible_page() too.
> 
> Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
> Reported-by: Denys Vlasenko <dvlasenk@redhat.com>
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> ---
>   arch/arm64/include/asm/pgtable.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 71a1af42f0e8..edf6625ce965 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -863,12 +863,12 @@ static inline bool pte_user_accessible_page(pte_t pte)
>   
>   static inline bool pmd_user_accessible_page(pmd_t pmd)
>   {
> -	return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
> +	return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
>   }
>   
>   static inline bool pud_user_accessible_page(pud_t pud)
>   {
> -	return pud_present(pud) && pud_user(pud);
> +	return pud_leaf(pud) && pud_user(pud);
>   }
>   #endif
>   

Reviewed-by: David Hildenbrand <david@redhat.com>
Pasha Tatashin Nov. 16, 2022, 2:59 p.m. UTC | #2 
On Wed, Nov 16, 2022 at 2:51 AM Liu Shixin <liushixin2@huawei.com> wrote:
>
> The page table check trigger BUG_ON() unexpectedly when collapse hugepage:
>
>  ------------[ cut here ]------------
>  kernel BUG at mm/page_table_check.c:82!
>  Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>  Dumping ftrace buffer:
>     (ftrace buffer empty)
>  Modules linked in:
>  CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750
>  Hardware name: linux,dummy-virt (DT)
>  pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>  pc : page_table_check_clear.isra.0+0x258/0x3f0
>  lr : page_table_check_clear.isra.0+0x240/0x3f0
> [...]
>  Call trace:
>   page_table_check_clear.isra.0+0x258/0x3f0
>   __page_table_check_pmd_clear+0xbc/0x108
>   pmdp_collapse_flush+0xb0/0x160
>   collapse_huge_page+0xa08/0x1080
>   hpage_collapse_scan_pmd+0xf30/0x1590
>   khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8
>   khugepaged+0x338/0x518
>   kthread+0x278/0x2f8
>   ret_from_fork+0x10/0x20
> [...]
>
> Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it
> decrease file_map_count for a non-leaf pmd comes from collapse_huge_page().
> and so trigger BUG_ON() unexpectedly.
>
> Fix this problem by using pmd_leaf() insteal of pmd_present() in

s/insteal/instead

> pmd_user_accessible_page(). Moreover, use pud_leaf() for
> pud_user_accessible_page() too.
>
> Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
> Reported-by: Denys Vlasenko <dvlasenk@redhat.com>
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> ---
>  arch/arm64/include/asm/pgtable.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 71a1af42f0e8..edf6625ce965 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -863,12 +863,12 @@ static inline bool pte_user_accessible_page(pte_t pte)
>
>  static inline bool pmd_user_accessible_page(pmd_t pmd)
>  {
> -       return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
> +       return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
>  }
>
>  static inline bool pud_user_accessible_page(pud_t pud)
>  {
> -       return pud_present(pud) && pud_user(pud);
> +       return pud_leaf(pud) && pud_user(pud);

Thanks a lot. The x86 variants are already using p*d_leaf() in these functions.

Acked-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Anshuman Khandual Nov. 17, 2022, 4:09 a.m. UTC | #3 
On 11/16/22 14:08, Liu Shixin wrote:
> The page table check trigger BUG_ON() unexpectedly when collapse hugepage:
> 
>  ------------[ cut here ]------------
>  kernel BUG at mm/page_table_check.c:82!
>  Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>  Dumping ftrace buffer:
>     (ftrace buffer empty)
>  Modules linked in:
>  CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750
>  Hardware name: linux,dummy-virt (DT)
>  pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>  pc : page_table_check_clear.isra.0+0x258/0x3f0
>  lr : page_table_check_clear.isra.0+0x240/0x3f0
> [...]
>  Call trace:
>   page_table_check_clear.isra.0+0x258/0x3f0
>   __page_table_check_pmd_clear+0xbc/0x108
>   pmdp_collapse_flush+0xb0/0x160
>   collapse_huge_page+0xa08/0x1080
>   hpage_collapse_scan_pmd+0xf30/0x1590
>   khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8
>   khugepaged+0x338/0x518
>   kthread+0x278/0x2f8
>   ret_from_fork+0x10/0x20
> [...]
> 
> Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it
> decrease file_map_count for a non-leaf pmd comes from collapse_huge_page().
> and so trigger BUG_ON() unexpectedly.

Could you please provide the pmd_val() on the pmd entry, that triggers this
BUG_ON() here ? Only additional thing pmd_leaf() ensures, is that the entry
is not a table one.

#define pmd_leaf(pmd)           (pmd_present(pmd) && !pmd_table(pmd))

collapse_huge_page() pmd is non-leaf because it has table bit on ?

> 
> Fix this problem by using pmd_leaf() insteal of pmd_present() in
> pmd_user_accessible_page(). Moreover, use pud_leaf() for
> pud_user_accessible_page() too.
> 
> Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
> Reported-by: Denys Vlasenko <dvlasenk@redhat.com>
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> ---
>  arch/arm64/include/asm/pgtable.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 71a1af42f0e8..edf6625ce965 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -863,12 +863,12 @@ static inline bool pte_user_accessible_page(pte_t pte)
>  
>  static inline bool pmd_user_accessible_page(pmd_t pmd)
>  {
> -	return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
> +	return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
>  }
>  
>  static inline bool pud_user_accessible_page(pud_t pud)
>  {
> -	return pud_present(pud) && pud_user(pud);
> +	return pud_leaf(pud) && pud_user(pud);
>  }
>  #endif
>
Liu Shixin Nov. 17, 2022, 6:59 a.m. UTC | #4 
On 2022/11/17 12:09, Anshuman Khandual wrote:
>
> On 11/16/22 14:08, Liu Shixin wrote:
>> The page table check trigger BUG_ON() unexpectedly when collapse hugepage:
>>
>>  ------------[ cut here ]------------
>>  kernel BUG at mm/page_table_check.c:82!
>>  Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>>  Dumping ftrace buffer:
>>     (ftrace buffer empty)
>>  Modules linked in:
>>  CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750
>>  Hardware name: linux,dummy-virt (DT)
>>  pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>  pc : page_table_check_clear.isra.0+0x258/0x3f0
>>  lr : page_table_check_clear.isra.0+0x240/0x3f0
>> [...]
>>  Call trace:
>>   page_table_check_clear.isra.0+0x258/0x3f0
>>   __page_table_check_pmd_clear+0xbc/0x108
>>   pmdp_collapse_flush+0xb0/0x160
>>   collapse_huge_page+0xa08/0x1080
>>   hpage_collapse_scan_pmd+0xf30/0x1590
>>   khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8
>>   khugepaged+0x338/0x518
>>   kthread+0x278/0x2f8
>>   ret_from_fork+0x10/0x20
>> [...]
>>
>> Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it
>> decrease file_map_count for a non-leaf pmd comes from collapse_huge_page().
>> and so trigger BUG_ON() unexpectedly.
> Could you please provide the pmd_val() on the pmd entry, that triggers this
> BUG_ON() here ? Only additional thing pmd_leaf() ensures, is that the entry
> is not a table one.
>
> #define pmd_leaf(pmd)           (pmd_present(pmd) && !pmd_table(pmd))
>
> collapse_huge_page() pmd is non-leaf because it has table bit on ?
The pmd_val is 0x80000004c367003. It is indeed a table entry. collapse_huge_page()
will replace page table of page granularity with block granularity. Before this replace,
it will call pmdp_collapse_flush() to clear the table pmd. In this function, the table pmd
do the check unexpectdly and trigger the BUG_ON().

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 90ab721a12a8..a5c2380bac4d 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -221,6 +221,7 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
 
        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
        VM_BUG_ON(pmd_trans_huge(*pmdp));
+       pr_err("pmd_val is 0x%lx\n", pmd_val(*pmdp));
        pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
 
        /* collapse entails shooting down ptes not pmd */

Thanks,
Liu Shixin
.

>
>> Fix this problem by using pmd_leaf() insteal of pmd_present() in
>> pmd_user_accessible_page(). Moreover, use pud_leaf() for
>> pud_user_accessible_page() too.
>>
>> Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
>> Reported-by: Denys Vlasenko <dvlasenk@redhat.com>
>> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
>> ---
>>  arch/arm64/include/asm/pgtable.h | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index 71a1af42f0e8..edf6625ce965 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -863,12 +863,12 @@ static inline bool pte_user_accessible_page(pte_t pte)
>>  
>>  static inline bool pmd_user_accessible_page(pmd_t pmd)
>>  {
>> -	return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
>> +	return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
>>  }
>>  
>>  static inline bool pud_user_accessible_page(pud_t pud)
>>  {
>> -	return pud_present(pud) && pud_user(pud);
>> +	return pud_leaf(pud) && pud_user(pud);
>>  }
>>  #endif
>>  
> .
>
Denys Vlasenko Nov. 21, 2022, 3:57 p.m. UTC | #5 
On 11/16/22 09:38, Liu Shixin wrote:
> The page table check trigger BUG_ON() unexpectedly when collapse hugepage:
> 
>   ------------[ cut here ]------------
>   kernel BUG at mm/page_table_check.c:82!
>   Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>   Dumping ftrace buffer:
>      (ftrace buffer empty)
>   Modules linked in:
>   CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750
>   Hardware name: linux,dummy-virt (DT)
>   pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>   pc : page_table_check_clear.isra.0+0x258/0x3f0
>   lr : page_table_check_clear.isra.0+0x240/0x3f0
> [...]
>   Call trace:
>    page_table_check_clear.isra.0+0x258/0x3f0
>    __page_table_check_pmd_clear+0xbc/0x108
>    pmdp_collapse_flush+0xb0/0x160
>    collapse_huge_page+0xa08/0x1080
>    hpage_collapse_scan_pmd+0xf30/0x1590
>    khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8
>    khugepaged+0x338/0x518
>    kthread+0x278/0x2f8
>    ret_from_fork+0x10/0x20
> [...]
> 
> Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it
> decrease file_map_count for a non-leaf pmd comes from collapse_huge_page().
> and so trigger BUG_ON() unexpectedly.
> 
> Fix this problem by using pmd_leaf() insteal of pmd_present() in
> pmd_user_accessible_page(). Moreover, use pud_leaf() for
> pud_user_accessible_page() too.
> 
> Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
> Reported-by: Denys Vlasenko <dvlasenk@redhat.com>
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>


Tested on 6.0.6 kernel, no oopses anymore.
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 71a1af42f0e8..edf6625ce965 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -863,12 +863,12 @@  static inline bool pte_user_accessible_page(pte_t pte)
 
 static inline bool pmd_user_accessible_page(pmd_t pmd)
 {
-	return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
+	return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
 }
 
 static inline bool pud_user_accessible_page(pud_t pud)
 {
-	return pud_present(pud) && pud_user(pud);
+	return pud_leaf(pud) && pud_user(pud);
 }
 #endif