* Re: [PATCH] arm64: mm: fix pmd_leaf()
@ 2022-04-04 9:19 ` Will Deacon
0 siblings, 0 replies; 12+ messages in thread
From: Will Deacon @ 2022-04-04 9:19 UTC (permalink / raw)
To: Muchun Song
Cc: catalin.marinas, akpm, anshuman.khandual, aneesh.kumar,
steven.price, lengxujun2007, arnd, linux-arm-kernel,
linux-kernel, smuchun, duanxiongchun, Qian Cai
On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
> The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
> the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
> caused by this was reported by Qian Cai.
>
> Link: https://patchwork.kernel.org/comment/24798260/ [1]
> Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
> Reported-by: Qian Cai <quic_qiancai@quicinc.com>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> arch/arm64/include/asm/pgtable.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 94e147e5456c..09eaae46a19b 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> PMD_TYPE_TABLE)
> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
> PMD_TYPE_SECT)
> -#define pmd_leaf(pmd) pmd_sect(pmd)
> +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
> #define pmd_bad(pmd) (!pmd_table(pmd))
>
> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
A bunch of the users of pmd_leaf() already check pmd_present() -- is it
documented that we need to handle this check inside the macro? afaict x86
doesn't do this either.
Will
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^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] arm64: mm: fix pmd_leaf()
2022-04-04 9:19 ` Will Deacon
@ 2022-04-04 10:51 ` Steven Price
-1 siblings, 0 replies; 12+ messages in thread
From: Steven Price @ 2022-04-04 10:51 UTC (permalink / raw)
To: Will Deacon, Muchun Song
Cc: catalin.marinas, akpm, anshuman.khandual, aneesh.kumar,
lengxujun2007, arnd, linux-arm-kernel, linux-kernel, smuchun,
duanxiongchun, Qian Cai
On 04/04/2022 10:19, Will Deacon wrote:
> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
>> The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
>> the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
>> caused by this was reported by Qian Cai.
>>
>> Link: https://patchwork.kernel.org/comment/24798260/ [1]
>> Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
>> Reported-by: Qian Cai <quic_qiancai@quicinc.com>
>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>> ---
>> arch/arm64/include/asm/pgtable.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index 94e147e5456c..09eaae46a19b 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>> PMD_TYPE_TABLE)
>> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
>> PMD_TYPE_SECT)
>> -#define pmd_leaf(pmd) pmd_sect(pmd)
>> +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
>> #define pmd_bad(pmd) (!pmd_table(pmd))
>>
>> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
>
> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
> documented that we need to handle this check inside the macro? afaict x86
> doesn't do this either.
The documentation is with the fallback implementations that always
return 0:
> /*
> * p?d_leaf() - true if this entry is a final mapping to a physical address.
> * This differs from p?d_huge() by the fact that they are always available (if
> * the architecture supports large pages at the appropriate level) even
> * if CONFIG_HUGETLB_PAGE is not defined.
> * Only meaningful when called on a valid entry.
> */
I guess the term "valid entry" is a bit vague but my intention was that
meant p?d_present().
I have to admit I hadn't considered PROT_NONE mappings before.
Steve
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] arm64: mm: fix pmd_leaf()
@ 2022-04-04 10:51 ` Steven Price
0 siblings, 0 replies; 12+ messages in thread
From: Steven Price @ 2022-04-04 10:51 UTC (permalink / raw)
To: Will Deacon, Muchun Song
Cc: catalin.marinas, akpm, anshuman.khandual, aneesh.kumar,
lengxujun2007, arnd, linux-arm-kernel, linux-kernel, smuchun,
duanxiongchun, Qian Cai
On 04/04/2022 10:19, Will Deacon wrote:
> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
>> The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
>> the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
>> caused by this was reported by Qian Cai.
>>
>> Link: https://patchwork.kernel.org/comment/24798260/ [1]
>> Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
>> Reported-by: Qian Cai <quic_qiancai@quicinc.com>
>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>> ---
>> arch/arm64/include/asm/pgtable.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index 94e147e5456c..09eaae46a19b 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>> PMD_TYPE_TABLE)
>> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
>> PMD_TYPE_SECT)
>> -#define pmd_leaf(pmd) pmd_sect(pmd)
>> +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
>> #define pmd_bad(pmd) (!pmd_table(pmd))
>>
>> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
>
> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
> documented that we need to handle this check inside the macro? afaict x86
> doesn't do this either.
The documentation is with the fallback implementations that always
return 0:
> /*
> * p?d_leaf() - true if this entry is a final mapping to a physical address.
> * This differs from p?d_huge() by the fact that they are always available (if
> * the architecture supports large pages at the appropriate level) even
> * if CONFIG_HUGETLB_PAGE is not defined.
> * Only meaningful when called on a valid entry.
> */
I guess the term "valid entry" is a bit vague but my intention was that
meant p?d_present().
I have to admit I hadn't considered PROT_NONE mappings before.
Steve
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] arm64: mm: fix pmd_leaf()
2022-04-04 9:19 ` Will Deacon
@ 2022-04-04 11:40 ` Muchun Song
-1 siblings, 0 replies; 12+ messages in thread
From: Muchun Song @ 2022-04-04 11:40 UTC (permalink / raw)
To: Will Deacon
Cc: Catalin Marinas, Andrew Morton, Anshuman Khandual,
Aneesh Kumar K . V, steven.price, lengxujun2007, Arnd Bergmann,
LAK, LKML, Muchun Song, Xiongchun duan, Qian Cai
On Mon, Apr 4, 2022 at 5:20 PM Will Deacon <will@kernel.org> wrote:
>
> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
> > The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
> > the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
> > caused by this was reported by Qian Cai.
> >
> > Link: https://patchwork.kernel.org/comment/24798260/ [1]
> > Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
> > Reported-by: Qian Cai <quic_qiancai@quicinc.com>
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > ---
> > arch/arm64/include/asm/pgtable.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> > index 94e147e5456c..09eaae46a19b 100644
> > --- a/arch/arm64/include/asm/pgtable.h
> > +++ b/arch/arm64/include/asm/pgtable.h
> > @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> > PMD_TYPE_TABLE)
> > #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
> > PMD_TYPE_SECT)
> > -#define pmd_leaf(pmd) pmd_sect(pmd)
> > +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
> > #define pmd_bad(pmd) (!pmd_table(pmd))
> >
> > #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
>
> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
> documented that we need to handle this check inside the macro? afaict x86
> doesn't do this either.
>
arm64 is different from x86 here. pmd_leaf() could return true for
the none pmd without pmd_present() check, the check of
pmd_present() aims to exclude the pmd_none() case. However,
it could work properly on x86 without pmd_present() or pmd_none().
So we don't see pmd_present() or pmd_none() check in pmd_leaf().
For this reason, I think this check is necessary.
BTW, there are some users of pmd_leaf() (e.g. apply_to_pmd_range,
walk_pmd_range, ptdump_pmd_entry) which do not check pmd_present()
or pmd_none() before the call of pmd_leaf(). So it is also necessary
to add the check.
Thanks.
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] arm64: mm: fix pmd_leaf()
@ 2022-04-04 11:40 ` Muchun Song
0 siblings, 0 replies; 12+ messages in thread
From: Muchun Song @ 2022-04-04 11:40 UTC (permalink / raw)
To: Will Deacon
Cc: Catalin Marinas, Andrew Morton, Anshuman Khandual,
Aneesh Kumar K . V, steven.price, lengxujun2007, Arnd Bergmann,
LAK, LKML, Muchun Song, Xiongchun duan, Qian Cai
On Mon, Apr 4, 2022 at 5:20 PM Will Deacon <will@kernel.org> wrote:
>
> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
> > The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
> > the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
> > caused by this was reported by Qian Cai.
> >
> > Link: https://patchwork.kernel.org/comment/24798260/ [1]
> > Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
> > Reported-by: Qian Cai <quic_qiancai@quicinc.com>
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > ---
> > arch/arm64/include/asm/pgtable.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> > index 94e147e5456c..09eaae46a19b 100644
> > --- a/arch/arm64/include/asm/pgtable.h
> > +++ b/arch/arm64/include/asm/pgtable.h
> > @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> > PMD_TYPE_TABLE)
> > #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
> > PMD_TYPE_SECT)
> > -#define pmd_leaf(pmd) pmd_sect(pmd)
> > +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
> > #define pmd_bad(pmd) (!pmd_table(pmd))
> >
> > #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
>
> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
> documented that we need to handle this check inside the macro? afaict x86
> doesn't do this either.
>
arm64 is different from x86 here. pmd_leaf() could return true for
the none pmd without pmd_present() check, the check of
pmd_present() aims to exclude the pmd_none() case. However,
it could work properly on x86 without pmd_present() or pmd_none().
So we don't see pmd_present() or pmd_none() check in pmd_leaf().
For this reason, I think this check is necessary.
BTW, there are some users of pmd_leaf() (e.g. apply_to_pmd_range,
walk_pmd_range, ptdump_pmd_entry) which do not check pmd_present()
or pmd_none() before the call of pmd_leaf(). So it is also necessary
to add the check.
Thanks.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] arm64: mm: fix pmd_leaf()
2022-04-04 11:40 ` Muchun Song
@ 2022-04-04 14:10 ` Aneesh Kumar K V
-1 siblings, 0 replies; 12+ messages in thread
From: Aneesh Kumar K V @ 2022-04-04 14:10 UTC (permalink / raw)
To: Muchun Song, Will Deacon
Cc: Catalin Marinas, Andrew Morton, Anshuman Khandual, steven.price,
lengxujun2007, Arnd Bergmann, LAK, LKML, Muchun Song,
Xiongchun duan, Qian Cai
On 4/4/22 5:10 PM, Muchun Song wrote:
> On Mon, Apr 4, 2022 at 5:20 PM Will Deacon <will@kernel.org> wrote:
>>
>> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
>>> The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
>>> the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
>>> caused by this was reported by Qian Cai.
>>>
>>> Link: https://patchwork.kernel.org/comment/24798260/ [1]
>>> Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
>>> Reported-by: Qian Cai <quic_qiancai@quicinc.com>
>>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>>> ---
>>> arch/arm64/include/asm/pgtable.h | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>>> index 94e147e5456c..09eaae46a19b 100644
>>> --- a/arch/arm64/include/asm/pgtable.h
>>> +++ b/arch/arm64/include/asm/pgtable.h
>>> @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>>> PMD_TYPE_TABLE)
>>> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
>>> PMD_TYPE_SECT)
>>> -#define pmd_leaf(pmd) pmd_sect(pmd)
>>> +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
>>> #define pmd_bad(pmd) (!pmd_table(pmd))
>>>
>>> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
>>
>> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
>> documented that we need to handle this check inside the macro? afaict x86
>> doesn't do this either.
ppc64 also doesn't do a pmd_present check.
>>
>
> arm64 is different from x86 here. pmd_leaf() could return true for
> the none pmd without pmd_present() check, the check of
> pmd_present() aims to exclude the pmd_none() case. However,
> it could work properly on x86 without pmd_present() or pmd_none().
> So we don't see pmd_present() or pmd_none() check in pmd_leaf().
> For this reason, I think this check is necessary.
>
> BTW, there are some users of pmd_leaf() (e.g. apply_to_pmd_range,
> walk_pmd_range, ptdump_pmd_entry) which do not check pmd_present()
> or pmd_none() before the call of pmd_leaf(). So it is also necessary
> to add the check.
>
I would expect pmd_leaf check to return true, if the said pmd page table
entry can point to a leaf page table entry which can also be a not
present page table entry?
-aneesh
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] arm64: mm: fix pmd_leaf()
@ 2022-04-04 14:10 ` Aneesh Kumar K V
0 siblings, 0 replies; 12+ messages in thread
From: Aneesh Kumar K V @ 2022-04-04 14:10 UTC (permalink / raw)
To: Muchun Song, Will Deacon
Cc: Catalin Marinas, Andrew Morton, Anshuman Khandual, steven.price,
lengxujun2007, Arnd Bergmann, LAK, LKML, Muchun Song,
Xiongchun duan, Qian Cai
On 4/4/22 5:10 PM, Muchun Song wrote:
> On Mon, Apr 4, 2022 at 5:20 PM Will Deacon <will@kernel.org> wrote:
>>
>> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
>>> The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
>>> the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
>>> caused by this was reported by Qian Cai.
>>>
>>> Link: https://patchwork.kernel.org/comment/24798260/ [1]
>>> Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
>>> Reported-by: Qian Cai <quic_qiancai@quicinc.com>
>>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>>> ---
>>> arch/arm64/include/asm/pgtable.h | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>>> index 94e147e5456c..09eaae46a19b 100644
>>> --- a/arch/arm64/include/asm/pgtable.h
>>> +++ b/arch/arm64/include/asm/pgtable.h
>>> @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>>> PMD_TYPE_TABLE)
>>> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
>>> PMD_TYPE_SECT)
>>> -#define pmd_leaf(pmd) pmd_sect(pmd)
>>> +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
>>> #define pmd_bad(pmd) (!pmd_table(pmd))
>>>
>>> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
>>
>> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
>> documented that we need to handle this check inside the macro? afaict x86
>> doesn't do this either.
ppc64 also doesn't do a pmd_present check.
>>
>
> arm64 is different from x86 here. pmd_leaf() could return true for
> the none pmd without pmd_present() check, the check of
> pmd_present() aims to exclude the pmd_none() case. However,
> it could work properly on x86 without pmd_present() or pmd_none().
> So we don't see pmd_present() or pmd_none() check in pmd_leaf().
> For this reason, I think this check is necessary.
>
> BTW, there are some users of pmd_leaf() (e.g. apply_to_pmd_range,
> walk_pmd_range, ptdump_pmd_entry) which do not check pmd_present()
> or pmd_none() before the call of pmd_leaf(). So it is also necessary
> to add the check.
>
I would expect pmd_leaf check to return true, if the said pmd page table
entry can point to a leaf page table entry which can also be a not
present page table entry?
-aneesh
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] arm64: mm: fix pmd_leaf()
2022-04-04 14:10 ` Aneesh Kumar K V
@ 2022-04-04 15:24 ` Muchun Song
-1 siblings, 0 replies; 12+ messages in thread
From: Muchun Song @ 2022-04-04 15:24 UTC (permalink / raw)
To: Aneesh Kumar K V
Cc: Will Deacon, Catalin Marinas, Andrew Morton, Anshuman Khandual,
steven.price, lengxujun2007, Arnd Bergmann, LAK, LKML,
Muchun Song, Xiongchun duan, Qian Cai
On Mon, Apr 4, 2022 at 10:10 PM Aneesh Kumar K V
<aneesh.kumar@linux.ibm.com> wrote:
>
> On 4/4/22 5:10 PM, Muchun Song wrote:
> > On Mon, Apr 4, 2022 at 5:20 PM Will Deacon <will@kernel.org> wrote:
> >>
> >> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
> >>> The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
> >>> the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
> >>> caused by this was reported by Qian Cai.
> >>>
> >>> Link: https://patchwork.kernel.org/comment/24798260/ [1]
> >>> Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
> >>> Reported-by: Qian Cai <quic_qiancai@quicinc.com>
> >>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> >>> ---
> >>> arch/arm64/include/asm/pgtable.h | 2 +-
> >>> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> >>> index 94e147e5456c..09eaae46a19b 100644
> >>> --- a/arch/arm64/include/asm/pgtable.h
> >>> +++ b/arch/arm64/include/asm/pgtable.h
> >>> @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> >>> PMD_TYPE_TABLE)
> >>> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
> >>> PMD_TYPE_SECT)
> >>> -#define pmd_leaf(pmd) pmd_sect(pmd)
> >>> +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
> >>> #define pmd_bad(pmd) (!pmd_table(pmd))
> >>>
> >>> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
> >>
> >> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
> >> documented that we need to handle this check inside the macro? afaict x86
> >> doesn't do this either.
>
>
> ppc64 also doesn't do a pmd_present check.
>
> >>
> >
> > arm64 is different from x86 here. pmd_leaf() could return true for
> > the none pmd without pmd_present() check, the check of
> > pmd_present() aims to exclude the pmd_none() case. However,
> > it could work properly on x86 without pmd_present() or pmd_none().
> > So we don't see pmd_present() or pmd_none() check in pmd_leaf().
> > For this reason, I think this check is necessary.
> >
> > BTW, there are some users of pmd_leaf() (e.g. apply_to_pmd_range,
> > walk_pmd_range, ptdump_pmd_entry) which do not check pmd_present()
> > or pmd_none() before the call of pmd_leaf(). So it is also necessary
> > to add the check.
> >
>
>
> I would expect pmd_leaf check to return true, if the said pmd page table
> entry can point to a leaf page table entry which can also be a not
> present page table entry?
>
All right. In order to exclude the pmd_none() case. How about
the following code?
#define pmd_leaf(pmd) (pmd_val(pmd) && !(pmd_val(pmd) &
PMD_TABLE_BIT))
Thanks.
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] arm64: mm: fix pmd_leaf()
@ 2022-04-04 15:24 ` Muchun Song
0 siblings, 0 replies; 12+ messages in thread
From: Muchun Song @ 2022-04-04 15:24 UTC (permalink / raw)
To: Aneesh Kumar K V
Cc: Will Deacon, Catalin Marinas, Andrew Morton, Anshuman Khandual,
steven.price, lengxujun2007, Arnd Bergmann, LAK, LKML,
Muchun Song, Xiongchun duan, Qian Cai
On Mon, Apr 4, 2022 at 10:10 PM Aneesh Kumar K V
<aneesh.kumar@linux.ibm.com> wrote:
>
> On 4/4/22 5:10 PM, Muchun Song wrote:
> > On Mon, Apr 4, 2022 at 5:20 PM Will Deacon <will@kernel.org> wrote:
> >>
> >> On Sun, Apr 03, 2022 at 10:49:28AM +0800, Muchun Song wrote:
> >>> The pmd_leaf() is used to test a leaf mapped PMD, however, it misses
> >>> the PROT_NONE mapped PMD on arm64. Fix it. A real world issue [1]
> >>> caused by this was reported by Qian Cai.
> >>>
> >>> Link: https://patchwork.kernel.org/comment/24798260/ [1]
> >>> Fixes: 8aa82df3c123 ("arm64: mm: add p?d_leaf() definitions")
> >>> Reported-by: Qian Cai <quic_qiancai@quicinc.com>
> >>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> >>> ---
> >>> arch/arm64/include/asm/pgtable.h | 2 +-
> >>> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> >>> index 94e147e5456c..09eaae46a19b 100644
> >>> --- a/arch/arm64/include/asm/pgtable.h
> >>> +++ b/arch/arm64/include/asm/pgtable.h
> >>> @@ -535,7 +535,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> >>> PMD_TYPE_TABLE)
> >>> #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
> >>> PMD_TYPE_SECT)
> >>> -#define pmd_leaf(pmd) pmd_sect(pmd)
> >>> +#define pmd_leaf(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
> >>> #define pmd_bad(pmd) (!pmd_table(pmd))
> >>>
> >>> #define pmd_leaf_size(pmd) (pmd_cont(pmd) ? CONT_PMD_SIZE : PMD_SIZE)
> >>
> >> A bunch of the users of pmd_leaf() already check pmd_present() -- is it
> >> documented that we need to handle this check inside the macro? afaict x86
> >> doesn't do this either.
>
>
> ppc64 also doesn't do a pmd_present check.
>
> >>
> >
> > arm64 is different from x86 here. pmd_leaf() could return true for
> > the none pmd without pmd_present() check, the check of
> > pmd_present() aims to exclude the pmd_none() case. However,
> > it could work properly on x86 without pmd_present() or pmd_none().
> > So we don't see pmd_present() or pmd_none() check in pmd_leaf().
> > For this reason, I think this check is necessary.
> >
> > BTW, there are some users of pmd_leaf() (e.g. apply_to_pmd_range,
> > walk_pmd_range, ptdump_pmd_entry) which do not check pmd_present()
> > or pmd_none() before the call of pmd_leaf(). So it is also necessary
> > to add the check.
> >
>
>
> I would expect pmd_leaf check to return true, if the said pmd page table
> entry can point to a leaf page table entry which can also be a not
> present page table entry?
>
All right. In order to exclude the pmd_none() case. How about
the following code?
#define pmd_leaf(pmd) (pmd_val(pmd) && !(pmd_val(pmd) &
PMD_TABLE_BIT))
Thanks.
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^ permalink raw reply [flat|nested] 12+ messages in thread