Commit 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper
for other platforms") replaced generic pte_access_permitted() by an
arch specific one.
The generic one is defined as
(pte_present(pte) && (!(write) || pte_write(pte)))
The arch specific one is open coded checking that _PAGE_USER and
_PAGE_WRITE (_PAGE_RW) flags are set, but lacking to check that
_PAGE_RO and _PAGE_PRIVILEGED are unset, leading to a useless test
on targets like the 8xx which defines _PAGE_RW and _PAGE_USER as 0.
Commit 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted
for hugetlb access check") replaced some tests performed with
pte helpers by a call to pte_access_permitted(), leading to the same
issue.
This patch rewrites powerpc/nohash pte_access_permitted()
using pte helpers.
Fixes: 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper for other platforms")
Fixes: 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted for hugetlb access check")
Cc: [email protected] # v4.15+
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/include/asm/nohash/pgtable.h | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 2160be2e4339..b321c82b3624 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -51,17 +51,14 @@ static inline int pte_present(pte_t pte)
#define pte_access_permitted pte_access_permitted
static inline bool pte_access_permitted(pte_t pte, bool write)
{
- unsigned long pteval = pte_val(pte);
/*
* A read-only access is controlled by _PAGE_USER bit.
* We have _PAGE_READ set for WRITE and EXECUTE
*/
- unsigned long need_pte_bits = _PAGE_PRESENT | _PAGE_USER;
-
- if (write)
- need_pte_bits |= _PAGE_WRITE;
+ if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
+ return false;
- if ((pteval & need_pte_bits) != need_pte_bits)
+ if (write && !pte_write(pte))
return false;
return true;
--
2.13.3
Christophe Leroy <[email protected]> writes:
> Commit 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper
> for other platforms") replaced generic pte_access_permitted() by an
> arch specific one.
>
> The generic one is defined as
> (pte_present(pte) && (!(write) || pte_write(pte)))
>
> The arch specific one is open coded checking that _PAGE_USER and
> _PAGE_WRITE (_PAGE_RW) flags are set, but lacking to check that
> _PAGE_RO and _PAGE_PRIVILEGED are unset, leading to a useless test
> on targets like the 8xx which defines _PAGE_RW and _PAGE_USER as 0.
>
> Commit 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted
> for hugetlb access check") replaced some tests performed with
> pte helpers by a call to pte_access_permitted(), leading to the same
> issue.
>
> This patch rewrites powerpc/nohash pte_access_permitted()
> using pte helpers.
>
Thanks for fixing this. I should have used the helper instead of
opencoding it on nohash platforms. This is another reason why I was also
suggesting we should avoid consolidating pte accessors across platforms
and user accessors instead of opencoding.
https://lore.kernel.org/lkml/[email protected]/T/#u
Reviewed-by: Aneesh Kumar K.V <[email protected]>
> Fixes: 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper for other platforms")
> Fixes: 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted for hugetlb access check")
> Cc: [email protected] # v4.15+
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> arch/powerpc/include/asm/nohash/pgtable.h | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
> index 2160be2e4339..b321c82b3624 100644
> --- a/arch/powerpc/include/asm/nohash/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/pgtable.h
> @@ -51,17 +51,14 @@ static inline int pte_present(pte_t pte)
> #define pte_access_permitted pte_access_permitted
> static inline bool pte_access_permitted(pte_t pte, bool write)
> {
> - unsigned long pteval = pte_val(pte);
> /*
> * A read-only access is controlled by _PAGE_USER bit.
> * We have _PAGE_READ set for WRITE and EXECUTE
> */
> - unsigned long need_pte_bits = _PAGE_PRESENT | _PAGE_USER;
> -
> - if (write)
> - need_pte_bits |= _PAGE_WRITE;
> + if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
> + return false;
>
> - if ((pteval & need_pte_bits) != need_pte_bits)
> + if (write && !pte_write(pte))
> return false;
>
> return true;
> --
> 2.13.3
Le 21/08/2018 à 16:25, Aneesh Kumar K.V a écrit :
> Christophe Leroy <[email protected]> writes:
>
>> Commit 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper
>> for other platforms") replaced generic pte_access_permitted() by an
>> arch specific one.
>>
>> The generic one is defined as
>> (pte_present(pte) && (!(write) || pte_write(pte)))
>>
>> The arch specific one is open coded checking that _PAGE_USER and
>> _PAGE_WRITE (_PAGE_RW) flags are set, but lacking to check that
>> _PAGE_RO and _PAGE_PRIVILEGED are unset, leading to a useless test
>> on targets like the 8xx which defines _PAGE_RW and _PAGE_USER as 0.
>>
>> Commit 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted
>> for hugetlb access check") replaced some tests performed with
>> pte helpers by a call to pte_access_permitted(), leading to the same
>> issue.
>>
>> This patch rewrites powerpc/nohash pte_access_permitted()
>> using pte helpers.
>>
>
> Thanks for fixing this. I should have used the helper instead of
> opencoding it on nohash platforms. This is another reason why I was also
> suggesting we should avoid consolidating pte accessors across platforms
> and user accessors instead of opencoding.
I fully agree. I have opened a topic for that at
https://github.com/linuxppc/linux/issues/177
Christophe
>
> https://lore.kernel.org/lkml/[email protected]/T/#u
>
> Reviewed-by: Aneesh Kumar K.V <[email protected]>
>
>> Fixes: 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper for other platforms")
>> Fixes: 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted for hugetlb access check")
>> Cc: [email protected] # v4.15+
>> Signed-off-by: Christophe Leroy <[email protected]>
>> ---
>> arch/powerpc/include/asm/nohash/pgtable.h | 9 +++------
>> 1 file changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
>> index 2160be2e4339..b321c82b3624 100644
>> --- a/arch/powerpc/include/asm/nohash/pgtable.h
>> +++ b/arch/powerpc/include/asm/nohash/pgtable.h
>> @@ -51,17 +51,14 @@ static inline int pte_present(pte_t pte)
>> #define pte_access_permitted pte_access_permitted
>> static inline bool pte_access_permitted(pte_t pte, bool write)
>> {
>> - unsigned long pteval = pte_val(pte);
>> /*
>> * A read-only access is controlled by _PAGE_USER bit.
>> * We have _PAGE_READ set for WRITE and EXECUTE
>> */
>> - unsigned long need_pte_bits = _PAGE_PRESENT | _PAGE_USER;
>> -
>> - if (write)
>> - need_pte_bits |= _PAGE_WRITE;
>> + if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
>> + return false;
>>
>> - if ((pteval & need_pte_bits) != need_pte_bits)
>> + if (write && !pte_write(pte))
>> return false;
>>
>> return true;
>> --
>> 2.13.3
On Tue, 2018-08-21 at 13:03:23 UTC, Christophe Leroy wrote:
> Commit 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper
> for other platforms") replaced generic pte_access_permitted() by an
> arch specific one.
>
> The generic one is defined as
> (pte_present(pte) && (!(write) || pte_write(pte)))
>
> The arch specific one is open coded checking that _PAGE_USER and
> _PAGE_WRITE (_PAGE_RW) flags are set, but lacking to check that
> _PAGE_RO and _PAGE_PRIVILEGED are unset, leading to a useless test
> on targets like the 8xx which defines _PAGE_RW and _PAGE_USER as 0.
>
> Commit 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted
> for hugetlb access check") replaced some tests performed with
> pte helpers by a call to pte_access_permitted(), leading to the same
> issue.
>
> This patch rewrites powerpc/nohash pte_access_permitted()
> using pte helpers.
>
> Fixes: 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper for other platforms")
> Fixes: 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted for hugetlb access check")
> Cc: [email protected] # v4.15+
> Signed-off-by: Christophe Leroy <[email protected]>
> Reviewed-by: Aneesh Kumar K.V <[email protected]>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/810e9f86f36f59f1d6f6710220c49a
cheers