Le 21/08/2018 à 16:25, Aneesh Kumar K.V a écrit :
Christophe Leroy <christophe.leroy@xxxxxx> 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/87lgcusc6z.fsf@xxxxxxxxxxxxxxxxxx/T/#u
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
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: stable@xxxxxxxxxxxxxxx # v4.15+
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
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
