diff options
author | Christophe Leroy <christophe.leroy@c-s.fr> | 2017-07-12 17:03:42 +0200 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2017-08-15 22:55:58 +1000 |
commit | ca8afd4046255ac046f8229d5159c6d213e37b22 (patch) | |
tree | d0a7b4617f6dc324d0c4ed42a2270a1995bdb2c8 /arch/powerpc/mm | |
parent | 4cfac2f9c7f116af8516d0b3d0e7383189eca376 (diff) | |
download | linux-stable-ca8afd4046255ac046f8229d5159c6d213e37b22.tar.gz linux-stable-ca8afd4046255ac046f8229d5159c6d213e37b22.tar.bz2 linux-stable-ca8afd4046255ac046f8229d5159c6d213e37b22.zip |
powerpc/hugetlb: fix page rights verification in gup_hugepte()
gup_hugepte() checks if pages are present and readable, and
when 'write' is set, also checks if the pages are writable.
Initially this was done by checking if _PAGE_PRESENT and
_PAGE_READ were set. In addition, _PAGE_WRITE was verified for write
accesses.
The problem is that we have to handle the three following cases:
1/ The target defines __PAGE_READ and __PAGE_WRITE
2/ The target defines __PAGE_RW
3/ The target defines __PAGE_RO
In case 1/, this is obvious
In case 2/, __PAGE_READ is defined as 0 and __PAGE_WRITE as __PAGE_RW
so it works as well.
But in case 3, __PAGE_RW is defined as 0, which means __PAGE_WRITE is 0
and then the test returns true (page writable) in all cases.
A first correction was attempted in commit 6b8cb66a6a7cc ("powerpc: Fix
usage of _PAGE_RO in hugepage"), but that fix is wrong:
instead of checking that the page is writable when write is requested,
it checks that the page is NOT writable when write is NOT requested.
This patch adds a new pte_read() helper to check whether a page is
readable or not. This avoids handling all possible cases in
gup_hugepte().
Then gup_hugepte() is modified to use pte_present(), pte_read()
and pte_write() instead of the raw flags.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r-- | arch/powerpc/mm/hugetlbpage.c | 15 |
1 files changed, 3 insertions, 12 deletions
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c index e1bf5ca397fe..1226932579a0 100644 --- a/arch/powerpc/mm/hugetlbpage.c +++ b/arch/powerpc/mm/hugetlbpage.c @@ -977,7 +977,6 @@ EXPORT_SYMBOL_GPL(__find_linux_pte_or_hugepte); int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) { - unsigned long mask; unsigned long pte_end; struct page *head, *page; pte_t pte; @@ -988,18 +987,10 @@ int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, end = pte_end; pte = READ_ONCE(*ptep); - mask = _PAGE_PRESENT | _PAGE_READ; - - /* - * On some CPUs like the 8xx, _PAGE_RW hence _PAGE_WRITE is defined - * as 0 and _PAGE_RO has to be set when a page is not writable - */ - if (write) - mask |= _PAGE_WRITE; - else - mask |= _PAGE_RO; - if ((pte_val(pte) & mask) != mask) + if (!pte_present(pte) || !pte_read(pte)) + return 0; + if (write && !pte_write(pte)) return 0; /* hugepages are never "special" */ |