Messages in this thread |  | | From | Michael Ellerman <> | Subject | Re: powerpc/hugetlb: fix page rights verification in gup_hugepte() | Date | Wed, 16 Aug 2017 22:29:47 +1000 (AEST) |
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On Wed, 2017-07-12 at 15:03:42 UTC, Christophe Leroy wrote: > 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>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/ca8afd4046255ac046f8229d5159c6
cheers
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