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s390/mm: properly clear _PAGE_NOEXEC bit when it is not supported
On older HW or under a hypervisor, w/o the instruction-execution-
protection (IEP) facility, and also w/o EDAT-1, a translation-specification
exception may be recognized when bit 55 of a pte is one (_PAGE_NOEXEC).
The current code tries to prevent setting _PAGE_NOEXEC in such cases,
by removing it within set_pte_at(). However, ptep_set_access_flags()
will modify a pte directly, w/o using set_pte_at(). There is at least
one scenario where this can result in an active pte with _PAGE_NOEXEC
set, which would then lead to a panic due to a translation-specification
exception (write to swapped out page):
do_swap_page
pte = mk_pte (with _PAGE_NOEXEC bit)
set_pte_at (will remove _PAGE_NOEXEC bit in page table, but keep it
in local variable pte)
vmf->orig_pte = pte (pte still contains _PAGE_NOEXEC bit)
do_wp_page
wp_page_reuse
entry = vmf->orig_pte (still with _PAGE_NOEXEC bit)
ptep_set_access_flags (writes entry with _PAGE_NOEXEC bit)
Fix this by clearing _PAGE_NOEXEC already in mk_pte_phys(), where the
pgprot value is applied, so that no pte with _PAGE_NOEXEC will ever be
visible, if it is not supported. The check in set_pte_at() can then also
be removed.
Cc: <stable@vger.kernel.org> # 4.11+
Fixes: 57d7f939e7
("s390: add no-execute support")
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
parent
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@ -1161,8 +1161,6 @@ void gmap_pmdp_idte_global(struct mm_struct *mm, unsigned long vmaddr);
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static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
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pte_t *ptep, pte_t entry)
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{
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if (!MACHINE_HAS_NX)
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pte_val(entry) &= ~_PAGE_NOEXEC;
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if (pte_present(entry))
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pte_val(entry) &= ~_PAGE_UNUSED;
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if (mm_has_pgste(mm))
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@ -1179,6 +1177,8 @@ static inline pte_t mk_pte_phys(unsigned long physpage, pgprot_t pgprot)
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{
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pte_t __pte;
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pte_val(__pte) = physpage + pgprot_val(pgprot);
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if (!MACHINE_HAS_NX)
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pte_val(__pte) &= ~_PAGE_NOEXEC;
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return pte_mkyoung(__pte);
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}
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