4.14-stable review patch. If anyone has any objections, please let me know.
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From: Catalin Marinas catalin.marinas@arm.com
commit 6218f96c58dbf44a06aeaf767aab1f54fc397838 upstream.
The generic pte_access_permitted() implementation only checks for pte_present() (together with the write permission where applicable). However, for both kernel ptes and PROT_NONE mappings pte_present() also returns true on arm64 even though such mappings are not user accessible. Additionally, arm64 now supports execute-only user permission (PROT_EXEC) which is implemented by clearing the PTE_USER bit.
With this patch the arm64 implementation of pte_access_permitted() checks for the PTE_VALID and PTE_USER bits together with writable access if applicable.
Reported-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/include/asm/pgtable.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
--- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -98,6 +98,8 @@ extern unsigned long empty_zero_page[PAG ((pte_val(pte) & (PTE_VALID | PTE_USER | PTE_UXN)) == (PTE_VALID | PTE_UXN)) #define pte_valid_young(pte) \ ((pte_val(pte) & (PTE_VALID | PTE_AF)) == (PTE_VALID | PTE_AF)) +#define pte_valid_user(pte) \ + ((pte_val(pte) & (PTE_VALID | PTE_USER)) == (PTE_VALID | PTE_USER))
/* * Could the pte be present in the TLB? We must check mm_tlb_flush_pending @@ -107,6 +109,18 @@ extern unsigned long empty_zero_page[PAG #define pte_accessible(mm, pte) \ (mm_tlb_flush_pending(mm) ? pte_present(pte) : pte_valid_young(pte))
+/* + * p??_access_permitted() is true for valid user mappings (subject to the + * write permission check) other than user execute-only which do not have the + * PTE_USER bit set. PROT_NONE mappings do not have the PTE_VALID bit set. + */ +#define pte_access_permitted(pte, write) \ + (pte_valid_user(pte) && (!(write) || pte_write(pte))) +#define pmd_access_permitted(pmd, write) \ + (pte_access_permitted(pmd_pte(pmd), (write))) +#define pud_access_permitted(pud, write) \ + (pte_access_permitted(pud_pte(pud), (write))) + static inline pte_t clear_pte_bit(pte_t pte, pgprot_t prot) { pte_val(pte) &= ~pgprot_val(prot);