Le 14/07/2017 à 08:51, Michael Ellerman a écrit :
Currently even with STRICT_KERNEL_RWX we leave the __init text marked
executable after init, which is bad.
Add a hook to mark it NX (no-execute) before we free it, and implement
it for radix and hash.
Note that we use __init_end as the end address, not _einittext,
because overlaps_kernel_text() uses __init_end, because there are
additional executable sections other than .init.text between
__init_begin and __init_end.
Tested on radix and hash with:
0:mon> p $__init_begin
*** 400 exception occurred
Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some
configs")
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
arch/powerpc/include/asm/book3s/64/hash.h | 1 +
arch/powerpc/include/asm/book3s/64/pgtable.h | 7 +++++++
arch/powerpc/include/asm/book3s/64/radix.h | 1 +
arch/powerpc/mm/mem.c | 1 +
arch/powerpc/mm/pgtable-hash64.c | 12 ++++++++++++
arch/powerpc/mm/pgtable-radix.c | 8 ++++++++
arch/powerpc/mm/pgtable_64.c | 8 ++++++++
7 files changed, 38 insertions(+)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h
b/arch/powerpc/include/asm/book3s/64/hash.h
index 0ce513f2926f..36fc7bfe9e11 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -91,6 +91,7 @@ static inline int hash__pgd_bad(pgd_t pgd)
}
#ifdef CONFIG_STRICT_KERNEL_RWX
extern void hash__mark_rodata_ro(void);
+extern void hash__mark_initmem_nx(void);
#endif
extern void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
b/arch/powerpc/include/asm/book3s/64/pgtable.h
index c0737c86a362..3d562b210c65 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1192,5 +1192,12 @@ static inline const int pud_pfn(pud_t pud)
BUILD_BUG();
return 0;
}
+
+#ifdef CONFIG_STRICT_KERNEL_RWX
+void mark_initmem_nx(void);
+#else
+static inline void mark_initmem_nx(void) { }
+#endif
+
Why do we want to limit that to CONFIG_STRICT_KERNEL_RWX ?
Only the kernel text is marked X, even without CONFIG_STRICT_KERNEL_RWX
(at least on PPC32), so I believe we should clear X on init text in any
case, shouldn't we ?
Christophe
#endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ */
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h
b/arch/powerpc/include/asm/book3s/64/radix.h
index 487709ff6875..544440b5aff3 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -118,6 +118,7 @@
#ifdef CONFIG_STRICT_KERNEL_RWX
extern void radix__mark_rodata_ro(void);
+extern void radix__mark_initmem_nx(void);
#endif
static inline unsigned long __radix_pte_update(pte_t *ptep, unsigned long clr,
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 8541f18694a4..46b4e67d2372 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -402,6 +402,7 @@ void __init mem_init(void)
void free_initmem(void)
{
ppc_md.progress = ppc_printk_progress;
+ mark_initmem_nx();
free_initmem_default(POISON_FREE_INITMEM);
}
diff --git a/arch/powerpc/mm/pgtable-hash64.c b/arch/powerpc/mm/pgtable-hash64.c
index 73019c52141f..443a2c66a304 100644
--- a/arch/powerpc/mm/pgtable-hash64.c
+++ b/arch/powerpc/mm/pgtable-hash64.c
@@ -460,4 +460,16 @@ void hash__mark_rodata_ro(void)
WARN_ON(!hash__change_memory_range(start, end, PP_RXXX));
}
+
+void hash__mark_initmem_nx(void)
+{
+ unsigned long start, end, pp;
+
+ start = (unsigned long)__init_begin;
+ end = (unsigned long)__init_end;
+
+ pp = htab_convert_pte_flags(pgprot_val(PAGE_KERNEL));
+
+ WARN_ON(!hash__change_memory_range(start, end, pp));
+}
#endif
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index 336e52ec652c..5cc50d47ce3f 100644
--- a/arch/powerpc/mm/pgtable-radix.c
+++ b/arch/powerpc/mm/pgtable-radix.c
@@ -162,6 +162,14 @@ void radix__mark_rodata_ro(void)
radix__change_memory_range(start, end, _PAGE_WRITE);
}
+
+void radix__mark_initmem_nx(void)
+{
+ unsigned long start = (unsigned long)__init_begin;
+ unsigned long end = (unsigned long)__init_end;
+
+ radix__change_memory_range(start, end, _PAGE_EXEC);
+}
#endif /* CONFIG_STRICT_KERNEL_RWX */
static inline void __meminit print_mapping(unsigned long start,
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 5c0b795d656c..0736e94c7615 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -505,4 +505,12 @@ void mark_rodata_ro(void)
else
hash__mark_rodata_ro();
}
+
+void mark_initmem_nx(void)
+{
+ if (radix_enabled())
+ radix__mark_initmem_nx();
+ else
+ hash__mark_initmem_nx();
+}
#endif
