[PATCH 5.15 677/917] powerpc/book3e: Fix set_memory_x() and set_memory_nx()

Greg Kroah-Hartman
2021-11-15T23:59:41Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

[ Upstream commit b6cb20fdc2735f8b2e082937066c33fe376c2ee2 ]

set_memory_x() calls pte_mkexec() which sets _PAGE_EXEC.
set_memory_nx() calls pte_exprotec() which clears _PAGE_EXEC.

Book3e has 2 bits, UX and SX, which defines the exec rights
resp. for user (PR=1) and for kernel (PR=0).

_PAGE_EXEC is defined as UX only.

An executable kernel page is set with either _PAGE_KERNEL_RWX
or _PAGE_KERNEL_ROX, which both have SX set and UX cleared.

So set_memory_nx() call for an executable kernel page does
nothing because UX is already cleared.

And set_memory_x() on a non-executable kernel page makes it
executable for the user and keeps it non-executable for kernel.

Also, pte_exec() always returns 'false' on kernel pages, because
it checks _PAGE_EXEC which doesn't include SX, so for instance
the W+X check doesn't work.

To fix this:
- change tlb_low_64e.S to use _PAGE_BAP_UX instead of _PAGE_USER
- sets both UX and SX in _PAGE_EXEC so that pte_exec() returns
true whenever one of the two bits is set and pte_exprotect()
clears both bits.
- Define a book3e specific version of pte_mkexec() which sets
either SX or UX based on UR.

Fixes: 1f9ad21c3b38 ("powerpc/mm: Implement set_memory() routines")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c41100f9c144dc5b62e5a751b810190c6b5d42fd.1635226743.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/include/asm/nohash/32/pgtable.h | 2 ++
arch/powerpc/include/asm/nohash/64/pgtable.h | 5 -----
arch/powerpc/include/asm/nohash/pte-book3e.h | 18 ++++++++++++++----
arch/powerpc/mm/nohash/tlb_low_64e.S | 8 ++++----
4 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index ac0a5ff48c3ad..d6ba821a56ced 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -193,10 +193,12 @@ static inline pte_t pte_wrprotect(pte_t pte)
}
#endif

+#ifndef pte_mkexec
static inline pte_t pte_mkexec(pte_t pte)
{
return __pte(pte_val(pte) | _PAGE_EXEC);
}
+#endif

#define pmd_none(pmd) (!pmd_val(pmd))
#define pmd_bad(pmd) (pmd_val(pmd) & _PMD_BAD)
diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
index d081704b13fb9..9d2905a474103 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
@@ -118,11 +118,6 @@ static inline pte_t pte_wrprotect(pte_t pte)
return __pte(pte_val(pte) & ~_PAGE_RW);
}

-static inline pte_t pte_mkexec(pte_t pte)
-{
- return __pte(pte_val(pte) | _PAGE_EXEC);
-}
-
#define PMD_BAD_BITS (PTE_TABLE_SIZE-1)
#define PUD_BAD_BITS (PMD_TABLE_SIZE-1)

diff --git a/arch/powerpc/include/asm/nohash/pte-book3e.h b/arch/powerpc/include/asm/nohash/pte-book3e.h
index 813918f407653..f798640422c2d 100644
--- a/arch/powerpc/include/asm/nohash/pte-book3e.h
+++ b/arch/powerpc/include/asm/nohash/pte-book3e.h
@@ -48,7 +48,7 @@
#define _PAGE_WRITETHRU 0x800000 /* W: cache write-through */

/* "Higher level" linux bit combinations */
-#define _PAGE_EXEC _PAGE_BAP_UX /* .. and was cache cleaned */
+#define _PAGE_EXEC (_PAGE_BAP_SX | _PAGE_BAP_UX) /* .. and was cache cleaned */
#define _PAGE_RW (_PAGE_BAP_SW | _PAGE_BAP_UW) /* User write permission */
#define _PAGE_KERNEL_RW (_PAGE_BAP_SW | _PAGE_BAP_SR | _PAGE_DIRTY)
#define _PAGE_KERNEL_RO (_PAGE_BAP_SR)
@@ -93,11 +93,11 @@
/* Permission masks used to generate the __P and __S table */
#define PAGE_NONE __pgprot(_PAGE_BASE)
#define PAGE_SHARED __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW)
-#define PAGE_SHARED_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW | _PAGE_EXEC)
+#define PAGE_SHARED_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW | _PAGE_BAP_UX)
#define PAGE_COPY __pgprot(_PAGE_BASE | _PAGE_USER)
-#define PAGE_COPY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
+#define PAGE_COPY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_BAP_UX)
#define PAGE_READONLY __pgprot(_PAGE_BASE | _PAGE_USER)
-#define PAGE_READONLY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
+#define PAGE_READONLY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_BAP_UX)

#ifndef __ASSEMBLY__
static inline pte_t pte_mkprivileged(pte_t pte)
@@ -113,6 +113,16 @@ static inline pte_t pte_mkuser(pte_t pte)
}

#define pte_mkuser pte_mkuser
+
+static inline pte_t pte_mkexec(pte_t pte)
+{
+ if (pte_val(pte) & _PAGE_BAP_UR)
+ return __pte((pte_val(pte) & ~_PAGE_BAP_SX) | _PAGE_BAP_UX);
+ else
+ return __pte((pte_val(pte) & ~_PAGE_BAP_UX) | _PAGE_BAP_SX);
+}
+#define pte_mkexec pte_mkexec
+
#endif /* __ASSEMBLY__ */

#endif /* __KERNEL__ */
diff --git a/arch/powerpc/mm/nohash/tlb_low_64e.S b/arch/powerpc/mm/nohash/tlb_low_64e.S
index bf24451f3e71f..9235e720e3572 100644
--- a/arch/powerpc/mm/nohash/tlb_low_64e.S
+++ b/arch/powerpc/mm/nohash/tlb_low_64e.S
@@ -222,7 +222,7 @@ tlb_miss_kernel_bolted:

tlb_miss_fault_bolted:
/* We need to check if it was an instruction miss */
- andi. r10,r11,_PAGE_EXEC|_PAGE_BAP_SX
+ andi. r10,r11,_PAGE_BAP_UX|_PAGE_BAP_SX
bne itlb_miss_fault_bolted
dtlb_miss_fault_bolted:
tlb_epilog_bolted
@@ -239,7 +239,7 @@ itlb_miss_fault_bolted:
srdi r15,r16,60 /* get region */
bne- itlb_miss_fault_bolted

- li r11,_PAGE_PRESENT|_PAGE_EXEC /* Base perm */
+ li r11,_PAGE_PRESENT|_PAGE_BAP_UX /* Base perm */

/* We do the user/kernel test for the PID here along with the RW test
*/
@@ -614,7 +614,7 @@ itlb_miss_fault_e6500:

/* We do the user/kernel test for the PID here along with the RW test
*/
- li r11,_PAGE_PRESENT|_PAGE_EXEC /* Base perm */
+ li r11,_PAGE_PRESENT|_PAGE_BAP_UX /* Base perm */
oris r11,r11,_PAGE_ACCESSED@h

cmpldi cr0,r15,0 /* Check for user region */
@@ -734,7 +734,7 @@ normal_tlb_miss_done:

normal_tlb_miss_access_fault:
/* We need to check if it was an instruction miss */
- andi. r10,r11,_PAGE_EXEC
+ andi. r10,r11,_PAGE_BAP_UX
bne 1f
ld r14,EX_TLB_DEAR(r12)
ld r15,EX_TLB_ESR(r12)
--
2.33.0