[PATCH 5.16 098/121] arm64: Ensure execute-only permissions are not allowed without EPAN

Greg Kroah-Hartman
2022-03-14T12:33:36Z

From: Catalin Marinas <catalin.marinas@arm.com>

commit 6e2edd6371a497a6350bb735534c9bda2a31f43d upstream.

Commit 18107f8a2df6 ("arm64: Support execute-only permissions with
Enhanced PAN") re-introduced execute-only permissions when EPAN is
available. When EPAN is not available, arch_filter_pgprot() is supposed
to change a PAGE_EXECONLY permission into PAGE_READONLY_EXEC. However,
if BTI or MTE are present, such check does not detect the execute-only
pgprot in the presence of PTE_GP (BTI) or MT_NORMAL_TAGGED (MTE),
allowing the user to request PROT_EXEC with PROT_BTI or PROT_MTE.

Remove the arch_filter_pgprot() function, change the default VM_EXEC
permissions to PAGE_READONLY_EXEC and update the protection_map[] array
at core_initcall() if EPAN is detected.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: 18107f8a2df6 ("arm64: Support execute-only permissions with Enhanced PAN")
Cc: <stable@vger.kernel.org> # 5.13.x
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm64/Kconfig | 3 ---
arch/arm64/include/asm/pgtable-prot.h | 4 ++--
arch/arm64/include/asm/pgtable.h | 11 -----------
arch/arm64/mm/mmap.c | 17 +++++++++++++++++
4 files changed, 19 insertions(+), 16 deletions(-)

--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1264,9 +1264,6 @@ config HW_PERF_EVENTS
def_bool y
depends on ARM_PMU

-config ARCH_HAS_FILTER_PGPROT
- def_bool y
-
# Supported by clang >= 7.0
config CC_HAVE_SHADOW_CALL_STACK
def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -92,7 +92,7 @@ extern bool arm64_use_ng_mappings;
#define __P001 PAGE_READONLY
#define __P010 PAGE_READONLY
#define __P011 PAGE_READONLY
-#define __P100 PAGE_EXECONLY
+#define __P100 PAGE_READONLY_EXEC /* PAGE_EXECONLY if Enhanced PAN */
#define __P101 PAGE_READONLY_EXEC
#define __P110 PAGE_READONLY_EXEC
#define __P111 PAGE_READONLY_EXEC
@@ -101,7 +101,7 @@ extern bool arm64_use_ng_mappings;
#define __S001 PAGE_READONLY
#define __S010 PAGE_SHARED
#define __S011 PAGE_SHARED
-#define __S100 PAGE_EXECONLY
+#define __S100 PAGE_READONLY_EXEC /* PAGE_EXECONLY if Enhanced PAN */
#define __S101 PAGE_READONLY_EXEC
#define __S110 PAGE_SHARED_EXEC
#define __S111 PAGE_SHARED_EXEC
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1017,17 +1017,6 @@ static inline bool arch_wants_old_prefau
}
#define arch_wants_old_prefaulted_pte arch_wants_old_prefaulted_pte

-static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
-{
- if (cpus_have_const_cap(ARM64_HAS_EPAN))
- return prot;
-
- if (pgprot_val(prot) != pgprot_val(PAGE_EXECONLY))
- return prot;
-
- return PAGE_READONLY_EXEC;
-}
-
static inline bool pud_sect_supported(void)
{
return PAGE_SIZE == SZ_4K;
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -7,8 +7,10 @@

#include <linux/io.h>
#include <linux/memblock.h>
+#include <linux/mm.h>
#include <linux/types.h>

+#include <asm/cpufeature.h>
#include <asm/page.h>

/*
@@ -38,3 +40,18 @@ int valid_mmap_phys_addr_range(unsigned
{
return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
}
+
+static int __init adjust_protection_map(void)
+{
+ /*
+ * With Enhanced PAN we can honour the execute-only permissions as
+ * there is no PAN override with such mappings.
+ */
+ if (cpus_have_const_cap(ARM64_HAS_EPAN)) {
+ protection_map[VM_EXEC] = PAGE_EXECONLY;
+ protection_map[VM_EXEC | VM_SHARED] = PAGE_EXECONLY;
+ }
+
+ return 0;
+}
+arch_initcall(adjust_protection_map);