* [PATCH v5 1/8] powerpc/mm: Implement set_memory() routines
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 6:35 ` [PATCH v5 2/8] powerpc/kprobes: Mark newly allocated probes as RO Russell Currey
` (6 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, Russell Currey, npiggin, joel,
dja
From: Christophe Leroy <christophe.leroy@c-s.fr>
The set_memory_{ro/rw/nx/x}() functions are required for STRICT_MODULE_RWX,
and are generally useful primitives to have. This implementation is
designed to be completely generic across powerpc's many MMUs.
It's possible that this could be optimised to be faster for specific
MMUs, but the focus is on having a generic and safe implementation for
now.
This implementation does not handle cases where the caller is attempting
to change the mapping of the page it is executing from, or if another
CPU is concurrently using the page being altered. These cases likely
shouldn't happen, but a more complex implementation with MMU-specific code
could safely handle them, so that is left as a TODO for now.
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/set_memory.h | 32 ++++++++++++
arch/powerpc/mm/Makefile | 2 +-
arch/powerpc/mm/pageattr.c | 74 +++++++++++++++++++++++++++
4 files changed, 108 insertions(+), 1 deletion(-)
create mode 100644 arch/powerpc/include/asm/set_memory.h
create mode 100644 arch/powerpc/mm/pageattr.c
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 497b7d0b2d7e..bd074246e34e 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -129,6 +129,7 @@ config PPC
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_MEMBARRIER_CALLBACKS
select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
+ select ARCH_HAS_SET_MEMORY
select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UACCESS_FLUSHCACHE
diff --git a/arch/powerpc/include/asm/set_memory.h b/arch/powerpc/include/asm/set_memory.h
new file mode 100644
index 000000000000..64011ea444b4
--- /dev/null
+++ b/arch/powerpc/include/asm/set_memory.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_POWERPC_SET_MEMORY_H
+#define _ASM_POWERPC_SET_MEMORY_H
+
+#define SET_MEMORY_RO 0
+#define SET_MEMORY_RW 1
+#define SET_MEMORY_NX 2
+#define SET_MEMORY_X 3
+
+int change_memory_attr(unsigned long addr, int numpages, long action);
+
+static inline int set_memory_ro(unsigned long addr, int numpages)
+{
+ return change_memory_attr(addr, numpages, SET_MEMORY_RO);
+}
+
+static inline int set_memory_rw(unsigned long addr, int numpages)
+{
+ return change_memory_attr(addr, numpages, SET_MEMORY_RW);
+}
+
+static inline int set_memory_nx(unsigned long addr, int numpages)
+{
+ return change_memory_attr(addr, numpages, SET_MEMORY_NX);
+}
+
+static inline int set_memory_x(unsigned long addr, int numpages)
+{
+ return change_memory_attr(addr, numpages, SET_MEMORY_X);
+}
+
+#endif
diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
index 5e147986400d..a998fdac52f9 100644
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile
@@ -5,7 +5,7 @@
ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)
-obj-y := fault.o mem.o pgtable.o mmap.o \
+obj-y := fault.o mem.o pgtable.o mmap.o pageattr.o \
init_$(BITS).o pgtable_$(BITS).o \
pgtable-frag.o ioremap.o ioremap_$(BITS).o \
init-common.o mmu_context.o drmem.o
diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
new file mode 100644
index 000000000000..2b573768a7f7
--- /dev/null
+++ b/arch/powerpc/mm/pageattr.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * MMU-generic set_memory implementation for powerpc
+ *
+ * Copyright 2019, IBM Corporation.
+ */
+
+#include <linux/mm.h>
+#include <linux/set_memory.h>
+
+#include <asm/mmu.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+
+
+/*
+ * Updates the attributes of a page in three steps:
+ *
+ * 1. invalidate the page table entry
+ * 2. flush the TLB
+ * 3. install the new entry with the updated attributes
+ *
+ * This is unsafe if the caller is attempting to change the mapping of the
+ * page it is executing from, or if another CPU is concurrently using the
+ * page being altered.
+ *
+ * TODO make the implementation resistant to this.
+ */
+static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
+{
+ long action = (long)data;
+ pte_t pte;
+
+ spin_lock(&init_mm.page_table_lock);
+
+ /* invalidate the PTE so it's safe to modify */
+ pte = ptep_get_and_clear(&init_mm, addr, ptep);
+ flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+
+ /* modify the PTE bits as desired, then apply */
+ switch (action) {
+ case SET_MEMORY_RO:
+ pte = pte_wrprotect(pte);
+ break;
+ case SET_MEMORY_RW:
+ pte = pte_mkwrite(pte);
+ break;
+ case SET_MEMORY_NX:
+ pte = pte_exprotect(pte);
+ break;
+ case SET_MEMORY_X:
+ pte = pte_mkexec(pte);
+ break;
+ default:
+ break;
+ }
+
+ set_pte_at(&init_mm, addr, ptep, pte);
+ spin_unlock(&init_mm.page_table_lock);
+
+ return 0;
+}
+
+int change_memory_attr(unsigned long addr, int numpages, long action)
+{
+ unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
+ unsigned long sz = numpages * PAGE_SIZE;
+
+ if (!numpages)
+ return 0;
+
+ return apply_to_page_range(&init_mm, start, sz, change_page_attr, (void *)action);
+}
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 2/8] powerpc/kprobes: Mark newly allocated probes as RO
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
2020-02-26 6:35 ` [PATCH v5 1/8] powerpc/mm: Implement set_memory() routines Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 6:35 ` [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Russell Currey
` (5 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, Russell Currey, npiggin, joel,
dja
From: Christophe Leroy <christophe.leroy@c-s.fr>
With CONFIG_STRICT_KERNEL_RWX=y and CONFIG_KPROBES=y, there will be one
W+X page at boot by default. This can be tested with
CONFIG_PPC_PTDUMP=y and CONFIG_PPC_DEBUG_WX=y set, and checking the
kernel log during boot.
powerpc doesn't implement its own alloc() for kprobes like other
architectures do, but we couldn't immediately mark RO anyway since we do
a memcpy to the page we allocate later. After that, nothing should be
allowed to modify the page, and write permissions are removed well
before the kprobe is armed.
The memcpy() would fail if >1 probes were allocated, so use
patch_instruction() instead which is safe for RO.
Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/kernel/kprobes.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 2d27ec4feee4..bfab91ded234 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -24,6 +24,8 @@
#include <asm/sstep.h>
#include <asm/sections.h>
#include <linux/uaccess.h>
+#include <linux/set_memory.h>
+#include <linux/vmalloc.h>
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -102,6 +104,16 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
return addr;
}
+void *alloc_insn_page(void)
+{
+ void *page = vmalloc_exec(PAGE_SIZE);
+
+ if (page)
+ set_memory_ro((unsigned long)page, 1);
+
+ return page;
+}
+
int arch_prepare_kprobe(struct kprobe *p)
{
int ret = 0;
@@ -124,11 +136,8 @@ int arch_prepare_kprobe(struct kprobe *p)
}
if (!ret) {
- memcpy(p->ainsn.insn, p->addr,
- MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+ patch_instruction(p->ainsn.insn, *p->addr);
p->opcode = *p->addr;
- flush_icache_range((unsigned long)p->ainsn.insn,
- (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
}
p->ainsn.boostable = 0;
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
2020-02-26 6:35 ` [PATCH v5 1/8] powerpc/mm: Implement set_memory() routines Russell Currey
2020-02-26 6:35 ` [PATCH v5 2/8] powerpc/kprobes: Mark newly allocated probes as RO Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 21:52 ` Kees Cook
2022-04-06 18:55 ` Kees Cook
2020-02-26 6:35 ` [PATCH v5 4/8] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX Russell Currey
` (4 subsequent siblings)
7 siblings, 2 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, Russell Currey, npiggin, joel,
dja
Very rudimentary, just
echo 1 > [debugfs]/check_wx_pages
and check the kernel log. Useful for testing strict module RWX.
Updated the Kconfig entry to reflect this.
Also fixed a typo.
Signed-off-by: Russell Currey <ruscur@russell.cc>
---
arch/powerpc/Kconfig.debug | 6 ++++--
arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
2 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 0b063830eea8..e37960ef68c6 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -370,7 +370,7 @@ config PPC_PTDUMP
If you are unsure, say N.
config PPC_DEBUG_WX
- bool "Warn on W+X mappings at boot"
+ bool "Warn on W+X mappings at boot & enable manual checks at runtime"
depends on PPC_PTDUMP && STRICT_KERNEL_RWX
help
Generate a warning if any W+X mappings are found at boot.
@@ -384,7 +384,9 @@ config PPC_DEBUG_WX
of other unfixed kernel bugs easier.
There is no runtime or memory usage effect of this option
- once the kernel has booted up - it's a one time check.
+ once the kernel has booted up, it only automatically checks once.
+
+ Enables the "check_wx_pages" debugfs entry for checking at runtime.
If in doubt, say "Y".
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 206156255247..a15e19a3b14e 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -4,7 +4,7 @@
*
* This traverses the kernel pagetables and dumps the
* information about the used sections of memory to
- * /sys/kernel/debug/kernel_pagetables.
+ * /sys/kernel/debug/kernel_page_tables.
*
* Derived from the arm64 implementation:
* Copyright (c) 2014, The Linux Foundation, Laura Abbott.
@@ -413,6 +413,25 @@ void ptdump_check_wx(void)
else
pr_info("Checked W+X mappings: passed, no W+X pages found\n");
}
+
+static int check_wx_debugfs_set(void *data, u64 val)
+{
+ if (val != 1ULL)
+ return -EINVAL;
+
+ ptdump_check_wx();
+
+ return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
+
+static int ptdump_check_wx_init(void)
+{
+ return debugfs_create_file("check_wx_pages", 0200, NULL,
+ NULL, &check_wx_fops) ? 0 : -ENOMEM;
+}
+device_initcall(ptdump_check_wx_init);
#endif
static int ptdump_init(void)
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
2020-02-26 6:35 ` [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Russell Currey
@ 2020-02-26 21:52 ` Kees Cook
2022-04-06 18:55 ` Kees Cook
1 sibling, 0 replies; 14+ messages in thread
From: Kees Cook @ 2020-02-26 21:52 UTC (permalink / raw)
To: Russell Currey
Cc: ajd, kernel-hardening, jniethe5, npiggin, joel, linuxppc-dev, dja
On Wed, Feb 26, 2020 at 05:35:46PM +1100, Russell Currey wrote:
> Very rudimentary, just
>
> echo 1 > [debugfs]/check_wx_pages
>
> and check the kernel log. Useful for testing strict module RWX.
>
> Updated the Kconfig entry to reflect this.
Oh, I like this! This would be handy to have on all architectures.
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
>
> Also fixed a typo.
>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> ---
> arch/powerpc/Kconfig.debug | 6 ++++--
> arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
> 2 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> index 0b063830eea8..e37960ef68c6 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -370,7 +370,7 @@ config PPC_PTDUMP
> If you are unsure, say N.
>
> config PPC_DEBUG_WX
> - bool "Warn on W+X mappings at boot"
> + bool "Warn on W+X mappings at boot & enable manual checks at runtime"
> depends on PPC_PTDUMP && STRICT_KERNEL_RWX
> help
> Generate a warning if any W+X mappings are found at boot.
> @@ -384,7 +384,9 @@ config PPC_DEBUG_WX
> of other unfixed kernel bugs easier.
>
> There is no runtime or memory usage effect of this option
> - once the kernel has booted up - it's a one time check.
> + once the kernel has booted up, it only automatically checks once.
> +
> + Enables the "check_wx_pages" debugfs entry for checking at runtime.
>
> If in doubt, say "Y".
>
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> index 206156255247..a15e19a3b14e 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -4,7 +4,7 @@
> *
> * This traverses the kernel pagetables and dumps the
> * information about the used sections of memory to
> - * /sys/kernel/debug/kernel_pagetables.
> + * /sys/kernel/debug/kernel_page_tables.
> *
> * Derived from the arm64 implementation:
> * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
> @@ -413,6 +413,25 @@ void ptdump_check_wx(void)
> else
> pr_info("Checked W+X mappings: passed, no W+X pages found\n");
> }
> +
> +static int check_wx_debugfs_set(void *data, u64 val)
> +{
> + if (val != 1ULL)
> + return -EINVAL;
> +
> + ptdump_check_wx();
> +
> + return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> +
> +static int ptdump_check_wx_init(void)
> +{
> + return debugfs_create_file("check_wx_pages", 0200, NULL,
> + NULL, &check_wx_fops) ? 0 : -ENOMEM;
> +}
> +device_initcall(ptdump_check_wx_init);
> #endif
>
> static int ptdump_init(void)
> --
> 2.25.1
>
--
Kees Cook
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
2020-02-26 6:35 ` [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Russell Currey
2020-02-26 21:52 ` Kees Cook
@ 2022-04-06 18:55 ` Kees Cook
2022-04-07 7:39 ` Christophe Leroy
1 sibling, 1 reply; 14+ messages in thread
From: Kees Cook @ 2022-04-06 18:55 UTC (permalink / raw)
To: Russell Currey
Cc: ajd, jniethe5, npiggin, joel, dja, linuxppc-dev, linux-hardening
*thread necromancy*
Is this patch still something folks are working on? It'd be nice to be
able to trigger this check at runtime.
-Kees
On Wed, Feb 26, 2020 at 05:35:46PM +1100, Russell Currey wrote:
> Very rudimentary, just
>
> echo 1 > [debugfs]/check_wx_pages
>
> and check the kernel log. Useful for testing strict module RWX.
>
> Updated the Kconfig entry to reflect this.
>
> Also fixed a typo.
>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> ---
> arch/powerpc/Kconfig.debug | 6 ++++--
> arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
> 2 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> index 0b063830eea8..e37960ef68c6 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -370,7 +370,7 @@ config PPC_PTDUMP
> If you are unsure, say N.
>
> config PPC_DEBUG_WX
> - bool "Warn on W+X mappings at boot"
> + bool "Warn on W+X mappings at boot & enable manual checks at runtime"
> depends on PPC_PTDUMP && STRICT_KERNEL_RWX
> help
> Generate a warning if any W+X mappings are found at boot.
> @@ -384,7 +384,9 @@ config PPC_DEBUG_WX
> of other unfixed kernel bugs easier.
>
> There is no runtime or memory usage effect of this option
> - once the kernel has booted up - it's a one time check.
> + once the kernel has booted up, it only automatically checks once.
> +
> + Enables the "check_wx_pages" debugfs entry for checking at runtime.
>
> If in doubt, say "Y".
>
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> index 206156255247..a15e19a3b14e 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -4,7 +4,7 @@
> *
> * This traverses the kernel pagetables and dumps the
> * information about the used sections of memory to
> - * /sys/kernel/debug/kernel_pagetables.
> + * /sys/kernel/debug/kernel_page_tables.
> *
> * Derived from the arm64 implementation:
> * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
> @@ -413,6 +413,25 @@ void ptdump_check_wx(void)
> else
> pr_info("Checked W+X mappings: passed, no W+X pages found\n");
> }
> +
> +static int check_wx_debugfs_set(void *data, u64 val)
> +{
> + if (val != 1ULL)
> + return -EINVAL;
> +
> + ptdump_check_wx();
> +
> + return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> +
> +static int ptdump_check_wx_init(void)
> +{
> + return debugfs_create_file("check_wx_pages", 0200, NULL,
> + NULL, &check_wx_fops) ? 0 : -ENOMEM;
> +}
> +device_initcall(ptdump_check_wx_init);
> #endif
>
> static int ptdump_init(void)
> --
> 2.25.1
>
--
Kees Cook
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
2022-04-06 18:55 ` Kees Cook
@ 2022-04-07 7:39 ` Christophe Leroy
0 siblings, 0 replies; 14+ messages in thread
From: Christophe Leroy @ 2022-04-07 7:39 UTC (permalink / raw)
To: Kees Cook, Russell Currey, jniethe5@gmail.com
Cc: ajd@linux.ibm.com, joel@jms.id.au, npiggin@gmail.com,
linux-hardening@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
dja@axtens.net
Le 06/04/2022 à 20:55, Kees Cook a écrit :
> *thread necromancy*
>
> Is this patch still something folks are working on? It'd be nice to be
> able to trigger this check at runtime.
The series was taken over by Jordan.
v15 of the series was accepted, but that particular patch was dropped in
v11 (see
https://patchwork.ozlabs.org/project/linuxppc-dev/cover/20210429031602.2606654-1-jniethe5@gmail.com/)
The comment was:
Some patches were dropped from this revision:
powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
- Will use Christophe's generic ptdump series
Not sure what happened after that.
Christophe
>
> -Kees
>
> On Wed, Feb 26, 2020 at 05:35:46PM +1100, Russell Currey wrote:
>> Very rudimentary, just
>>
>> echo 1 > [debugfs]/check_wx_pages
>>
>> and check the kernel log. Useful for testing strict module RWX.
>>
>> Updated the Kconfig entry to reflect this.
>>
>> Also fixed a typo.
>>
>> Signed-off-by: Russell Currey <ruscur@russell.cc>
>> ---
>> arch/powerpc/Kconfig.debug | 6 ++++--
>> arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
>> 2 files changed, 24 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
>> index 0b063830eea8..e37960ef68c6 100644
>> --- a/arch/powerpc/Kconfig.debug
>> +++ b/arch/powerpc/Kconfig.debug
>> @@ -370,7 +370,7 @@ config PPC_PTDUMP
>> If you are unsure, say N.
>>
>> config PPC_DEBUG_WX
>> - bool "Warn on W+X mappings at boot"
>> + bool "Warn on W+X mappings at boot & enable manual checks at runtime"
>> depends on PPC_PTDUMP && STRICT_KERNEL_RWX
>> help
>> Generate a warning if any W+X mappings are found at boot.
>> @@ -384,7 +384,9 @@ config PPC_DEBUG_WX
>> of other unfixed kernel bugs easier.
>>
>> There is no runtime or memory usage effect of this option
>> - once the kernel has booted up - it's a one time check.
>> + once the kernel has booted up, it only automatically checks once.
>> +
>> + Enables the "check_wx_pages" debugfs entry for checking at runtime.
>>
>> If in doubt, say "Y".
>>
>> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
>> index 206156255247..a15e19a3b14e 100644
>> --- a/arch/powerpc/mm/ptdump/ptdump.c
>> +++ b/arch/powerpc/mm/ptdump/ptdump.c
>> @@ -4,7 +4,7 @@
>> *
>> * This traverses the kernel pagetables and dumps the
>> * information about the used sections of memory to
>> - * /sys/kernel/debug/kernel_pagetables.
>> + * /sys/kernel/debug/kernel_page_tables.
>> *
>> * Derived from the arm64 implementation:
>> * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
>> @@ -413,6 +413,25 @@ void ptdump_check_wx(void)
>> else
>> pr_info("Checked W+X mappings: passed, no W+X pages found\n");
>> }
>> +
>> +static int check_wx_debugfs_set(void *data, u64 val)
>> +{
>> + if (val != 1ULL)
>> + return -EINVAL;
>> +
>> + ptdump_check_wx();
>> +
>> + return 0;
>> +}
>> +
>> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
>> +
>> +static int ptdump_check_wx_init(void)
>> +{
>> + return debugfs_create_file("check_wx_pages", 0200, NULL,
>> + NULL, &check_wx_fops) ? 0 : -ENOMEM;
>> +}
>> +device_initcall(ptdump_check_wx_init);
>> #endif
>>
>> static int ptdump_init(void)
>> --
>> 2.25.1
>>
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v5 4/8] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
` (2 preceding siblings ...)
2020-02-26 6:35 ` [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 6:35 ` [PATCH v5 5/8] powerpc/configs: Enable STRICT_MODULE_RWX in skiroot_defconfig Russell Currey
` (3 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, Russell Currey, npiggin, joel,
dja
To enable strict module RWX on powerpc, set:
CONFIG_STRICT_MODULE_RWX=y
You should also have CONFIG_STRICT_KERNEL_RWX=y set to have any real
security benefit.
ARCH_HAS_STRICT_MODULE_RWX is set to require ARCH_HAS_STRICT_KERNEL_RWX.
This is due to a quirk in arch/Kconfig and arch/powerpc/Kconfig that
makes STRICT_MODULE_RWX *on by default* in configurations where
STRICT_KERNEL_RWX is *unavailable*.
Since this doesn't make much sense, and module RWX without kernel RWX
doesn't make much sense, having the same dependencies as kernel RWX
works around this problem.
Signed-off-by: Russell Currey <ruscur@russell.cc>
---
arch/powerpc/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index bd074246e34e..e1fc7fba10bf 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -131,6 +131,7 @@ config PPC
select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
select ARCH_HAS_SET_MEMORY
select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
+ select ARCH_HAS_STRICT_MODULE_RWX if ARCH_HAS_STRICT_KERNEL_RWX
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UACCESS_FLUSHCACHE
select ARCH_HAS_UACCESS_MCSAFE if PPC64
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 5/8] powerpc/configs: Enable STRICT_MODULE_RWX in skiroot_defconfig
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
` (3 preceding siblings ...)
2020-02-26 6:35 ` [PATCH v5 4/8] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 6:35 ` [PATCH v5 6/8] powerpc/mm: implement set_memory_attr() Russell Currey
` (2 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, Russell Currey, Joel Stanley,
npiggin, joel, dja
skiroot_defconfig is the only powerpc defconfig with STRICT_KERNEL_RWX
enabled, and if you want memory protection for kernel text you'd want it
for modules too, so enable STRICT_MODULE_RWX there.
Acked-by: Joel Stanley <joel@joel.id.au>
Signed-off-by: Russell Currey <ruscur@russell.cc>
---
arch/powerpc/configs/skiroot_defconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/configs/skiroot_defconfig b/arch/powerpc/configs/skiroot_defconfig
index 1b6bdad36b13..66d20dbe67b7 100644
--- a/arch/powerpc/configs/skiroot_defconfig
+++ b/arch/powerpc/configs/skiroot_defconfig
@@ -51,6 +51,7 @@ CONFIG_CMDLINE="console=tty0 console=hvc0 ipr.fast_reboot=1 quiet"
# CONFIG_PPC_MEM_KEYS is not set
CONFIG_JUMP_LABEL=y
CONFIG_STRICT_KERNEL_RWX=y
+CONFIG_STRICT_MODULE_RWX=y
CONFIG_MODULES=y
CONFIG_MODULE_UNLOAD=y
CONFIG_MODULE_SIG_FORCE=y
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 6/8] powerpc/mm: implement set_memory_attr()
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
` (4 preceding siblings ...)
2020-02-26 6:35 ` [PATCH v5 5/8] powerpc/configs: Enable STRICT_MODULE_RWX in skiroot_defconfig Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 6:35 ` [PATCH v5 7/8] powerpc/32: use set_memory_attr() Russell Currey
2020-02-26 6:35 ` [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled Russell Currey
7 siblings, 0 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, Russell Currey, npiggin,
kbuild test robot, joel, dja
From: Christophe Leroy <christophe.leroy@c-s.fr>
In addition to the set_memory_xx() functions which allows to change
the memory attributes of not (yet) used memory regions, implement a
set_memory_attr() function to:
- set the final memory protection after init on currently used
kernel regions.
- enable/disable kernel memory regions in the scope of DEBUG_PAGEALLOC.
Unlike the set_memory_xx() which can act in three step as the regions
are unused, this function must modify 'on the fly' as the kernel is
executing from them. At the moment only PPC32 will use it and changing
page attributes on the fly is not an issue.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reported-by: kbuild test robot <lkp@intel.com>
[ruscur: cast "data" to unsigned long instead of int]
Signed-off-by: Russell Currey <ruscur@russell.cc>
---
v4: cast "data" to unsigned long instead of int
arch/powerpc/include/asm/set_memory.h | 2 ++
arch/powerpc/mm/pageattr.c | 33 +++++++++++++++++++++++++++
2 files changed, 35 insertions(+)
diff --git a/arch/powerpc/include/asm/set_memory.h b/arch/powerpc/include/asm/set_memory.h
index 64011ea444b4..b040094f7920 100644
--- a/arch/powerpc/include/asm/set_memory.h
+++ b/arch/powerpc/include/asm/set_memory.h
@@ -29,4 +29,6 @@ static inline int set_memory_x(unsigned long addr, int numpages)
return change_memory_attr(addr, numpages, SET_MEMORY_X);
}
+int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot);
+
#endif
diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
index 2b573768a7f7..ee6b5e3b7604 100644
--- a/arch/powerpc/mm/pageattr.c
+++ b/arch/powerpc/mm/pageattr.c
@@ -72,3 +72,36 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
return apply_to_page_range(&init_mm, start, sz, change_page_attr, (void *)action);
}
+
+/*
+ * Set the attributes of a page:
+ *
+ * This function is used by PPC32 at the end of init to set final kernel memory
+ * protection. It includes changing the maping of the page it is executing from
+ * and data pages it is using.
+ */
+static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
+{
+ pgprot_t prot = __pgprot((unsigned long)data);
+
+ spin_lock(&init_mm.page_table_lock);
+
+ set_pte_at(&init_mm, addr, ptep, pte_modify(*ptep, prot));
+ flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+
+ spin_unlock(&init_mm.page_table_lock);
+
+ return 0;
+}
+
+int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
+{
+ unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
+ unsigned long sz = numpages * PAGE_SIZE;
+
+ if (!numpages)
+ return 0;
+
+ return apply_to_page_range(&init_mm, start, sz, set_page_attr,
+ (void *)pgprot_val(prot));
+}
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 7/8] powerpc/32: use set_memory_attr()
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
` (5 preceding siblings ...)
2020-02-26 6:35 ` [PATCH v5 6/8] powerpc/mm: implement set_memory_attr() Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 6:35 ` [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled Russell Currey
7 siblings, 0 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev; +Cc: ajd, kernel-hardening, jniethe5, npiggin, joel, dja
From: Christophe Leroy <christophe.leroy@c-s.fr>
Use set_memory_attr() instead of the PPC32 specific change_page_attr()
change_page_attr() was checking that the address was not mapped by
blocks and was handling highmem, but that's unneeded because the
affected pages can't be in highmem and block mapping verification
is already done by the callers.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/mm/pgtable_32.c | 95 ++++--------------------------------
1 file changed, 10 insertions(+), 85 deletions(-)
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 5fb90edd865e..3d92eaf3ee2f 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -23,6 +23,7 @@
#include <linux/highmem.h>
#include <linux/memblock.h>
#include <linux/slab.h>
+#include <linux/set_memory.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -121,99 +122,20 @@ void __init mapin_ram(void)
}
}
-/* Scan the real Linux page tables and return a PTE pointer for
- * a virtual address in a context.
- * Returns true (1) if PTE was found, zero otherwise. The pointer to
- * the PTE pointer is unmodified if PTE is not found.
- */
-static int
-get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
-{
- pgd_t *pgd;
- pud_t *pud;
- pmd_t *pmd;
- pte_t *pte;
- int retval = 0;
-
- pgd = pgd_offset(mm, addr & PAGE_MASK);
- if (pgd) {
- pud = pud_offset(pgd, addr & PAGE_MASK);
- if (pud && pud_present(*pud)) {
- pmd = pmd_offset(pud, addr & PAGE_MASK);
- if (pmd_present(*pmd)) {
- pte = pte_offset_map(pmd, addr & PAGE_MASK);
- if (pte) {
- retval = 1;
- *ptep = pte;
- if (pmdp)
- *pmdp = pmd;
- /* XXX caller needs to do pte_unmap, yuck */
- }
- }
- }
- }
- return(retval);
-}
-
-static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
-{
- pte_t *kpte;
- pmd_t *kpmd;
- unsigned long address;
-
- BUG_ON(PageHighMem(page));
- address = (unsigned long)page_address(page);
-
- if (v_block_mapped(address))
- return 0;
- if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
- return -EINVAL;
- __set_pte_at(&init_mm, address, kpte, mk_pte(page, prot), 0);
- pte_unmap(kpte);
-
- return 0;
-}
-
-/*
- * Change the page attributes of an page in the linear mapping.
- *
- * THIS DOES NOTHING WITH BAT MAPPINGS, DEBUG USE ONLY
- */
-static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
-{
- int i, err = 0;
- unsigned long flags;
- struct page *start = page;
-
- local_irq_save(flags);
- for (i = 0; i < numpages; i++, page++) {
- err = __change_page_attr_noflush(page, prot);
- if (err)
- break;
- }
- wmb();
- local_irq_restore(flags);
- flush_tlb_kernel_range((unsigned long)page_address(start),
- (unsigned long)page_address(page));
- return err;
-}
-
void mark_initmem_nx(void)
{
- struct page *page = virt_to_page(_sinittext);
unsigned long numpages = PFN_UP((unsigned long)_einittext) -
PFN_DOWN((unsigned long)_sinittext);
if (v_block_mapped((unsigned long)_stext + 1))
mmu_mark_initmem_nx();
else
- change_page_attr(page, numpages, PAGE_KERNEL);
+ set_memory_attr((unsigned long)_sinittext, numpages, PAGE_KERNEL);
}
#ifdef CONFIG_STRICT_KERNEL_RWX
void mark_rodata_ro(void)
{
- struct page *page;
unsigned long numpages;
if (v_block_mapped((unsigned long)_sinittext)) {
@@ -222,20 +144,18 @@ void mark_rodata_ro(void)
return;
}
- page = virt_to_page(_stext);
numpages = PFN_UP((unsigned long)_etext) -
PFN_DOWN((unsigned long)_stext);
- change_page_attr(page, numpages, PAGE_KERNEL_ROX);
+ set_memory_attr((unsigned long)_stext, numpages, PAGE_KERNEL_ROX);
/*
* mark .rodata as read only. Use __init_begin rather than __end_rodata
* to cover NOTES and EXCEPTION_TABLE.
*/
- page = virt_to_page(__start_rodata);
numpages = PFN_UP((unsigned long)__init_begin) -
PFN_DOWN((unsigned long)__start_rodata);
- change_page_attr(page, numpages, PAGE_KERNEL_RO);
+ set_memory_attr((unsigned long)__start_rodata, numpages, PAGE_KERNEL_RO);
// mark_initmem_nx() should have already run by now
ptdump_check_wx();
@@ -245,9 +165,14 @@ void mark_rodata_ro(void)
#ifdef CONFIG_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable)
{
+ unsigned long addr = (unsigned long)page_address(page);
+
if (PageHighMem(page))
return;
- change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
+ if (enable)
+ set_memory_attr(addr, numpages, PAGE_KERNEL);
+ else
+ set_memory_attr(addr, numpages, __pgprot(0));
}
#endif /* CONFIG_DEBUG_PAGEALLOC */
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled
2020-02-26 6:35 [PATCH v5 0/8] set_memory() routines and STRICT_MODULE_RWX Russell Currey
` (6 preceding siblings ...)
2020-02-26 6:35 ` [PATCH v5 7/8] powerpc/32: use set_memory_attr() Russell Currey
@ 2020-02-26 6:35 ` Russell Currey
2020-02-26 6:38 ` Andrew Donnellan
2020-02-26 7:29 ` Christophe Leroy
7 siblings, 2 replies; 14+ messages in thread
From: Russell Currey @ 2020-02-26 6:35 UTC (permalink / raw)
To: linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, Russell Currey, npiggin, joel,
dja
There are a couple of reasons that the set_memory() functions are
problematic when STRICT_KERNEL_RWX isn't enabled:
- The linear mapping is a different size and apply_to_page_range()
may modify a giant section, breaking everything
- patch_instruction() doesn't know to work around a page being marked
RO, and will subsequently crash
The latter can be replicated by building a kernel with the set_memory()
patches but with STRICT_KERNEL_RWX off and running ftracetest.
Reported-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>
---
v5: Apply to both set_memory_attr() and change_memory_attr()
v4: New
arch/powerpc/mm/pageattr.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
index ee6b5e3b7604..49b8e2e0581d 100644
--- a/arch/powerpc/mm/pageattr.c
+++ b/arch/powerpc/mm/pageattr.c
@@ -64,13 +64,18 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
int change_memory_attr(unsigned long addr, int numpages, long action)
{
- unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
- unsigned long sz = numpages * PAGE_SIZE;
+ unsigned long start, size;
+
+ if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
+ return 0;
if (!numpages)
return 0;
- return apply_to_page_range(&init_mm, start, sz, change_page_attr, (void *)action);
+ start = ALIGN_DOWN(addr, PAGE_SIZE);
+ size = numpages * PAGE_SIZE;
+
+ return apply_to_page_range(&init_mm, start, size, change_page_attr, (void *)action);
}
/*
@@ -96,12 +101,17 @@ static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
{
- unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
- unsigned long sz = numpages * PAGE_SIZE;
+ unsigned long start, size;
+
+ if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
+ return 0;
if (!numpages)
return 0;
- return apply_to_page_range(&init_mm, start, sz, set_page_attr,
+ start = ALIGN_DOWN(addr, PAGE_SIZE);
+ size = numpages * PAGE_SIZE;
+
+ return apply_to_page_range(&init_mm, start, size, set_page_attr,
(void *)pgprot_val(prot));
}
--
2.25.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled
2020-02-26 6:35 ` [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled Russell Currey
@ 2020-02-26 6:38 ` Andrew Donnellan
2020-02-26 7:29 ` Christophe Leroy
1 sibling, 0 replies; 14+ messages in thread
From: Andrew Donnellan @ 2020-02-26 6:38 UTC (permalink / raw)
To: Russell Currey, linuxppc-dev
Cc: kernel-hardening, jniethe5, npiggin, joel, dja
On 26/2/20 5:35 pm, Russell Currey wrote:
> There are a couple of reasons that the set_memory() functions are
> problematic when STRICT_KERNEL_RWX isn't enabled:
>
> - The linear mapping is a different size and apply_to_page_range()
> may modify a giant section, breaking everything
> - patch_instruction() doesn't know to work around a page being marked
> RO, and will subsequently crash
>
> The latter can be replicated by building a kernel with the set_memory()
> patches but with STRICT_KERNEL_RWX off and running ftracetest.
>
> Reported-by: Jordan Niethe <jniethe5@gmail.com>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
Can we squash this in earlier in the series for the sake of bisectability?
--
Andrew Donnellan OzLabs, ADL Canberra
ajd@linux.ibm.com IBM Australia Limited
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled
2020-02-26 6:35 ` [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled Russell Currey
2020-02-26 6:38 ` Andrew Donnellan
@ 2020-02-26 7:29 ` Christophe Leroy
1 sibling, 0 replies; 14+ messages in thread
From: Christophe Leroy @ 2020-02-26 7:29 UTC (permalink / raw)
To: Russell Currey, linuxppc-dev
Cc: ajd, kernel-hardening, jniethe5, npiggin, joel, dja
Le 26/02/2020 à 07:35, Russell Currey a écrit :
> There are a couple of reasons that the set_memory() functions are
> problematic when STRICT_KERNEL_RWX isn't enabled:
>
> - The linear mapping is a different size and apply_to_page_range()
> may modify a giant section, breaking everything
> - patch_instruction() doesn't know to work around a page being marked
> RO, and will subsequently crash
>
> The latter can be replicated by building a kernel with the set_memory()
> patches but with STRICT_KERNEL_RWX off and running ftracetest.
I agree with Andrew, those changes should go into patch 1.
>
> Reported-by: Jordan Niethe <jniethe5@gmail.com>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> ---
> v5: Apply to both set_memory_attr() and change_memory_attr()
See my comments of v4, additional comments below
> v4: New
>
> arch/powerpc/mm/pageattr.c | 22 ++++++++++++++++------
> 1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
> index ee6b5e3b7604..49b8e2e0581d 100644
> --- a/arch/powerpc/mm/pageattr.c
> +++ b/arch/powerpc/mm/pageattr.c
> @@ -64,13 +64,18 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
>
> int change_memory_attr(unsigned long addr, int numpages, long action)
> {
> - unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
> - unsigned long sz = numpages * PAGE_SIZE;
> + unsigned long start, size;
> +
> + if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
> + return 0;
>
> if (!numpages)
> return 0;
>
> - return apply_to_page_range(&init_mm, start, sz, change_page_attr, (void *)action);
> + start = ALIGN_DOWN(addr, PAGE_SIZE);
> + size = numpages * PAGE_SIZE;
> +
> + return apply_to_page_range(&init_mm, start, size, change_page_attr, (void *)action);
You don't need to move start and sz initialisation, neither you need to
change the name of sz to size.
If you want to rename sz to size, do it in the initial patch, but take
care of the length of the lines. IIRC I used a short name to have the
line fit on a single line with no more than 90 chars.
Christophe
> }
>
> /*
> @@ -96,12 +101,17 @@ static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
>
> int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
> {
> - unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
> - unsigned long sz = numpages * PAGE_SIZE;
> + unsigned long start, size;
> +
> + if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
> + return 0;
>
> if (!numpages)
> return 0;
>
> - return apply_to_page_range(&init_mm, start, sz, set_page_attr,
> + start = ALIGN_DOWN(addr, PAGE_SIZE);
> + size = numpages * PAGE_SIZE;
> +
> + return apply_to_page_range(&init_mm, start, size, set_page_attr,
> (void *)pgprot_val(prot));
> }
>
^ permalink raw reply [flat|nested] 14+ messages in thread