[PATCH] arm64: Fix text patching logic when using fixmap

[PATCH] arm64: Fix text patching logic when using fixmap

[Marc Zyngier]

Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
the way we patch the kernel text, using a fixmap when the kernel or
modules are flagged as read only.

Unfortunately, a flaw in the logic makes it fall over when patching
modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:

[...]
[   32.032636] Call trace:
[   32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
[   32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
[   32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
[   32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
[   32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
[   32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
[   32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
[   32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
[   32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
[...]

This is triggered by the use of virt_to_page() on a module address,
which ends to pointing to Nowhereland if you're lucky, or corrupt
your precious data if not.

This patch fixes the logic by mimicking what is done on arm:
- If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
  use vmalloc_to_page().
- If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
  use virt_to_page().
- Otherwise, use the provided address, as we can write to it directly.

Tested on 4.0-rc1 as a KVM guest.

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm64/kernel/insn.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 27d4864..c8eca88 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -87,8 +87,10 @@ static void __kprobes *patch_map(void *addr, int fixmap)
 
 	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
 		page = vmalloc_to_page(addr);
-	else
+	else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
 		page = virt_to_page(addr);
+	else
+		return addr;
 
 	BUG_ON(!page);
 	set_fixmap(fixmap, page_to_phys(page));
-- 
2.1.4

[PATCH] arm64: Fix text patching logic when using fixmap

[Kees Cook]

On Tue, Feb 24, 2015 at 8:30 AM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
> the way we patch the kernel text, using a fixmap when the kernel or
> modules are flagged as read only.
>
> Unfortunately, a flaw in the logic makes it fall over when patching
> modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:
>
> [...]
> [   32.032636] Call trace:
> [   32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
> [   32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
> [   32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
> [   32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
> [   32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
> [   32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
> [   32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
> [   32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
> [   32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
> [...]
>
> This is triggered by the use of virt_to_page() on a module address,
> which ends to pointing to Nowhereland if you're lucky, or corrupt
> your precious data if not.
>
> This patch fixes the logic by mimicking what is done on arm:
> - If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
>   use vmalloc_to_page().
> - If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
>   use virt_to_page().
> - Otherwise, use the provided address, as we can write to it directly.
>
> Tested on 4.0-rc1 as a KVM guest.
>
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Laura Abbott <lauraa@codeaurora.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Good catch! Looks fine to me.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  arch/arm64/kernel/insn.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 27d4864..c8eca88 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -87,8 +87,10 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>
>         if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
>                 page = vmalloc_to_page(addr);
> -       else
> +       else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
>                 page = virt_to_page(addr);
> +       else
> +               return addr;
>
>         BUG_ON(!page);
>         set_fixmap(fixmap, page_to_phys(page));
> --
> 2.1.4
>



-- 
Kees Cook
Chrome OS Security

[PATCH] arm64: Fix text patching logic when using fixmap

[Mark Rutland]

On Tue, Feb 24, 2015 at 04:30:21PM +0000, Marc Zyngier wrote:
> Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
> the way we patch the kernel text, using a fixmap when the kernel or
> modules are flagged as read only.
> 
> Unfortunately, a flaw in the logic makes it fall over when patching
> modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:
> 
> [...]
> [   32.032636] Call trace:
> [   32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
> [   32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
> [   32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
> [   32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
> [   32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
> [   32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
> [   32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
> [   32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
> [   32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
> [...]
> 
> This is triggered by the use of virt_to_page() on a module address,
> which ends to pointing to Nowhereland if you're lucky, or corrupt
> your precious data if not.
> 
> This patch fixes the logic by mimicking what is done on arm:
> - If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
>   use vmalloc_to_page().
> - If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
>   use virt_to_page().
> - Otherwise, use the provided address, as we can write to it directly.
> 
> Tested on 4.0-rc1 as a KVM guest.
> 
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Laura Abbott <lauraa@codeaurora.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

This makes sense to me:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  arch/arm64/kernel/insn.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 27d4864..c8eca88 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -87,8 +87,10 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>  
>  	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
>  		page = vmalloc_to_page(addr);
> -	else
> +	else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
>  		page = virt_to_page(addr);
> +	else
> +		return addr;
>  
>  	BUG_ON(!page);
>  	set_fixmap(fixmap, page_to_phys(page));
> -- 
> 2.1.4
> 
> 

[PATCH] arm64: Fix text patching logic when using fixmap

[Richard W.M. Jones]

On Tue, Feb 24, 2015 at 04:30:21PM +0000, Marc Zyngier wrote:
> Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
> the way we patch the kernel text, using a fixmap when the kernel or
> modules are flagged as read only.
> 
> Unfortunately, a flaw in the logic makes it fall over when patching
> modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:
> 
> [...]
> [   32.032636] Call trace:
> [   32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
> [   32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
> [   32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
> [   32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
> [   32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
> [   32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
> [   32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
> [   32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
> [   32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
> [...]
> 
> This is triggered by the use of virt_to_page() on a module address,
> which ends to pointing to Nowhereland if you're lucky, or corrupt
> your precious data if not.
> 
> This patch fixes the logic by mimicking what is done on arm:
> - If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
>   use vmalloc_to_page().
> - If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
>   use virt_to_page().
> - Otherwise, use the provided address, as we can write to it directly.
> 
> Tested on 4.0-rc1 as a KVM guest.
> 
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Laura Abbott <lauraa@codeaurora.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Tested and works for me, thanks!  Therefore:

Tested-by: Richard W.M. Jones <rjones@redhat.com>

Rich.

>  arch/arm64/kernel/insn.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 27d4864..c8eca88 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -87,8 +87,10 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>  
>  	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
>  		page = vmalloc_to_page(addr);
> -	else
> +	else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
>  		page = virt_to_page(addr);
> +	else
> +		return addr;
>  
>  	BUG_ON(!page);
>  	set_fixmap(fixmap, page_to_phys(page));
> -- 
> 2.1.4

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v

[PATCH] arm64: Fix text patching logic when using fixmap

[Laura Abbott]

On 2/24/2015 8:30 AM, Marc Zyngier wrote:
> Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
> the way we patch the kernel text, using a fixmap when the kernel or
> modules are flagged as read only.
>
> Unfortunately, a flaw in the logic makes it fall over when patching
> modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:
>
> [...]
> [   32.032636] Call trace:
> [   32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
> [   32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
> [   32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
> [   32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
> [   32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
> [   32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
> [   32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
> [   32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
> [   32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
> [...]
>
> This is triggered by the use of virt_to_page() on a module address,
> which ends to pointing to Nowhereland if you're lucky, or corrupt
> your precious data if not.
>
> This patch fixes the logic by mimicking what is done on arm:
> - If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
>    use vmalloc_to_page().
> - If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
>    use virt_to_page().
> - Otherwise, use the provided address, as we can write to it directly.
>
> Tested on 4.0-rc1 as a KVM guest.
>
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Laura Abbott <lauraa@codeaurora.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>   arch/arm64/kernel/insn.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 27d4864..c8eca88 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -87,8 +87,10 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>
>   	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
>   		page = vmalloc_to_page(addr);
> -	else
> +	else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
>   		page = virt_to_page(addr);
> +	else
> +		return addr;
>
>   	BUG_ON(!page);
>   	set_fixmap(fixmap, page_to_phys(page));
>

Looks like I dropped this incorrectly between v6 and v7.

Acked-by: Laura Abbott <lauraa@codeaurora.org>

-- 
Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH] arm64: Fix text patching logic when using fixmap

[Jon Masters]

On 02/24/2015 11:30 AM, Marc Zyngier wrote:
> Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
> the way we patch the kernel text, using a fixmap when the kernel or
> modules are flagged as read only.
> 
> Unfortunately, a flaw in the logic makes it fall over when patching
> modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:
> 
> [...]
> [   32.032636] Call trace:
> [   32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
> [   32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
> [   32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
> [   32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
> [   32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
> [   32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
> [   32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
> [   32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
> [   32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
> [...]
> 
> This is triggered by the use of virt_to_page() on a module address,
> which ends to pointing to Nowhereland if you're lucky, or corrupt
> your precious data if not.
> 
> This patch fixes the logic by mimicking what is done on arm:
> - If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
>   use vmalloc_to_page().
> - If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
>   use virt_to_page().
> - Otherwise, use the provided address, as we can write to it directly.
> 
> Tested on 4.0-rc1 as a KVM guest.
> 
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Laura Abbott <lauraa@codeaurora.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

This fixes a crash on boot in the AHCI driver experienced by a test
Fedora Hosted arm64 kernel when running on various platforms.

Tested by me on AMD Seattle and confirmed fixing the issue.

Tested-by: Jon Masters <jcm@redhat.com>

> ---
>  arch/arm64/kernel/insn.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 27d4864..c8eca88 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -87,8 +87,10 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>  
>  	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
>  		page = vmalloc_to_page(addr);
> -	else
> +	else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
>  		page = virt_to_page(addr);
> +	else
> +		return addr;
>  
>  	BUG_ON(!page);
>  	set_fixmap(fixmap, page_to_phys(page));
> 

[PATCH] arm64: Fix text patching logic when using fixmap

[Jon Masters]

On 02/27/2015 08:25 AM, Jon Masters wrote:
> On 02/24/2015 11:30 AM, Marc Zyngier wrote:
>> Patch 2f896d586610 ("arm64: use fixmap for text patching") changed
>> the way we patch the kernel text, using a fixmap when the kernel or
>> modules are flagged as read only.
>>
>> Unfortunately, a flaw in the logic makes it fall over when patching
>> modules without CONFIG_DEBUG_SET_MODULE_RONX enabled:
>>
>> [...]
>> [   32.032636] Call trace:
>> [   32.032716] [<fffffe00003da0dc>] __copy_to_user+0x2c/0x60
>> [   32.032837] [<fffffe0000099f08>] __aarch64_insn_write+0x94/0xf8
>> [   32.033027] [<fffffe000009a0a0>] aarch64_insn_patch_text_nosync+0x18/0x58
>> [   32.033200] [<fffffe000009c3ec>] ftrace_modify_code+0x58/0x84
>> [   32.033363] [<fffffe000009c4e4>] ftrace_make_nop+0x3c/0x58
>> [   32.033532] [<fffffe0000164420>] ftrace_process_locs+0x3d0/0x5c8
>> [   32.033709] [<fffffe00001661cc>] ftrace_module_init+0x28/0x34
>> [   32.033882] [<fffffe0000135148>] load_module+0xbb8/0xfc4
>> [   32.034044] [<fffffe0000135714>] SyS_finit_module+0x94/0xc4
>> [...]
>>
>> This is triggered by the use of virt_to_page() on a module address,
>> which ends to pointing to Nowhereland if you're lucky, or corrupt
>> your precious data if not.
>>
>> This patch fixes the logic by mimicking what is done on arm:
>> - If we're patching a module and CONFIG_DEBUG_SET_MODULE_RONX is set,
>>   use vmalloc_to_page().
>> - If we're patching the kernel and CONFIG_DEBUG_RODATA is set,
>>   use virt_to_page().
>> - Otherwise, use the provided address, as we can write to it directly.
>>
>> Tested on 4.0-rc1 as a KVM guest.
>>
>> Reported-by: Richard W.M. Jones <rjones@redhat.com>
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Laura Abbott <lauraa@codeaurora.org>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> 
> This fixes a crash on boot in the AHCI driver experienced by a test
> Fedora Hosted arm64 kernel when running on various platforms.
> 
> Tested by me on AMD Seattle and confirmed fixing the issue.
> 
> Tested-by: Jon Masters <jcm@redhat.com>

(In case anyone cares also tested on APM Mustang and it fixes the same)