Re: [PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
Hi Kamal, On Mon, Jul 2, 2018 at 1:14 PM, Kamal Mostafa wrote: > On Fri, Jun 29, 2018 at 01:27:08PM -0700, Kees Cook wrote: >> Do the lkdtm tests for usercopy correctly halt the kernel thread if >> CONFIG_BUG is removed? > > Yes, they do... Perfect, thanks for double-checking! I'll apply this to my tree. -Kees -- Kees Cook Pixel Security
Re: [PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
Hi Kamal, On Mon, Jul 2, 2018 at 1:14 PM, Kamal Mostafa wrote: > On Fri, Jun 29, 2018 at 01:27:08PM -0700, Kees Cook wrote: >> Do the lkdtm tests for usercopy correctly halt the kernel thread if >> CONFIG_BUG is removed? > > Yes, they do... Perfect, thanks for double-checking! I'll apply this to my tree. -Kees -- Kees Cook Pixel Security
Re: [PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
On Fri, Jun 29, 2018 at 01:27:08PM -0700, Kees Cook wrote:
> On Fri, Jun 29, 2018 at 1:04 PM, Kamal Mostafa wrote:
> > Allows for CONFIG_HARDENED_USERCOPY without CONFIG_BUG.
> >
> > Signed-off-by: Kamal Mostafa
> > ---
> > security/Kconfig | 1 -
> > 1 file changed, 1 deletion(-)
> >
> > diff --git a/security/Kconfig b/security/Kconfig
> > index c430206..7667774 100644
> > --- a/security/Kconfig
> > +++ b/security/Kconfig
> > @@ -153,7 +153,6 @@ config HAVE_HARDENED_USERCOPY_ALLOCATOR
> > config HARDENED_USERCOPY
> > bool "Harden memory copies between kernel and userspace"
> > depends on HAVE_HARDENED_USERCOPY_ALLOCATOR
> > - select BUG
> > imply STRICT_DEVMEM
> > help
> > This option checks for obviously wrong memory regions when
>
> Do the lkdtm tests for usercopy correctly halt the kernel thread if
> CONFIG_BUG is removed?
>
Yes, they do...
With this config (specifically disabling 'FALLBACK'):
CONFIG_HARDENED_USERCOPY=y
# CONFIG_HARDENED_USERCOPY_FALLBACK is not set
# CONFIG_BUG is not set
I ran the usercopy tests as follows:
modprobe lkdtm
cd /sys/kernel/debug/provoke-crash
cat DIRECT | grep USERCOPY | while read x ; do echo $x | tee DIRECT || echo
$?; done
Resulting in this command line output:
USERCOPY_HEAP_SIZE_TO
139
USERCOPY_HEAP_SIZE_FROM
139
USERCOPY_HEAP_WHITELIST_TO
139
USERCOPY_HEAP_WHITELIST_FROM
139
USERCOPY_STACK_FRAME_TO
139
USERCOPY_STACK_FRAME_FROM
139
USERCOPY_STACK_BEYOND
139
USERCOPY_KERNEL
139
Each test case yields kernel log output like:
lkdtm: Performing direct entry USERCOPY_HEAP_SIZE_TO
lkdtm: attempting good copy_to_user of correct size
lkdtm: attempting bad copy_to_user of too large size
usercopy: Kernel memory exposure attempt detected from SLUB object
'kmalloc-1024' (offset 16, size 1024)!
invalid opcode: [#17] SMP PTI
... {panic dump} ...
Each 'tee' gets terminated with SIGSEGV and no instances appear of the
lkdtm/usercopy.c warning "copy_{to/from}_user failed, but lacked Oops".
If I leave CONFIG_HARDENED_USERCOPY_FALLBACK=y then the pair of
WHITELIST tests don't trigger a panic or SIGSEGV, as expected.
-Kamal
Re: [PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
On Fri, Jun 29, 2018 at 01:27:08PM -0700, Kees Cook wrote:
> On Fri, Jun 29, 2018 at 1:04 PM, Kamal Mostafa wrote:
> > Allows for CONFIG_HARDENED_USERCOPY without CONFIG_BUG.
> >
> > Signed-off-by: Kamal Mostafa
> > ---
> > security/Kconfig | 1 -
> > 1 file changed, 1 deletion(-)
> >
> > diff --git a/security/Kconfig b/security/Kconfig
> > index c430206..7667774 100644
> > --- a/security/Kconfig
> > +++ b/security/Kconfig
> > @@ -153,7 +153,6 @@ config HAVE_HARDENED_USERCOPY_ALLOCATOR
> > config HARDENED_USERCOPY
> > bool "Harden memory copies between kernel and userspace"
> > depends on HAVE_HARDENED_USERCOPY_ALLOCATOR
> > - select BUG
> > imply STRICT_DEVMEM
> > help
> > This option checks for obviously wrong memory regions when
>
> Do the lkdtm tests for usercopy correctly halt the kernel thread if
> CONFIG_BUG is removed?
>
Yes, they do...
With this config (specifically disabling 'FALLBACK'):
CONFIG_HARDENED_USERCOPY=y
# CONFIG_HARDENED_USERCOPY_FALLBACK is not set
# CONFIG_BUG is not set
I ran the usercopy tests as follows:
modprobe lkdtm
cd /sys/kernel/debug/provoke-crash
cat DIRECT | grep USERCOPY | while read x ; do echo $x | tee DIRECT || echo
$?; done
Resulting in this command line output:
USERCOPY_HEAP_SIZE_TO
139
USERCOPY_HEAP_SIZE_FROM
139
USERCOPY_HEAP_WHITELIST_TO
139
USERCOPY_HEAP_WHITELIST_FROM
139
USERCOPY_STACK_FRAME_TO
139
USERCOPY_STACK_FRAME_FROM
139
USERCOPY_STACK_BEYOND
139
USERCOPY_KERNEL
139
Each test case yields kernel log output like:
lkdtm: Performing direct entry USERCOPY_HEAP_SIZE_TO
lkdtm: attempting good copy_to_user of correct size
lkdtm: attempting bad copy_to_user of too large size
usercopy: Kernel memory exposure attempt detected from SLUB object
'kmalloc-1024' (offset 16, size 1024)!
invalid opcode: [#17] SMP PTI
... {panic dump} ...
Each 'tee' gets terminated with SIGSEGV and no instances appear of the
lkdtm/usercopy.c warning "copy_{to/from}_user failed, but lacked Oops".
If I leave CONFIG_HARDENED_USERCOPY_FALLBACK=y then the pair of
WHITELIST tests don't trigger a panic or SIGSEGV, as expected.
-Kamal
Re: [PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
On Fri, Jun 29, 2018 at 1:04 PM, Kamal Mostafa wrote: > Allows for CONFIG_HARDENED_USERCOPY without CONFIG_BUG. > > Signed-off-by: Kamal Mostafa > --- > security/Kconfig | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/security/Kconfig b/security/Kconfig > index c430206..7667774 100644 > --- a/security/Kconfig > +++ b/security/Kconfig > @@ -153,7 +153,6 @@ config HAVE_HARDENED_USERCOPY_ALLOCATOR > config HARDENED_USERCOPY > bool "Harden memory copies between kernel and userspace" > depends on HAVE_HARDENED_USERCOPY_ALLOCATOR > - select BUG > imply STRICT_DEVMEM > help > This option checks for obviously wrong memory regions when Do the lkdtm tests for usercopy correctly halt the kernel thread if CONFIG_BUG is removed? -Kees -- Kees Cook Pixel Security
Re: [PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
On Fri, Jun 29, 2018 at 1:04 PM, Kamal Mostafa wrote: > Allows for CONFIG_HARDENED_USERCOPY without CONFIG_BUG. > > Signed-off-by: Kamal Mostafa > --- > security/Kconfig | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/security/Kconfig b/security/Kconfig > index c430206..7667774 100644 > --- a/security/Kconfig > +++ b/security/Kconfig > @@ -153,7 +153,6 @@ config HAVE_HARDENED_USERCOPY_ALLOCATOR > config HARDENED_USERCOPY > bool "Harden memory copies between kernel and userspace" > depends on HAVE_HARDENED_USERCOPY_ALLOCATOR > - select BUG > imply STRICT_DEVMEM > help > This option checks for obviously wrong memory regions when Do the lkdtm tests for usercopy correctly halt the kernel thread if CONFIG_BUG is removed? -Kees -- Kees Cook Pixel Security
[PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
Allows for CONFIG_HARDENED_USERCOPY without CONFIG_BUG. Signed-off-by: Kamal Mostafa --- security/Kconfig | 1 - 1 file changed, 1 deletion(-) diff --git a/security/Kconfig b/security/Kconfig index c430206..7667774 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -153,7 +153,6 @@ config HAVE_HARDENED_USERCOPY_ALLOCATOR config HARDENED_USERCOPY bool "Harden memory copies between kernel and userspace" depends on HAVE_HARDENED_USERCOPY_ALLOCATOR - select BUG imply STRICT_DEVMEM help This option checks for obviously wrong memory regions when -- 2.7.4
[PATCH] security: CONFIG_HARDENED_USERCOPY does not need to select BUG
Allows for CONFIG_HARDENED_USERCOPY without CONFIG_BUG. Signed-off-by: Kamal Mostafa --- security/Kconfig | 1 - 1 file changed, 1 deletion(-) diff --git a/security/Kconfig b/security/Kconfig index c430206..7667774 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -153,7 +153,6 @@ config HAVE_HARDENED_USERCOPY_ALLOCATOR config HARDENED_USERCOPY bool "Harden memory copies between kernel and userspace" depends on HAVE_HARDENED_USERCOPY_ALLOCATOR - select BUG imply STRICT_DEVMEM help This option checks for obviously wrong memory regions when -- 2.7.4
