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FROMLIST: add support for Clang's Shadow Call Stack (SCS)

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This change adds generic support for Clang's Shadow Call Stack,
which uses a shadow stack to protect return addresses from being
overwritten by an attacker. Details are available here:

  https://clang.llvm.org/docs/ShadowCallStack.html

Note that security guarantees in the kernel differ from the
ones documented for user space. The kernel must store addresses
of shadow stacks used by other tasks and interrupt handlers in
memory, which means an attacker capable reading and writing
arbitrary memory may be able to locate them and hijack control
flow by modifying shadow stacks that are not currently in use.

Bug: 145210207
Change-Id: I2a8ba6a3decac50c169731c3121c9dcab96621d2
(am from https://lore.kernel.org/patchwork/patch/1149054/)
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Miguel Ojeda <[email protected]>
Signed-off-by: Sami Tolvanen <[email protected]>
This commit is contained in:
Sami Tolvanen 2018-05-02 10:44:59 -07:00
commit ff9de73a0a
10 changed files with 313 additions and 0 deletions
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34
arch/Kconfig
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@ -521,6 +521,40 @@ config STACKPROTECTOR_STRONG
about 20% of all kernel functions, which increases the kernel code
size by about 2%.
config ARCH_SUPPORTS_SHADOW_CALL_STACK
bool
help
An architecture should select this if it supports Clang's Shadow
Call Stack, has asm/scs.h, and implements runtime support for shadow
stack switching.
config SHADOW_CALL_STACK
bool "Clang Shadow Call Stack"
depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
help
This option enables Clang's Shadow Call Stack, which uses a
shadow stack to protect function return addresses from being
overwritten by an attacker. More information can be found from
Clang's documentation:
https://clang.llvm.org/docs/ShadowCallStack.html
Note that security guarantees in the kernel differ from the ones
documented for user space. The kernel must store addresses of shadow
stacks used by other tasks and interrupt handlers in memory, which
means an attacker capable reading and writing arbitrary memory may
be able to locate them and hijack control flow by modifying shadow
stacks that are not currently in use.
config SHADOW_CALL_STACK_VMAP
bool "Use virtually mapped shadow call stacks"
depends on SHADOW_CALL_STACK
help
Use virtually mapped shadow call stacks. Selecting this option
provides better stack exhaustion protection, but increases per-thread
memory consumption as a full page is allocated for each shadow stack.
config HAVE_ARCH_WITHIN_STACK_FRAMES
bool
help