Use cmpxchg instead of a spinlock in scs_check_usage() to avoid
deadlocks.
Bug: 157781894
Change-Id: I1701ccaf25fdbd34ce4798c6f93e220b1565fb34
(cherry picked from commit e929fb3f34)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
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 <keescook@chromium.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
