diff options
| author | Kees Cook <keescook@chromium.org> | 2022-02-16 12:05:28 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2022-02-25 18:20:11 -0800 |
| commit | 2792d84e6da5e0fd7d3b22fd70bc69b7ee263609 (patch) | |
| tree | 44aab0a09e06fc25131dbac9b427cc5cce71e244 /arch/powerpc/Kconfig | |
| parent | efa90c11f62e6b7252fb75efe2787056872a627c (diff) | |
usercopy: Check valid lifetime via stack depth
One of the things that CONFIG_HARDENED_USERCOPY sanity-checks is whether
an object that is about to be copied to/from userspace is overlapping
the stack at all. If it is, it performs a number of inexpensive
bounds checks. One of the finer-grained checks is whether an object
crosses stack frames within the stack region. Doing this on x86 with
CONFIG_FRAME_POINTER was cheap/easy. Doing it with ORC was deemed too
heavy, and was left out (a while ago), leaving the courser whole-stack
check.
The LKDTM tests USERCOPY_STACK_FRAME_TO and USERCOPY_STACK_FRAME_FROM
try to exercise these cross-frame cases to validate the defense is
working. They have been failing ever since ORC was added (which was
expected). While Muhammad was investigating various LKDTM failures[1],
he asked me for additional details on them, and I realized that when
exact stack frame boundary checking is not available (i.e. everything
except x86 with FRAME_POINTER), it could check if a stack object is at
least "current depth valid", in the sense that any object within the
stack region but not between start-of-stack and current_stack_pointer
should be considered unavailable (i.e. its lifetime is from a call no
longer present on the stack).
Introduce ARCH_HAS_CURRENT_STACK_POINTER to track which architectures
have actually implemented the common global register alias.
Additionally report usercopy bounds checking failures with an offset
from current_stack_pointer, which may assist with diagnosing failures.
The LKDTM USERCOPY_STACK_FRAME_TO and USERCOPY_STACK_FRAME_FROM tests
(once slightly adjusted in a separate patch) pass again with this fixed.
[1] https://github.com/kernelci/kernelci-project/issues/84
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Reported-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v1: https://lore.kernel.org/lkml/20220216201449.2087956-1-keescook@chromium.org
v2: https://lore.kernel.org/lkml/20220224060342.1855457-1-keescook@chromium.org
v3: https://lore.kernel.org/lkml/20220225173345.3358109-1-keescook@chromium.org
v4: - improve commit log (akpm)
Diffstat (limited to 'arch/powerpc/Kconfig')
| -rw-r--r-- | arch/powerpc/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index b779603978e1..7e7387bd7d53 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -108,6 +108,7 @@ config PPC select ARCH_ENABLE_MEMORY_HOTPLUG select ARCH_ENABLE_MEMORY_HOTREMOVE select ARCH_HAS_COPY_MC if PPC64 + select ARCH_HAS_CURRENT_STACK_POINTER select ARCH_HAS_DEBUG_VIRTUAL select ARCH_HAS_DEBUG_VM_PGTABLE select ARCH_HAS_DEBUG_WX if STRICT_KERNEL_RWX |